That amp is beautiful. What a masterpiece of 1960s electronics engineering. Look at the holes in the chassis around the tubes to dissipate heat, even! This was made by serious people.
I presented this to my friend Jerry @ Kroker Amps. He's been doing this type of design/work for most of his 70 years. He said the ultra linear output transformer is perfect for a low gain acoustic guitar amp, something to consider if you have one of these. He also said, just like Uncle Doug, that with pedals this would work fine with a solid body electric.. The transformer layout is very nice (they are away from each other OT & PT) and it has the 7189 tube option which are the more robust EL84 tubes. Thanks Uncle Doug for your videos!
That amp really is a work of art and remarkably unmolested given its age. Thanks for taking us along. I will definitely be on the lookout for PA's that can be rebuilt for guitar.
Cheers! Way back in the sixties, me and my musical mates were using radios and the like for guitar amps. We used to just wire the signal up to the top terminal on the first valve! Of course, if you got a radio with an input for the old moving coil 78 players, you were away!
bills48321 You're right, Bill. I will definitely keep that in mind for a future video. Meanwhile you might enjoy the video featuring tone improvement in a Gibson GA35-RVT amp. The change in the Newcomb was similar, but not quite as pronounced.
Great job with this one! This unit looks a lot like a Bogen Challenger PA that I rebuilt years ago into a guitar amp as a teen. It’s fun learning all of the tricks of the trade at that age because they stick in one’s head never to be forgotten. Love your great sense of humor that you inject in these videos.
Years ago,I had an old Bogen PA amp I thought about converting to a guitar amp.Around the same time,I saw a '30s or '40s vintage Bell and Howell Filmosound speaker and cabinet.I could have gotten it for next to nothing.I enjoy your videos.
Uncle Doug I got me one! The E40 model with 4 X EL84s! WOOHOOO! It's been recapped with new tubes. With a tube preamp, they REALLY open up. I'll be able to use the 4 ohm tap with 2 Alnico spkrs I've had laying around. Jangle Chime and Glassy Tone for Days.
You have a good sense Of figuring out things Also a master of expression. Like those chicken Heads clucking away On the front. Yes I saw that movie 2001 space Odyssey In a drive in theatre Back in the 70s. Also saw the sequel A few years later on TV. I have seen this Newcomb amp video twice thought I would See it again. Your are a Jewel of a man for amp mods and repair. Dwight
Very well done Uncle Doug. The amp sounds superb and Rusty is quite the gentleman. I just picked up two beautiful Newcomb's. A KX-6a Pre Amp and a KX-25 Amp using two 6L6 outputs. I can't wait to get them restored. Another thumbs-up from me to you.
+TheRudydog1 Thanks so much, Rudy. Rusty and I really appreciate your kind words. Congratulations on the newly acquired Newcombs and best of luck with your restoration of them.
+Jonathan Castillo Thanks so much, Jon. The camera microphone really doesn't do justice to any of the amps I record. Some day, I would like to step up to a camera with an input jack for a separate, better quality, microphone.
I don't know but if I were a little under the weather after 4 liters of MD 20-20 I would probably want to cut the power cord off of it, lol. Great sounding amp!
Well, that's a beautiful piece of equipment you got there. They did a great engineering job. Another good tip for making a Hi-Fi amp sound more "guitar friendly", is to disconnect both of the screens from their output transformer tap, and make them run directly from the B+ through a resistor. You could probably hear the Hi-Fi people screaming that it is a heresy while making these changes. Another great video, always enjoy watching. I think Rusty is ready for Hollywood.
Thanks, Nixo. I'm glad you share my enthusiasm for the mighty Newcomb E-20. I'll keep your suggestion in mind for future modification. Don't build up Rusty's ego too much, his agent will probably hit me up for a big raise :)
Uncle Doug you have an academic skill that is a delight for the disciplined educated mind with the relaxing touch of Rusty always by your side ... congratulations . e.b.
I just bought one in great condition off fleaBay, with all the tubes. Can't wait to have it checked out by my tech friend. Lots of spread between the power and output transformers. I can't believe it didn't go past $85, good for me. Love the old tube amps even if their design layout can sometimes be wacky, this layout looks pretty decent.
Yeah, it does look like a Seeburg after that paint with it's nice angles. I used to have a D-80 in 2005. Hard to believe it's been so long. I'll have to get another one for a hobby soon.
Thanks, BT. I'm glad there are others who appreciate good, old-fashioned point-to-point wiring. It is indeed an art.....and (unfortunately) rapidly diminishing.
Hahaha!!!! Mad Dog 20/20. I haven't even SEEN a bottle of that stuff since I was in high school. Hilarious. Those preset indicators on the knobs are cool as hell! That's actually a really great idea. First time I've ever seen that.
Mad Dog, Ripple, and Country Club Malt Liquor were standard refreshments at all social gatherings back in the old days.....when "only the best would do" :) On a more sober subject, yes, the presets are very clever.....much better than the indelible ink lines you see scrawled on amps from time to time.
i just love the sound of a hi fi amp (pa amps in general are hi fi ready) with my guitar amp modeler positioned in front of the input i have a stromberg carlsen au-58 b from 1955 and omg just plain w/o the modeler is bg and throaty as heck .. as a jazz player i find it wonderful..no additional mods for me tyvm
Uncle Doug I got this one's big brother, the E-40 model modded with guitar input and spkr out jacks. HUMs w/out anything plugged in. Turning up the Bass ctrl, the HUM is horrible. Seller paid to ship it back and have his tech look at it. That tech can't handle the problem, so seller is paying to ship it to a tube amp tech we both know and respect. I look forward to giving a happy update soon.
@@UncleDoug FIXED! WOOHOOO! Using a tube preamp/compressor it works great plugged into the Aux input. Thanks for inspiring me to get back into TUBE Heaven.
Garard, yes Sir! Later went bigtime with Techniques.... I wish I could have heard the tone b4 and after. But the after sounds pretty nice!! I remember Bogan PAs...Nice
I love these amp shows ... Absolutely Brilliant Uncle Doug ... Hopefully I can meet you some time on my trip to texas where my cousin lives ... That would be sooo sooo cool ... Another Professionally explained video And valued information ... ))) ... Say Hey to Rusty And kitty for me ... ))) ... P.S. great humor ... lol
This amp sounds great. Who needs distortion or effekt (pedals) when you have a so clean reproduktion Nice for a change to hear how clean a guitar can sound.
@@UncleDougYou know, I still have my Newcomb D-10 that I need to recap and make into an instrument amp. That i have both guitars and basses and would love to be able to use it with both. I'm thinking that clean, hi fi tone would give some sweet, clean tones for a bass.
very cool. my neighbor gave me his dad's old newcomb e 10 amp. it has the same phono input as yours, and a square four contact mic input. a similar speaker setup with the ohm choices, although i think you just pin the speaker connections to that round selector socket. one of these days i will have to see if i can convert it to a little guitar amp head.
These are used at square dances! They LOVE mid-range speakers for some reason! One of the models of speakers that are popular are called '"Yak Stacks" - several small midrange drivers in a column .
Thank you Doug for another very cool video! Someone said it right, Rusty really is the cherry on these lovely tube sundaes! Keep 'em coming, I am learning a lot.
Yes, indeed, Roger. Looking at the schematic of the E-20, the top center tube is the Phase Inverter. Its plate drives the grid of the upper output tube, while its cathode (opposite phase) drives the grid of the lower output tube. It's also known as a Cathodyne Phase Inverter. Good call !! Now for a second test, take a look at the Newcomb Model G-12 schematic (either in my video on this model or download it on the Internet). Same manufacturer, but what type of P.I. does it use? Warning: It's a little tricky.
Uncle Doug I think it's a paraphase, because it splits the signal coming off the 6SF5 tube plate and sends it: 1. to the first power tube, and 2. to the 2nd 1/2 of the 6SC7 preamp tube's grid and then connects that plate to the 2nd power tube. And there's a resistor going to ground just before the signal hits the V1 grid, to bring the signal down in balance w/ the other signal. The 6SF5 has only one triode, so it couldn't be used to do both sides of the phase inversion; but the other 1/2 of the 6SC7 was available. I suppose one could connect the 6SF5's cathode to the cathode of the 6SC7 and get a long-tailed pair PI?
mudylafeet Thanks again, Mudy. I hope Rusty and I can keep you laughing, and that the tech discussions continue to make schematics easier to understand. :)
I probably also would have liked the "sickly pea green" you painted over, but I love the color, and it looks like it would be the original color. I didn't know there was color matched spraypaint for Seeburg jukeboxes, but I've got to get my hands on something like that- there just aren't enough good rich colors in newer paint it seems. I used to own an AMI D-80 juke that I restored. Seems that Seeburgs are the best jukebox, I'd like to own one someday.
+Joel Thomas Thanks, Joel.....glad you liked it. I bought the spray paint many years ago (and it still works !!) when I was restoring vintage jukeboxes as a full-time business. Back then, all sorts of original and good reproduction parts were readily available. Now, due to the decline in enthusiasm for old jukeboxes, the availability of parts has dwindled.
@9:00 where the red caps are in place, mine has components there. They look like capacitors, but according to the labeling on the chassis, I’m assuming they are transformers.
I checked it out again, and yep, they’re transformers . It shows a pin out and part number on them too. I can PM a picture if you like. Just searched via google “tr-91 Newcomb”. You can see and image of one there as well.
I did the search and you're right, they are input transformers for microphones. I guess they alter the impedance of the circuit to suit a microphone. They also seem to be rather valuable......so you are a lucky guy.
Uncle Doug, if it does not affect guitar output in a good way, I may keep them unplugged for now. I will try both ways once I put in the 50mfd 100 volt cap that you have added as well.
I actually use a ‘62 and ‘67 12” Oxford speaker out of a Thomas organ and they’re absolutely magnificent mated to my Vox ac30. Also, historically, Thomas put oxfords into the very early vox ac30s, as licensed from Vox.
Those would have an even wider range of frequency reproduction capability than guitar amp speakers (at least theoretically -- more octaves). More likely, such speakers would do fine in either instrument amp. It's the voice speakers that are so disappointing.
What a wonderful channel! I HAD to subscribe. Anybody who uses the word "snazzy" is definitely from my generation. Thank you for all the wonderful videos that will surely keep me occupied in my Denture Cream years. Cheers!
Wow.....thanks so much, Duke. Welcome aboard !! I was a teacher for many years and would (from habit) use old phrases like "snazzy", "what a drag", "I'm hip", etc. during classroom discussions. The kids loved it. I would hear them later using these terms on the playground. Good expressions never die, they just skip a generation :)
Uncle Doug Thanks for the reply. I just watched your 12 amp comparison video. They were all "snazzy" but the Kustom was downright "boss". Wish I still had mine! It's sad they were "frowned upon " back in the day.
I guess because they're transistorized rather than tube, some people looked down on Kustom amps, but quite a few famous musicians used them on stage. I just love their looks.....completely unique (and "far out") :)
I love how Rusty requires your sense of humor to be set to "eleven" at all times! Most informative as well. Thanks Rusty for keeping him on his toes! However, instead of valium, perhaps you recommend a quaalude next time?
Uncle Doug, There is an amp that has been in my dad's attic for as long as I can remember. With it, is a metal plate with oiling instructions and indicates it is a Hammond model M amplifier, serial number 11836, 115 volts AC, 60 cycles, 93 console watts. There is one larger transformer that has no corrosion, as well as a smaller one, also without corrosion, that has AO-20936-0. The tubes look okay, and are as follows: 5U4, 6BA6, 6V6, 6V6, 6SC7, 6J7, 6J5, & 6SJ7. On the "front" are various screws, that look like wires have been attached, as well as a couple of what looks like RCA inputs. The best I could read with my old man eyes: "Pedal Cutoff" "Key SW" "Decay SW" "Sus SW" "Pedal In" "Voice Coil" "Ped" "Att-Key" "VIB"(?) The RCA looking inputs have (best I can tell) "Radio Phono" & "Spec Input" So……would this make a good guitar amplifier? I know absolutely nothing about electronics, but do play guitar, and love the different colors and temperatures of tones that tubes can produce. I am not asking how to do what needs to be done, because I am sure I will be finding someone to be with me every step I take…..I've just not seen anything other than amplifiers from M3's, M2's, or M100's anywhere. I DID, however, find the schematics, block diagrams, wiring for the organ itself….but what is the amp called? AO-20936-0??? Thanks, and sorry for asking so much ! Ke & Ri
Greetings and thanks, Flip. I agree, the tone is indeed "Fendery". These E-Series Newcomb PA Amps make excellent guitar amps....and at a bargain price.
I guess you wouldn't want to mess with it too much, but it might be interesting to have a 3PDT switch to wire the output tubes connected to the plate supply for pentode operation, the UL screen tap, or tp the plates themselves for triode operation. Or put a switch to put the input triodes in series.
Unca-Doug has hit the vintage market jackpot again. I could spend days messing around with various effect pedals with this jewel of an amp but I'm curious as to the original PA duals. . . it looked like there was room enough in the two cabinets to wire up a higher frequency tweeter in each. Have you considered this? I'd love to hear it if you do. There appears to be plenty of power to drive that configuration. Thanks for posting an excellent presentation!
Greetings, CB. Your idea of adding tweeters is an interesting one, but the main deficiency with these speakers is bass.....there isn't much at all. The tone of the original speakers reminds of the piped in "music" at McDonald's or the (endless) paging at Home Depot. Being old fashioned, I tend to like a lot of warmth and bass in my guitar tone, and the only way I could get it was to shift to a more guitar-oriented speaker. I really appreciate your time, interest, and input. Thanks so much !!
Uncle Doug Just curious - is the frequency response of the speakers low end capability more a function of the circuit elements as they're configured or the speakers themselves? Granted they are old, but I can't help but think that 12" ceramics of this quality can't handle a little bottom? I'm not talking that windstorm generated 6 inches off the floor bass which causes building foundations to decay. . . perhaps as an acoustic-electric guitar rig or, dare I suggest, violin?
TheCarablanco A good question, CB. I think it's the speakers themselves. I really tried to use the original speakers, but they simply can't cope with the bass frequencies that a guitar generates. The ceramic magnets are rather small and the cones suspension is a little flimsy. They tend to flap around and sound pretty bad, even at moderate volume. I think the proof of this is that when the same circuit is connected to a large-magnet, firmly suspended 12" guitar speaker.....it sounds great.
awesome doug! i picked up a bogen challenger cha-20 pa amp at a yard sale for 50 bucks a while back. i did similar modifications to turn it into a guitar amp (including adding a bias cap) and it sounded great! I wasn't so lucky with my tubes though. all tubes but the 6v6's on my amp were shot and so were the electrolytics. cant wait for more videos!
Greetings, Tom. I've never owned a Bogen amp, but I understand they are of very good quality. Sorry about the bad tubes, but for $50, you still hit a major home run :)
Uncle Doug, I always read how the location and treatment of filament wires is crucial to lessen hum, but anytime I see a point-to-point amp (vs. turret/eyelet board), the filaments are usually not twisted, they run near the pots, etc. So, how do point-to-point amps get away with that? Tricks like DC elevation? Or is it really not as big a deal as people make it sound?
tgitarezam b I believe that in any well-built amp circuit, all AC wire pairs should be twisted to reduce hum, TG. Perhaps some builders skip these details, but like any complex undertaking, there is only one way to do it right.
Chicken heads look good. Early PA and school dance record player amplifier. I remember dancing in the school gym to a some kind of special occasion decoration theme and hearing Santo and Johnny's Sleepwalk coming out on each side of the the stage with these kinds of PA setups...those were the "HAPPY DAYS" with "The Fonz and Richie" ..and of course there was the "Our Miss Brooks" show where she would announce the school day's events over the school PA system. Years later I did use that 25volt secondary o/p tap (that you mention) for those older shopping centre central walkways to drive several 8 inch ceiling speakers..You could drive quite a few speakers with this method as long as each speaker had it's own individual step down transformer. Was that a few strains of "Wipeout"?
SuperCarver2011 Thanks, SC. If you're speaking of the final two tunes, they were similar versions of something I made up, with a little flamenco flair. Rusty helped me compose it :)
Uncle Doug Your trusty K-9 sidekick is very talented. However, I presume he doesn't sing along when you play those "Dog-gone blues"..LoL. I get a kick out of seeing the look he gives you when you ask him for any assistance.
Rusty is an excellent musician, assistant, and source of inspiration......but may seem reluctant to pitch in with the menial tasks. It's just his "video persona". In real life, he is a tireless worker ;)
@11:11 , you mention the ultra-linear xformer is wired to the power tubes to reduce distortion. If another 12ax7 and some resistors and capacitors in the right places, can the rick-tone tremo-drive be added to “force” distortion and add tremolo as well? Asking because I recently obtained an identical e-20 from a friend, and may want to take that extra step. Edit- I just thought of something. Since the 12ax7 is used on the two separate channels, maybe I would only modify the one side with a lower plate voltage to make distortion, feed the modded channel into the other, and maybe add a 6AU6 or something similar for tremolo instead. Not sure how I’m going to do this yet. We will see though. one more edit- reading through the comments state other ways to bypass the ultra-linear with resistors. I will be checking some Mesa-bogie schematics where it has switchable ultra-linear lines. Still may add tremolo.
The RickTone Tremo Boost can easily overdrive an amplifier into saturation. You don't need to add anything to the circuit. It can also create a Tremolo effect at the same time, if you wish.
One of your older videos that I missed somehow (I used to sign in with my company account, eRyde). Cool video Doug. Two things I noticed on the schematic. The voltage for the 6BQ5 at the plate was 360 (if I read it correctly) which is pretty high for an EL84 which has a max rating of 300v in my books (Sylvania and RCA tube manuals). Also the screen voltage is slightly higher than the plate voltage, albeit only 3 volts (again if I read it correctly). So now I'm curious as to how far you can actually push an EL84 and still maintain a decent tube life of say at least a year before it starts to degrade.
I have read the low max-PV values for 6BQ5's and 6V6's in the tube manuals and am puzzled by them, since both tubes routinely operate at much higher plate voltages than the manuals would suggest. Indeed, Fender ran the 6V6's in their BF and SF amps at well over 400V. I would suggest that PV does not determine tube life, but rather it is Plate Dissipation that is the most important criteria. As long as you keep the PD below the max for any output tube, it's useful life should not be reduced.
I just ended picking up a Multi Kord Model 125 single ended amp which appears to be from the 50's maybe? Looks to be in very nice original condition except the speaker cone is shot. Appears to have original everything else in nice shape. I actually picked this up with you in mind and would like to give it to you for all the help and kind assistance you provide to everyone in your channel. I'm an old car dog like you and have restored a lot of cars (that's why I knew so much about the 70 Mustang Boss 9). In any case, this amp seemed like the kind of thing you like and it would be my pleasure to send it to you to do with as you wish. Bert
Thanks so much, Bert. If this is purely a tube amp (no semi-conductors at all) with a power transformer (not series-filament) we would love to receive it and possibly use it for a video. Please provide your e-mail address and I will contact you directly.
@@UncleDoug I've tried to add it here twice, but the message disappears. My guess is they are filtering it out. I've added it to the "about" column on my information. Let me know if you can get it from there.
Wow, what a great find, those Mullard valves are certainly worth a lot on online auction sites. IMO, I think JJ Tesla is just as good in terms of performance although many people would disagree. As far as UL output stages go, they can be quite good for instrument amps, especially when used with EL84s as opposed to pentode mode (think of the rather jarring jangly overdrive of British Invasion rock, that's the sound of a pair of EL84s in pentode mode). In the UL connection the overdrive characteristic is a lot smoother, much more similar to a triode which gives a more mellow distortion similar to that of guitar amps using beam tetrodes, possibly even smoother. Distortion is also lower when not overdriven, producing a cleaner sound. It's all subjective anyway! You might want to watch out for that cathodyne phase inverter, they can behave a little oddly if you drive them hard.
My pleasure. I would recommend putting the PI into see saw operation instead of cathodyne for best overdrive performance, doing this gets rid of the grating anode voltage spikes on the cathodyne configuration (which will mess up the smooth OD of the UL configuration) as the cathode load goes into positive bias and conducts. You also get the benefit of reducing the cathode to heater voltage, reducing hum and improving valve life.
Just wondering what speaker was used in the demo portion. I have a Jensen P12Q that I thought, from your description, would fit in perfectly. The sound you got as the end result was pretty close to what I had in mind. Another beautiful video UD. Thanks!
You're welcome, V. You have a good ear. I was using a 1950's 12" Alnico (probably Rola) speaker, which does sound much like an early (tweed-style) Jensen. If I were to build this chassis into a combo amp or build a cab for it, the P12Q would be at the top of my list for speakers. Thanks for your input !! :)
Uncle Doug A huge YES! to the Rola speakers. I have a small collection. A very nice alternative to the Jensen's, at least in in Hammond's mind, as these were used as an alternate, and definitely not inferior speaker in their organs. The 8" Hammond Reverb Rola speakers are among my favorites. I'm looking to build a mini 4X8" cab with these. Ooooops, maybe I said too much :(
Hey Uncle Doug & Rusty, Very nice amp, will keep a look out. I was going for my blood pressure med's when I heard what the tubes were. I saw your light bulb current limiter hiding behind the amp, cool. I made one per your video, tested, works great. As always a fun and educational video. Pretty good on the guitar. Look up D'C'G trick on YT. Take Care,C.
+Cass Virgillo Thanks, Cass. I had to visit Walgreens too, but it was for some Depenz, rather than BP meds :)) Glad you enjoyed the concert and the lurking Current Limiter. Happy Holidays !!
I would love to be able to repair and modify my tube amps.. I'd also love to be able to scratch build a quartet of small Fender Champ based amplifiers for home use , linking them using a computer with my favorite amp sims and vst effects within my Sonar X3 D.A.W. which will recognize multiple interfaces simultaneously using ASIO drivers..This way i can play backing tracks within the DAW through their own interface and have the amps on two over interfaces in sync with the backing track and have as many effects changes as my heart desires with automation writing so i can just sit back and play and not have to push anything at any time..With the automation it is like having a complicated sequencer doing all the work without being complicated
@@UncleDoug Lol the way i describe things is convoluted .I could describe making buttered toast and half the people reading it would swear i somehow connected it to the signing of the " magna carta " lol..I don't have your gift of uncluttering an explanation !
I wonder why you don't see those air holes around the tubes and transformers in combination with the louvres on the bottom in guitar amps. Seems like a good way to keep exces heat under control... you'd expect to see that on small box head amplifiers but i've never seen that. It shouldn't cause interference now should it? Is it just the added labour why guitar amps don't have these?
It does seem like a wise engineering modification, Fra, but since heat rises, one could question the benefits of holes around the tubes. The main source of heat is above the chassis surface, not within it. I can see no reason why it would reduce the shielding of the circuit.
@@UncleDoug Thanks for answering. Depending on the amp chassis i think it might because of the laws of thermodynamics. A Fender style amplifier (or other brand) with the amp chassis in the top of the cabinet wouldn't benefit much i'd imagine as it would actually allow heat into the chassis but i think a bottom loaded Marshall style head actually would. Those regularly have a screen in the back or top of the head cabinet for the heat of the tubes to escape trough but no real way of sucking in cool air. The rising heat escaping trough the top/back would create a vacuum sucking fresh, cool air in trough the bottom louvre/screen and trough holes around the tubes in the chassis. I might be overthinking this and overestimating the added benefit but it does seem like a good way to cool the capacitors and tubes somewhat in small box head amps. I thought a lot about this subject because i hope to one day build a 5f2a based Princeton style circuit but in a Marshall head style chassis and cabinet as small as possible... About the size of, or, a little wider than a normal sized amp handle and was planning on using vents and holes because with a P.T, OT., choke and tubes producing heat in such a small housing i figured i could use as much cooling as possible.... If it ever happens that is..., i'm better at planning and thinking about building things than actually doing it i guess... but i digress and waisted enough of your time you could be spending on making these awesome videos already. Thanks for listening to me rant and have a good day.... give my regards to Rusty and Jack.
Uncle Doug is it that 6BR8 preamp tube coupled with that nice UltraLinear output xformer that makes this amp's sound so unique?!? For guitar it's SO 'glassy'...dunno another word for it. I can't help but think this wouldn't be too hard for me to build after seeing the underside. I had one once, had a tech rip out the tone circuit and that amp had jangle and chime for not days, but YEARS. " I MISS IT" is an understatement.
Would it make sense to connect the two preamps in series, reducing the number of inputs to one, and so utilizing all available gain stages for more distortion?
Each of the preamps is set up to accept a low voltage (i.e. less than 1V) input. If you placed them in series, the second preamp would receive a signal of much higher voltage than it was designed to accept. This would result in all sorts of distortion, as you suggest,.....but none of it would be of the "good" type.
any special advice on the heater wires when constructing an amp point to point? I notice they are not twisted together in this amp, and noise is not a problem. I have gathered all of the parts to construct DaGeezer's "Little Wing" mini-Bassman that uses 6BM8s. The chassis I want to use is a bit too small for a turret board, so I'd like to do point to point, but I'm worried about noise. Thanks!
Greetings, Jim. It's always best to tightly twist the AC wires to the tube heaters, and when you get to the tube, don't wrap around the perimeter of the tube base, but arch up, over, and straight down to the pins to which you are soldering. Good luck with your project :)
uncle doug, this kind of work fascinates me, but I'm afraid the few videos I've watched haven't turned me into an experienced and knowledgeable tech. where can I go to learn the most basic principals of these circuits and then work my way up to making my newest uncle proud?
+James King Rusty and I have posted 121 videos so far, James, and a bunch of them discuss all aspects of tube amp circuits....how they function and are designed, built, tested, etc. as well as all sorts of safety tips. I suggest that you watch some of them and see if they are helpful. Good luck :)
Do you know if there's any truth to the rumors about people like Aspen Pittman going to Russia and China and getting them to upgrade their designs and literally reverse engineer the old American and European tubes? I've been told that the new Mullards and Tung-Sols are very good re-issues, but I haven't tried any of them yet.
I have not heard these rumors, but from experience, I feel that many of the newly manufactured tubes are of excellent quality, often with superior power handling capability (higher plate voltage and current) when compared to vintage tubes. Some of the early "replica" tubes (i.e. from 10 to 20 years ago) were not so hot, but I think they're getting better and better at meeting and exceeding vintage specs. This is probably due to the huge, renewed interest in tube amplifiers and the large amounts of money being spent on them (and tubes).
I havealot of those 5y3 tubes idk if i ever tested them i have so many but used to sell tubes but now as nos tubes are getting scarce and expensive i wont be selling tubes on ebay anymore ,i only did for a few months but kinda wish i hadnt sold the 1s i did sell oh well such is life
Hi Uncle Doug. Thanks for this video. I've recently acquired the E-40 version of this amp in the same beautiful mint condition. It has the 4x EL84/6BQ5 output stage. I was wondering if it matters which of the four output tubes I should pull for a reduction in output volume. Does it matter? I intend to copy your cathode bypass mod and use this amp to power a 2x 12" blackface era Fender cab that I picked up on CL. Are there any other pointers you can give for the E-40 model?
Greetings, Slog. Congratulations on acquiring a great amp. I am completely impressed by every product I've encountered from Newcomb.....the amps are beautifully constructed and sound great. Here is an excellent site to explain the process of output tube removal: www.premierguitar.com/articles/20713-ask-amp-man-removing-output-tubes-to-reduce-power I think you will like the cathode bypass modification. I have no personal experience with the E-40 model, and really have no other modification suggestions, simply because other than sounding a bit sterile (which is improved by the CB cap) the amps have wonderful tone as-is. Best of luck with your new amp !!!
Greetings, Sorin. A "guitar friendly" speaker would have a larger magnet, a larger diameter voice coil, and a firmer suspension around the perimeter of the speaker cone, to better cope with the bass frequencies that a guitar produces. This is especially important in open-back cabinets (such as these) where there is no trapped air to moderate the excursion of the speaker cone.
Hi Uncle Doug, curious if you have any interest in converting another Newcomb pathfinder E20 to a guitar amp? i recently found this collecting dust in a shop locally and took it home.
Seeburg juke amps? I've got a Seeburg MA1-L6 amp which has been converted to a bass/guitar amp. It took me almost two years to locate a low-res and nearly useless schematic for the L6.
Greetings, Scott. As I recall from my jukebox days, the MA1-L6 amp was used in the Seeburg "Trashcan" amps from the late 1940's. There was a later HFMA1-L6 (High Fidelity) amp used in the 1950's 100-R, C, J, etc. models. I found the following schematic, which seemed rather legible: www.4tubes.com/SCHEMATICS/Music-amps/Seeburg/ma1-l6.jpg
Could the negative feedback loop have a simple switch to defeat it or should there be something else in circuit to accomplish this and (as per my usual) what did it sound like before adding the bypass cap and possibly a switch for that as well... (his eyes widen as he screams "more bells, more whistles!!") Thanx for another gem, Uncle Doug and cheers
Virtually all the schematics I use in the shop and in videos are simply downloaded from the Internet. A Google Search can turn up the schematic to just about any amp ever made. Give it a try.
hello...i have a Magnovox Playfellow amp that has been partially converted to guitar...i will send you a copy of the SAMS...it has a 1/4" input into the volume control, and I disconnected the NFB loop...can you please give some some guidance for bypassing the biasing resistor, as you did in the Newcombe??..thanks!
clearview02 You can use alligator clips to (carefully) test different value bypass caps, in parallel with existing bias resistors in the pre-amp and output tube(s). I usually start with 25uf @ 50V and see if I can hear improved tone and volume. It's a trial and error procedure, using different cap values in different locations, until you come up with a tone that you like.....generally warmer, with improved bass and gain.
Uncle Doug Thanks for your suggestion and many informative videos...i went back and watched your video on cathode bypass capacitors again--a lot of material there!...i did much the same experimentation on a PCB amp that had intermittent signal issues...disabling both the effects loop and footswitch circuits took care of the intermittent issues...i was surprised how much the signal "opened up" after disconnecting the effects loop...all those extra capacitors and resistors took a lot of "fizz" out of the sound...after that mod, i experimented with different value capacitors, to get a tone i like...but i didn't use the alligator clips, so i got lots of practice with my soldering skills!..i read somewhere that a lot of Fender's classic amp circuits from the 1950s came about from pure experimentation; as Leo was an accountant, not an electronics engineer, by prior training and vocation......
clearview02 p.s. and i wonder how much effect the mid-range driver has if you tweak the other elements as needed??...i know that Peavey used to put mid-range drivers in their tube guitar amps...Chip
Somebody is pulling your leg about Leo Fender, Chip. He was a highly experienced radio repairman and electronics whiz, who personally developed the guitars and amplifiers that made his name and company famous. In fact, he was so focused on the technical side of his company that he often neglected sales and accounting. Re the mid-range driver, most guitar amp tone circuits tend to scoop out the mid-range, because guitar pickups tend to emphasize this portion of the audio spectrum. Since we virtually never see popular guitar amps with mid-range speakers, I would tend to think they are not much of an asset.
It looks a bit like a jukebox amp. Personally i would have it restored and left it as it was originally. But that´s my opinion ;) Good work anyway and have fun with it! Thanx for sharing!
***** Thanks, Roger. I think I'll use it as a head. I have some good speakers in cabinets that work well with it. The original speaker cabs are open-backed (no bass resonance) and rather cumbersome, especially if good (heavy) guitar speakers were installed.
I think this unit was intended to be used for speech amplification at sports or at a faire. Therefore there is no need for any bass responce. Open baffle makes the unit more lightweight thus easier to carry the whole thing around. The cones of the speakers are special designed for it. You can see this by looking at the very small ferite magnet as well. It´s intended to be used only in (lo)mid to high frequency range. But with a very good efficency, well over 100dB SPL at 1W/1mtr. is typical for these speakers. If you mount a guitar speaker into this sort of cabinet it will sound awful and you´ll may end up with a blown/damaged speaker due to too much cone excursion at low end frequencies. Use only the Amp like a Head is the best thing you can do. But some Harp players will love this thing with its original speakers, because this is exactly what they are looking for. This old PA units match exactly their needs in terms of frequency response and overall sound feeling...
Thanks for the excellent and informative input, TC. Your recommendations coincide quite well with my planned use for the unit. I was, however, unaware that the tone response of this system was so suitable for harmonica use. I'll keep that in mind when seeking a new owner for it. Thanks again for your time and assistance :)
Thanks for the great video Uncle Doug! I just picked up a Newcomb M-12 55W PA amp, and am hoping to convert it to a guitar amp. It has an RCA cord that I believe is an input, but it’s the same on both ends. Can I buy a RCA-to-1/4” cord (such as at Radio Shack) and play as is, or should I convert the input? Also, I don’t know almost anything about transistors, or whether I’d need the bypass like you added for tone? Sorry about so many questions, learning a lot really fast, haha. Any info appreciated, thanks :)
You're welcome, Donny. I really can't answer all your questions without evaluating the circuit.....so I think you would be better off trying the changes you mentioned, seeing if they work, and modifying them if they don't. This is, by far, the best way to learn.
+Jonathan Castillo I have no way to host such a photo, Jon. Perhaps you take a photo of the screen at 9:20 ? I have tried this is the past and it generally works fairly well.
Greetings, Cat. I'm glad someone out there shares my slobbering enthusiasm for high quality, original, vintage tubes. More and more often, I am encountering modern replacements instead of original old RCA's, G.E.'s, etc. You could probably debate all day over whether there is really that much tonal difference between old and new......I tend to think there really is a (sometimes subtle) difference.....but finding original tubes in an amp always impresses me as strong evidence that the amp was never altered, mistreated, or excessively used. It's like finding a smooth-running, all original, Power Pack 283 under the hood of a '57 Chevy......instead of a crate 350.
Uncle Doug Sorry here but these days are gone. The market for real *good* NOS USA/JAN/German/UK tubes is about to its final close. Prizes are "through-the-roof" already. As the prizes rise some fellas tear out the Original tubes and smash it on ebay to make fast money, and sell the Amp some two weeks after without tubes to get the max$$$ out of it. For Years a´m looking for a "Jörgensen" all tube organ, its sound generator is made out of 48 ECC83 TFK tubes originally, but all i see is that some units apear on ebay they shorty rise above $1k and up. just because these tubes are in it. the winner tear out the tubes and *dump* the beauty organ *DAMN* And some NOS telefunken EL34 which I bought recently are not as good as new JJ. So what? My two cents are: there is a chance to get some good NOS tubes, western made. But i´m entirely out of this by now. As i´m very happy with new made JJ when it comes to standart tubes. When buying NOS or odd (non standart) tubes i´m always go for formally USSR types. As I found that they are much more rugged/reliable than any other (=similar) types. For instance I use GU50 (ry-50) which is the russian version of the LS50 (EL156). Where one can get the ry-50 for about $5 but the NOS europe is about $100-200 and you´re not knowing if they are really NOS or just claimed like it.... If a ry-50 fails, i *do not care* i just swap it. But with a EL156 i go nuts ;) But my 4x ry-50 Amps still got the 1st set and its doing just fine. So i´m replacing all my vintage tubes with russian equivalents. Like 807=g-807 (g-807 is even more rugged than the original US made JAN-807) or EL34 is 6P27C, EL36=6P31C and 6L6=6P3C and EL84=6P14C(-EW which is happy with 400V). Or even use tube with *no* equi like the 6C33C regulator tube. My daily HiFi Amps are Philips EL6435 (4x PE06/40N output tubes each) which cost a little fortune NOS. But replacing them with G-807 and rebiassing these Amps just work fine and I do not need to wear out the PE06/40N tubes. A set of 20 (!!) G-807 is equal to *one* NOS PE06 in terms of the prize to pay for ;)
Uncle Doug i'm a sucker for old tubes, mostly just because _they look really cool._ i think there might be some truth to the idea that some old tubes sound better than new-manufacture, although i think that probably has to do with build quality and QC (i'm sure some of the new tubes are cheap for a reason.) don't get me wrong, i love digital stuff and i'm a gadget nerd. but whether the tubes work or not, i find something really artistic about them and i could stare at them for hours. there's quite an aesthetic appeal to them!
The power transformer puts out several voltages (see my video on Power Transformers). One of them is the high voltage, usually around 400V, that is applied to the plates of the output tubes (and other tubes, but at lower levels). Before it is applied to the plates, it has to be rectified into positive Direct Current, or else it would cause a loud 60 Hz hum. This rectified, positive DC high voltage is called the B+ voltage, by old timers (like me), because in early, battery-powered radios, the high voltage came from the "B" battery (there were two other batteries, the A and the C) and you connected the tube plates to the positive terminal of the "B" battery. Thus the DC high voltage to the tube plates was called "B+". We still call it that out of habit, even though the days of battery-powered antique radios are long gone. I hope this makes sense. Thanks for asking a good question.
+Shaman Man No.....if your output "wants" 16 Ohms then you could only connect to one 16 Ohm speaker, two 8 Ohms in series, or four 4 Ohms in series, i.e. the speaker load has to equal 16 ohms.
"So if you're a little under the weather after guzzling about 4 liters of Mad Dog 20/20..." I laughed so loud that I scared my girlfriend and sent the dogs running for shelter beneath the couch. Normally, this sort of thing would have had dire consequences. However, after explaining that I was watching Uncle Doug, she asked, "the guy with the glass of wine and the pets?" This diffused a potentially painful situation for yours truly. I wouldn't have been let off the hook so easily had I reacted in a similar fashion to The Guitologist
Glad you enjoyed it, SND :) We try to throw in a little levity to make the technical parts easier to tolerate. Regards to both of you from all of us in Rusty's Madhouse :)
Nice sound - just enough distortion colour in the sound. I imagine that tone control would be relatively simple to insert, although, of course, this can be taken care of on the guitar.
Ben Morris Thanks, Ben. Actually the amp had very effective bass and treble controls that required no modification. Overall, Newcomb electronic devices are of excellent quality and occasionally available at yard sales for very reasonable prices.
Gosh, you're so right. In my electronics workshop, I'm absolutely tired of this wretched double sided PCB crap. So hard to get components in and out of, hard to test etc. Then some idiot invented a triple layered PCB, so there's tracks inside of the board itself where you can't follow with your eyes! Of course the manufacturers won't give you a schematic of their hunk of junk either.
Amen, Liz. Double-sided boards, whether PCB or eyelet, are a nightmare to test and repair.....especially if they are held in place with wires running from them to the rest of the circuit.
@@UncleDoug I had a tech gut it, leaving me only vol. ctrl and an On/Off switch. Used it to push 2 Weber Blue Pup 10"s, and went to Glass Chime and Jangle heaven. I'd luv to get one of it's big brothers with 4 X EL 84. I think the magic is the 6BR8 and that ultralinear transformer.
That amp is beautiful. What a masterpiece of 1960s electronics engineering. Look at the holes in the chassis around the tubes to dissipate heat, even! This was made by serious people.
Glad you like it, Brad. It really is nicely made and works quite well.
P
I presented this to my friend Jerry @ Kroker Amps. He's been doing this type of design/work for most of his 70 years. He said the ultra linear output transformer is perfect for a low gain acoustic guitar amp, something to consider if you have one of these. He also said, just like Uncle Doug, that with pedals this would work fine with a solid body electric.. The transformer layout is very nice (they are away from each other OT & PT) and it has the 7189 tube option which are the more robust EL84 tubes. Thanks Uncle Doug for your videos!
You're welcome, VR. Ultralinear OPT's are indeed excellent for acoustic guitar use.
That amp really is a work of art and remarkably unmolested given its age. Thanks for taking us along. I will definitely be on the lookout for PA's that can be rebuilt for guitar.
Thanks for joining us, Jon :)
Cheers! Way back in the sixties, me and my musical mates were using radios and the like for guitar amps. We used to just wire the signal up to the top terminal on the first valve! Of course, if you got a radio with an input for the old moving coil 78 players, you were away!
I love the tone of this amp. It would be interesting to hear a "before and after" with that cap mod.
bills48321 You're right, Bill. I will definitely keep that in mind for a future video. Meanwhile you might enjoy the video featuring tone improvement in a Gibson GA35-RVT amp. The change in the Newcomb was similar, but not quite as pronounced.
Great job with this one! This unit looks a lot like a Bogen Challenger PA that I rebuilt years ago into a guitar amp as a teen. It’s fun learning all of the tricks of the trade at that age because they stick in one’s head never to be forgotten. Love your great sense of humor that you inject in these videos.
Thanks, Ronny. Conversions are a great way to start out learning about electrical circuitry.
Years ago,I had an old Bogen PA amp I thought about converting to a guitar amp.Around the same time,I saw a '30s or '40s vintage Bell and Howell Filmosound speaker and cabinet.I could have gotten it for next to nothing.I enjoy your videos.
We're glad you enjoy them, Dan. Thanks for watching and commenting :)
Uncle Doug I got me one! The E40 model with 4 X EL84s! WOOHOOO! It's been recapped with new tubes. With a tube preamp, they REALLY open up. I'll be able to use the 4 ohm tap with 2 Alnico spkrs I've had laying around. Jangle Chime and Glassy Tone for Days.
Wow....Congratulations, Mr. P. It sounds like you hit a sonic home run !! I hope the mighty Newcomb gives you many years of great service.
@@UncleDoug Thank you Sir
You have a good sense
Of figuring out things
Also a master of expression.
Like those chicken
Heads clucking away
On the front.
Yes I saw that movie
2001 space Odyssey
In a drive in theatre
Back in the 70s.
Also saw the sequel
A few years later on TV. I have seen this Newcomb amp video twice thought I would
See it again. Your are a Jewel of a man for amp mods and repair.
Dwight
Thanks so much for your very nice comments, Dwight.
Very well done Uncle Doug. The amp sounds superb and Rusty is quite the gentleman. I just picked up two beautiful Newcomb's. A KX-6a Pre Amp and a KX-25 Amp using two 6L6 outputs. I can't wait to get them restored. Another thumbs-up from me to you.
+TheRudydog1 Thanks so much, Rudy. Rusty and I really appreciate your kind words. Congratulations on the newly acquired Newcombs and best of luck with your restoration of them.
This amp sound amazing! I can tell because if you've got that sound from a camera, i can not imagine how it sounds live! Thanks for sharing :D
+Jonathan Castillo Thanks so much, Jon. The camera microphone really doesn't do justice to any of the amps I record. Some day, I would like to step up to a camera with an input jack for a separate, better quality, microphone.
I don't know but if I were a little under the weather after 4 liters of MD 20-20 I would probably want to cut the power cord off of it, lol. Great sounding amp!
Thanks, Jack. As my old granny used to say, "Everything in moderation."
Well, that's a beautiful piece of equipment you got there. They did a great engineering job.
Another good tip for making a Hi-Fi amp sound more "guitar friendly", is to disconnect both of the screens from their output transformer tap, and make them run directly from the B+ through a resistor.
You could probably hear the Hi-Fi people screaming that it is a heresy while making these changes.
Another great video, always enjoy watching.
I think Rusty is ready for Hollywood.
Thanks, Nixo. I'm glad you share my enthusiasm for the mighty Newcomb E-20. I'll keep your suggestion in mind for future modification. Don't build up Rusty's ego too much, his agent will probably hit me up for a big raise :)
Uncle Doug you have an academic skill that is a delight for the disciplined educated mind with the relaxing touch of Rusty always by your side ... congratulations . e.b.
Thanks so much, EB. Rusty is an essential element in our educational compound.
I just bought one in great condition off fleaBay, with all the tubes. Can't wait to have it checked out by my tech friend. Lots of spread between the power and output transformers. I can't believe it didn't go past $85, good for me. Love the old tube amps even if their design layout can sometimes be wacky, this layout looks pretty decent.
Congratulations on a great acquisition, VR.....and at a very reasonable price. They are wonderful amps. Best of luck with it.
I just got one of these yesterday in brand new, NOS condition.
Congratulations on a fine acquisition, VTA :)
wow..nice score on the Mullards..geez! ....great viddy Uncle Doug
Thanks, Rosie. Glad you liked the video :)
It sounds great, Doug! thanks for the tip about the by-pass capacitor.
You're welcome, Steven. Glad you liked it. Of all the PA conversions I have seen and done, this one was definitely one of the very best.
Yeah, it does look like a Seeburg after that paint with it's nice angles. I used to have a D-80 in 2005.
Hard to believe it's been so long. I'll have to get another one for a hobby soon.
Thanks, JT.
A very interesting project with great sound. The point to point wiring is a work of art.
Thanks, BT. I'm glad there are others who appreciate good, old-fashioned point-to-point wiring. It is indeed an art.....and (unfortunately) rapidly diminishing.
Let's hope we can keep point-to-point circuitry alive, CH.
Hahaha!!!! Mad Dog 20/20. I haven't even SEEN a bottle of that stuff since I was in high school. Hilarious.
Those preset indicators on the knobs are cool as hell! That's actually a really great idea. First time I've ever seen that.
Mad Dog, Ripple, and Country Club Malt Liquor were standard refreshments at all social gatherings back in the old days.....when "only the best would do" :) On a more sober subject, yes, the presets are very clever.....much better than the indelible ink lines you see scrawled on amps from time to time.
@@UncleDoug - COUNTRY CLUB! LOL! Yep, I remember that too. And Mickey's Big Mouth Malt Liquor. The ladies liked the Boone's Farm and Gallo Spanada.
electronics back in the day are just so kool looking
I agree, AA :)
My puppies ask the same question when my stuff comes through the door. Nice video.
+Wayne Bjorken Thanks, Wayne, and regards to your pups :)
Another awesome amp. Thanks Doug and Rusty!
You're welcome, Sam :)
i just love the sound of a hi fi amp (pa amps in general are hi fi ready) with my guitar amp modeler positioned in front of the input
i have a stromberg carlsen au-58 b from 1955 and omg just plain w/o the modeler is bg and throaty as heck .. as a jazz player i find it wonderful..no additional mods for me tyvm
Sounds like a great set-up, Steve. Thanks for your input.
Uncle Doug I got this one's big brother, the E-40 model modded with guitar input and spkr out jacks. HUMs w/out anything plugged in. Turning up the Bass ctrl, the HUM is horrible. Seller paid to ship it back and have his tech look at it. That tech can't handle the problem, so seller is paying to ship it to a tube amp tech we both know and respect. I look forward to giving a happy update soon.
Depending on the frequency of the hum, it may or may not be a tough one to repair, Mr. P. Good luck with it.
@@UncleDoug FIXED! WOOHOOO! Using a tube preamp/compressor it works great plugged into the Aux input. Thanks for inspiring me to get back into TUBE Heaven.
@@MrPiperian Congratulations on a successful solution to your problem. Best of luck.
Garard, yes Sir! Later went bigtime with Techniques.... I wish I could have heard the tone b4 and after. But the after sounds pretty nice!! I remember Bogan PAs...Nice
Thanks, Wayne.
I love these amp shows ... Absolutely Brilliant Uncle Doug ... Hopefully I can meet you some time on my trip to texas where my cousin lives ... That would be sooo sooo cool ... Another Professionally explained video And valued information ... ))) ... Say Hey to Rusty And kitty for me ... ))) ... P.S. great humor ... lol
Thanks so much, TA :)
This amp sounds great.
Who needs distortion or effekt (pedals) when you have a so clean reproduktion Nice for a change to hear how clean a guitar can sound.
Thanks, Mikael......glad you liked it :)
@@UncleDougYou know, I still have my Newcomb D-10 that I need to recap and make into an instrument amp.
That
i have both guitars and basses and would love to be able to use it with both.
I'm thinking that clean, hi fi tone would give some sweet, clean tones for a bass.
Great video and nice to see Rusty! God bless
Thanks, Peter. Our best to you :)
very cool. my neighbor gave me his dad's old newcomb e 10 amp. it has the same phono input as yours, and a square four contact mic input. a similar speaker setup with the ohm choices, although i think you just pin the speaker connections to that round selector socket. one of these days i will have to see if i can convert it to a little guitar amp head.
Good luck with it, LK. They make a really nice guitar amp.
These are used at square dances! They LOVE mid-range speakers for some reason! One of the models of speakers that are popular are called '"Yak Stacks" - several small midrange drivers in a column .
I guess if it's a square dance where someone is calling out the steps, midrange would suit vocal clarity.
Thank you Doug for another very cool video! Someone said it right, Rusty really is the cherry on these lovely tube sundaes! Keep 'em coming, I am learning a lot.
You're welcome, Roger. Rusty and I are glad you enjoyed the "sundae" :)
Uncle Doug Check me on this, but the Newcomb uses a split load phase inverter, right? See, I learned something....
Yes, indeed, Roger. Looking at the schematic of the E-20, the top center tube is the Phase Inverter. Its plate drives the grid of the upper output tube, while its cathode (opposite phase) drives the grid of the lower output tube. It's also known as a Cathodyne Phase Inverter. Good call !!
Now for a second test, take a look at the Newcomb Model G-12 schematic (either in my video on this model or download it on the Internet). Same manufacturer, but what type of P.I. does it use? Warning: It's a little tricky.
Uncle Doug I think it's a paraphase, because it splits the signal coming off the 6SF5 tube plate and sends it: 1. to the first power tube, and 2. to the 2nd 1/2 of the 6SC7 preamp tube's grid and then connects that plate to the 2nd power tube. And there's a resistor going to ground just before the signal hits the V1 grid, to bring the signal down in balance w/ the other signal. The 6SF5 has only one triode, so it couldn't be used to do both sides of the phase inversion; but the other 1/2 of the 6SC7 was available. I suppose one could connect the 6SF5's cathode to the cathode of the 6SC7 and get a long-tailed pair PI?
Roger Taylor I read up on the 6SF5 here: vinylsavor.blogspot.com/2013/04/tube-of-month-6sf5.html
Hit that front end with a clean boost and it'll overdrive ok. Nice work Doug- I have two of the e-10 Pathfinders and owned the e-25 for a while.
I believe you, KT. Thanks so much for the nice comment and input.
Another Fantastic video Uncle Doug - Bravo - greetings from Brazil :)
Greetings, Mudy, and a big hello to all the viewers in Brazil. Rusty and I are glad to hear that you liked the video. Thanks for watching !!! :) ^. .^
Uncle Doug Always a pleasure, i quite enjoy your sense of humor as well - + really like it when you go thru the schematics Cheers
mudylafeet
Thanks again, Mudy. I hope Rusty and I can keep you laughing, and that the tech discussions continue to make schematics easier to understand. :)
I wish u wer my uncle. Great job!
Me too, V. I like your kitty pic......it looks just like Jacky.
Nice amp and not too bad guitar playing either....I liked it.
+PeterDad60 Thanks, PD....glad you liked the video :)
I probably also would have liked the "sickly pea green" you painted over, but I love the color, and it looks like it would be the original color. I didn't know there was color matched spraypaint for Seeburg jukeboxes, but I've got to get my hands on something like that- there just aren't enough good rich colors in newer paint it seems. I used to own an AMI D-80 juke that I restored. Seems that Seeburgs are the best jukebox, I'd like to own one someday.
+Joel Thomas Thanks, Joel.....glad you liked it. I bought the spray paint many years ago (and it still works !!) when I was restoring vintage jukeboxes as a full-time business. Back then, all sorts of original and good reproduction parts were readily available. Now, due to the decline in enthusiasm for old jukeboxes, the availability of parts has dwindled.
@9:00 where the red caps are in place, mine has components there. They look like capacitors, but according to the labeling on the chassis, I’m assuming they are transformers.
Very strange, Vince. I have never seen an E-20 with any components plugged into those sockets.
I checked it out again, and yep, they’re transformers . It shows a pin out and part number on them too. I can PM a picture if you like.
Just searched via google “tr-91 Newcomb”. You can see and image of one there as well.
I did the search and you're right, they are input transformers for microphones. I guess they alter the impedance of the circuit to suit a microphone. They also seem to be rather valuable......so you are a lucky guy.
Uncle Doug, if it does not affect guitar output in a good way, I may keep them unplugged for now. I will try both ways once I put in the 50mfd 100 volt cap that you have added as well.
Let us know what you discover, Vince.
I actually use a ‘62 and ‘67 12” Oxford speaker out of a Thomas organ and they’re absolutely magnificent mated to my Vox ac30. Also, historically, Thomas put oxfords into the very early vox ac30s, as licensed from Vox.
I'll bet it does sound great, Dan :)
Those would have an even wider range of frequency reproduction capability than guitar amp speakers (at least theoretically -- more octaves). More likely, such speakers would do fine in either instrument amp. It's the voice speakers that are so disappointing.
mogen david reference at 6:40 - and then yes I got woozy with what followed
Greetings, Andrew. Fine tubes......like fine wine.....always intoxicating :))
Another good video ! Good job !
Thanks, Kal. I'm glad you enjoyed the video. I thought Rusty really outdid himself on it :) ^. .^
Nice coversion and nice sounding amp!
Thanks, CG :)
You're welcome Uncle Doug.
That makes a sweet head for a mini stack
Yes, it would.
What a wonderful channel! I HAD to subscribe.
Anybody who uses the word "snazzy" is definitely from my generation.
Thank you for all the wonderful videos that will surely keep me occupied in my Denture Cream years.
Cheers!
Wow.....thanks so much, Duke. Welcome aboard !! I was a teacher for many years and would (from habit) use old phrases like "snazzy", "what a drag", "I'm hip", etc. during classroom discussions. The kids loved it. I would hear them later using these terms on the playground. Good expressions never die, they just skip a generation :)
Uncle Doug Thanks for the reply.
I just watched your 12 amp comparison video.
They were all "snazzy" but the Kustom was downright "boss".
Wish I still had mine! It's sad they were "frowned upon " back in the day.
I guess because they're transistorized rather than tube, some people looked down on Kustom amps, but quite a few famous musicians used them on stage. I just love their looks.....completely unique (and "far out") :)
So true. Back in the day they weren't "vogue". You were so "uncool" if you had one.
Oh my! I remember this amp!
Walter Stahl I hope your recollections are good ones, Walter :)
I love how Rusty requires your sense of humor to be set to "eleven" at all times! Most informative as well. Thanks Rusty for keeping him on his toes! However, instead of valium, perhaps you recommend a quaalude next time?
Rusty has always kept me on my toes......and occasionally other parts of my body, when I trip over him as he naps in the workshop :)
Uncle Doug,
There is an amp that has been in my dad's attic for as long as I can remember. With it, is a metal plate with oiling instructions and indicates it is a Hammond model M amplifier, serial number 11836, 115 volts AC, 60 cycles, 93 console watts. There is one larger transformer that has no corrosion, as well as a smaller one, also without corrosion, that has AO-20936-0. The tubes look okay, and are as follows: 5U4, 6BA6, 6V6, 6V6, 6SC7, 6J7, 6J5, & 6SJ7. On the "front" are various screws, that look like wires have been attached, as well as a couple of what looks like RCA inputs. The best I could read with my old man eyes: "Pedal Cutoff" "Key SW" "Decay SW" "Sus SW" "Pedal In" "Voice Coil" "Ped" "Att-Key" "VIB"(?) The RCA looking inputs have (best I can tell) "Radio Phono" & "Spec Input"
So……would this make a good guitar amplifier? I know absolutely nothing about electronics, but do play guitar, and love the different colors and temperatures of tones that tubes can produce. I am not asking how to do what needs to be done, because I am sure I will be finding someone to be with me every step I take…..I've just not seen anything other than amplifiers from M3's, M2's, or M100's anywhere. I DID, however, find the schematics, block diagrams, wiring for the organ itself….but what is the amp called? AO-20936-0???
Thanks, and sorry for asking so much !
Ke & Ri
Love your commentary.
Thanks, GS :)
sweet vintage tone....fendery
Greetings and thanks, Flip. I agree, the tone is indeed "Fendery". These E-Series Newcomb PA Amps make excellent guitar amps....and at a bargain price.
I guess you wouldn't want to mess with it too much, but it might be interesting to have a 3PDT switch to wire the output tubes connected to the plate supply for pentode operation, the UL screen tap, or tp the plates themselves for triode operation. Or put a switch to put the input triodes in series.
I've never felt that the benefitof such multi-purpose wiring was worth the effort, Bubby. If you set up such a circuit, let us know how it turns out.
Very nice .love what ya did with the conversion.Good tone man .Susie Q?
Thanks, Stephen. Close. It was my amateurish rendition of Green River :)
any tube amp is a hidden gem as long as the xformer are there
Indeed. They are getting a little pricey lately.
Super cool dude
+joohop Thanks :)
Unca-Doug has hit the vintage market jackpot again. I could spend days messing around with various effect pedals with this jewel of an amp but I'm curious as to the original PA duals. . . it looked like there was room enough in the two cabinets to wire up a higher frequency tweeter in each. Have you considered this? I'd love to hear it if you do. There appears to be plenty of power to drive that configuration. Thanks for posting an excellent presentation!
Greetings, CB. Your idea of adding tweeters is an interesting one, but the main deficiency with these speakers is bass.....there isn't much at all. The tone of the original speakers reminds of the piped in "music" at McDonald's or the (endless) paging at Home Depot. Being old fashioned, I tend to like a lot of warmth and bass in my guitar tone, and the only way I could get it was to shift to a more guitar-oriented speaker. I really appreciate your time, interest, and input. Thanks so much !!
Uncle Doug Just curious - is the frequency response of the speakers low end capability more a function of the circuit elements as they're configured or the speakers themselves? Granted they are old, but I can't help but think that 12" ceramics of this quality can't handle a little bottom? I'm not talking that windstorm generated 6 inches off the floor bass which causes building foundations to decay. . . perhaps as an acoustic-electric guitar rig or, dare I suggest, violin?
TheCarablanco
A good question, CB. I think it's the speakers themselves. I really tried to use the original speakers, but they simply can't cope with the bass frequencies that a guitar generates. The ceramic magnets are rather small and the cones suspension is a little flimsy. They tend to flap around and sound pretty bad, even at moderate volume. I think the proof of this is that when the same circuit is connected to a large-magnet, firmly suspended 12" guitar speaker.....it sounds great.
awesome doug! i picked up a bogen challenger cha-20 pa amp at a yard sale for 50 bucks a while back. i did similar modifications to turn it into a guitar amp (including adding a bias cap) and it sounded great! I wasn't so lucky with my tubes though. all tubes but the 6v6's on my amp were shot and so were the electrolytics. cant wait for more videos!
Greetings, Tom. I've never owned a Bogen amp, but I understand they are of very good quality. Sorry about the bad tubes, but for $50, you still hit a major home run :)
Uncle Doug, I always read how the location and treatment of filament wires is crucial to lessen hum, but anytime I see a point-to-point amp (vs. turret/eyelet board), the filaments are usually not twisted, they run near the pots, etc. So, how do point-to-point amps get away with that? Tricks like DC elevation? Or is it really not as big a deal as people make it sound?
tgitarezam b I believe that in any well-built amp circuit, all AC wire pairs should be twisted to reduce hum, TG. Perhaps some builders skip these details, but like any complex undertaking, there is only one way to do it right.
Chicken heads look good. Early PA and school dance record player amplifier.
I remember dancing in the school gym to a some kind of special occasion decoration theme and hearing Santo and Johnny's Sleepwalk coming out on each side of the the stage with these kinds of PA setups...those were the "HAPPY DAYS" with
"The Fonz and Richie" ..and of course there was the "Our Miss Brooks" show where she would announce the school day's events over the school PA system.
Years later I did use that 25volt secondary o/p tap (that you mention) for those older shopping centre central walkways to drive several 8 inch ceiling speakers..You could drive quite a few speakers with this method as long as each speaker had it's own individual step down transformer. Was that a few strains of "Wipeout"?
SuperCarver2011 Thanks, SC. If you're speaking of the final two tunes, they were similar versions of something I made up, with a little flamenco flair. Rusty helped me compose it :)
Uncle Doug Your trusty K-9 sidekick is very talented. However, I presume he doesn't sing along when you
play those "Dog-gone blues"..LoL. I get a kick out of seeing the look he gives you when you ask him for
any assistance.
Rusty is an excellent musician, assistant, and source of inspiration......but may seem reluctant to pitch in with the menial tasks. It's just his "video persona". In real life, he is a tireless worker ;)
Uncle Doug Lol! You and Rusty are "killing" me.
Nice video Uncle Doug, but what about that "Natty Co" speaker? It sounded really good. I'd call that paint color "Surf Tone" :)
Thanks, CA. I found that old Natco movie projector/PA speaker in a local pawn shop and have been using it as my shop speaker for many years.
@11:11 , you mention the ultra-linear xformer is wired to the power tubes to reduce distortion. If another 12ax7 and some resistors and capacitors in the right places, can the rick-tone tremo-drive be added to “force” distortion and add tremolo as well? Asking because I recently obtained an identical e-20 from a friend, and may want to take that extra step.
Edit- I just thought of something. Since the 12ax7 is used on the two separate channels, maybe I would only modify the one side with a lower plate voltage to make distortion, feed the modded channel into the other, and maybe add a 6AU6 or something similar for tremolo instead. Not sure how I’m going to do this yet. We will see though.
one more edit- reading through the comments state other ways to bypass the ultra-linear with resistors. I will be checking some Mesa-bogie schematics where it has switchable ultra-linear lines. Still may add tremolo.
The RickTone Tremo Boost can easily overdrive an amplifier into saturation. You don't need to add anything to the circuit. It can also create a Tremolo effect at the same time, if you wish.
One of your older videos that I missed somehow (I used to sign in with my company account, eRyde). Cool video Doug. Two things I noticed on the schematic. The voltage for the 6BQ5 at the plate was 360 (if I read it correctly) which is pretty high for an EL84 which has a max rating of 300v in my books (Sylvania and RCA tube manuals). Also the screen voltage is slightly higher than the plate voltage, albeit only 3 volts (again if I read it correctly). So now I'm curious as to how far you can actually push an EL84 and still maintain a decent tube life of say at least a year before it starts to degrade.
I have read the low max-PV values for 6BQ5's and 6V6's in the tube manuals and am puzzled by them, since both tubes routinely operate at much higher plate voltages than the manuals would suggest. Indeed, Fender ran the 6V6's in their BF and SF amps at well over 400V. I would suggest that PV does not determine tube life, but rather it is Plate Dissipation that is the most important criteria. As long as you keep the PD below the max for any output tube, it's useful life should not be reduced.
I just ended picking up a Multi Kord Model 125 single ended amp which appears to be from the 50's maybe? Looks to be in very nice original condition except the speaker cone is shot. Appears to have original everything else in nice shape. I actually picked this up with you in mind and would like to give it to you for all the help and kind assistance you provide to everyone in your channel. I'm an old car dog like you and have restored a lot of cars (that's why I knew so much about the 70 Mustang Boss 9). In any case, this amp seemed like the kind of thing you like and it would be my pleasure to send it to you to do with as you wish. Bert
Thanks so much, Bert. If this is purely a tube amp (no semi-conductors at all) with a power transformer (not series-filament) we would love to receive it and possibly use it for a video. Please provide your e-mail address and I will contact you directly.
@@UncleDoug I've tried to add it here twice, but the message disappears. My guess is they are filtering it out. I've added it to the "about" column on my information. Let me know if you can get it from there.
Yes, I was able to retrieve your e-mail address and will contact you at once.
Wow, what a great find, those Mullard valves are certainly worth a lot on online auction sites. IMO, I think JJ Tesla is just as good in terms of performance although many people would disagree.
As far as UL output stages go, they can be quite good for instrument amps, especially when used with EL84s as opposed to pentode mode (think of the rather jarring jangly overdrive of British Invasion rock, that's the sound of a pair of EL84s in pentode mode). In the UL connection the overdrive characteristic is a lot smoother, much more similar to a triode which gives a more mellow distortion similar to that of guitar amps using beam tetrodes, possibly even smoother. Distortion is also lower when not overdriven, producing a cleaner sound. It's all subjective anyway!
You might want to watch out for that cathodyne phase inverter, they can behave a little oddly if you drive them hard.
+Michael Fearnley Very interesting. Thanks for the input, Michael.
My pleasure. I would recommend putting the PI into see saw operation instead of cathodyne for best overdrive performance, doing this gets rid of the grating anode voltage spikes on the cathodyne configuration (which will mess up the smooth OD of the UL configuration) as the cathode load goes into positive bias and conducts.
You also get the benefit of reducing the cathode to heater voltage, reducing hum and improving valve life.
Just wondering what speaker was used in the demo portion. I have a Jensen P12Q that I thought, from your description, would fit in perfectly. The sound you got as the end result was pretty close to what I had in mind.
Another beautiful video UD. Thanks!
You're welcome, V. You have a good ear. I was using a 1950's 12" Alnico (probably Rola) speaker, which does sound much like an early (tweed-style) Jensen. If I were to build this chassis into a combo amp or build a cab for it, the P12Q would be at the top of my list for speakers. Thanks for your input !! :)
Uncle Doug A huge YES! to the Rola speakers. I have a small collection. A very nice alternative to the Jensen's, at least in in Hammond's mind, as these were used as an alternate, and definitely not inferior speaker in their organs. The 8" Hammond Reverb Rola speakers are among my favorites. I'm looking to build a mini 4X8" cab with these. Ooooops, maybe I said too much :(
Hey Uncle Doug & Rusty, Very nice amp, will keep a look out. I was going for my blood pressure med's when I heard what the tubes were. I saw your light bulb current limiter hiding behind the amp, cool. I made one per your video, tested, works great. As always a fun and educational video. Pretty good on the guitar. Look up D'C'G trick on YT. Take Care,C.
+Cass Virgillo Thanks, Cass. I had to visit Walgreens too, but it was for some Depenz, rather than BP meds :)) Glad you enjoyed the concert and the lurking Current Limiter. Happy Holidays !!
I would love to be able to repair and modify my tube amps.. I'd also love to be able to scratch build a quartet of small Fender Champ based amplifiers for home use , linking them using a computer with my favorite amp sims and vst effects within my Sonar X3 D.A.W. which will recognize multiple interfaces simultaneously using ASIO drivers..This way i can play backing tracks within the DAW through their own interface and have the amps on two over interfaces in sync with the backing track and have as many effects changes as my heart desires with automation writing so i can just sit back and play and not have to push anything at any time..With the automation it is like having a complicated sequencer doing all the work without being complicated
I'm relieved, TM.....I was worried that you might describe something complicated and hard to understand ;)
@@UncleDoug
Lol the way i describe things is convoluted .I could describe making buttered toast and half the people reading it would swear i somehow connected it to the signing of the " magna carta " lol..I don't have your gift of uncluttering an explanation !
@@toobmaniac Thanks, TM. It comes from years as a math and science teacher.
I wonder why you don't see those air holes around the tubes and transformers in combination with the louvres on the bottom in guitar amps.
Seems like a good way to keep exces heat under control... you'd expect to see that on small box head amplifiers but i've never seen that.
It shouldn't cause interference now should it? Is it just the added labour why guitar amps don't have these?
It does seem like a wise engineering modification, Fra, but since heat rises, one could question the benefits of holes around the tubes. The main source of heat is above the chassis surface, not within it. I can see no reason why it would reduce the shielding of the circuit.
@@UncleDoug Thanks for answering.
Depending on the amp chassis i think it might because of the laws of thermodynamics.
A Fender style amplifier (or other brand) with the amp chassis in the top of the cabinet wouldn't benefit much i'd imagine as it would actually allow heat into the chassis but i think a bottom loaded Marshall style head actually would.
Those regularly have a screen in the back or top of the head cabinet for the heat of the tubes to escape trough but no real way of sucking in cool air.
The rising heat escaping trough the top/back would create a vacuum sucking fresh, cool air in trough the bottom louvre/screen and trough holes around the tubes in the chassis.
I might be overthinking this and overestimating the added benefit but it does seem like a good way to cool the capacitors and tubes somewhat in small box head amps.
I thought a lot about this subject because i hope to one day build a 5f2a based Princeton style circuit but in a Marshall head style chassis and cabinet as small as possible...
About the size of, or, a little wider than a normal sized amp handle and was planning on using vents and holes because with a P.T, OT., choke and tubes producing heat in such a small housing i figured i could use as much cooling as possible....
If it ever happens that is..., i'm better at planning and thinking about building things than actually doing it i guess... but i digress and waisted enough of your time you could be spending on making these awesome videos already.
Thanks for listening to me rant and have a good day.... give my regards to Rusty and Jack.
No problem, FraJa. Your rants are always welcome here :)
Uncle Doug is it that 6BR8 preamp tube coupled with that nice UltraLinear output xformer that makes this amp's sound so unique?!? For guitar it's SO 'glassy'...dunno another word for it. I can't help but think this wouldn't be too hard for me to build after seeing the underside. I had one once, had a tech rip out the tone circuit and that amp had jangle and chime for not days, but YEARS. " I MISS IT" is an understatement.
I would assume that the unusual pre-amp tube plus the UL OPT definitely contribute to the unique tone, Mr. P. It shouldn't be too hard to clone.
An Accessible Fuse Holder Would Be Good.
My MPA 90 From Radio Shack Was
A P.A System & I Played Guitar Over
The Original P.A Speaker.
Yes, it would.
Bom dia Mestre muito legal Sul do Brasil
Would it make sense to connect the two preamps in series, reducing the number of inputs to one, and so utilizing all available gain stages for more distortion?
Each of the preamps is set up to accept a low voltage (i.e. less than 1V) input. If you placed them in series, the second preamp would receive a signal of much higher voltage than it was designed to accept. This would result in all sorts of distortion, as you suggest,.....but none of it would be of the "good" type.
any special advice on the heater wires when constructing an amp point to point? I notice they are not twisted together in this amp, and noise is not a problem. I have gathered all of the parts to construct DaGeezer's "Little Wing" mini-Bassman that uses 6BM8s. The chassis I want to use is a bit too small for a turret board, so I'd like to do point to point, but I'm worried about noise. Thanks!
Greetings, Jim. It's always best to tightly twist the AC wires to the tube heaters, and when you get to the tube, don't wrap around the perimeter of the tube base, but arch up, over, and straight down to the pins to which you are soldering. Good luck with your project :)
Were those little 'reminder' pointers on the controls original to the unit?
Yes, they were already there when I got it.
Wow this this is neat!
+Jonathan Kosyjana Thanks, Jon....glad you liked it :)
ohh yeahh way cool,your channel kills it! thanks for your videos, i've already learned alot!keep it up =]..you dog is awesome by the way
You're welcome, Jon. Rusty and I appreciate your kind words and wish you the best :)
uncle doug, this kind of work fascinates me, but I'm afraid the few videos I've watched haven't turned me into an experienced and knowledgeable tech. where can I go to learn the most basic principals of these circuits and then work my way up to making my newest uncle proud?
+James King Rusty and I have posted 121 videos so far, James, and a bunch of them discuss all aspects of tube amp circuits....how they function and are designed, built, tested, etc. as well as all sorts of safety tips. I suggest that you watch some of them and see if they are helpful. Good luck :)
Anybody out there who's got an original Vox AC-15 is drooling over those tubes.
I must agree that they are definitely drool-worthy tubes :) I would hate to see the total bill if you had to buy them from a premium tube supplier.
Do you know if there's any truth to the rumors about people like Aspen Pittman going to Russia and China and getting them to upgrade their designs and literally reverse engineer the old American and European tubes? I've been told that the new Mullards and Tung-Sols are very good re-issues, but I haven't tried any of them yet.
I have not heard these rumors, but from experience, I feel that many of the newly manufactured tubes are of excellent quality, often with superior power handling capability (higher plate voltage and current) when compared to vintage tubes. Some of the early "replica" tubes (i.e. from 10 to 20 years ago) were not so hot, but I think they're getting better and better at meeting and exceeding vintage specs. This is probably due to the huge, renewed interest in tube amplifiers and the large amounts of money being spent on them (and tubes).
I havealot of those 5y3 tubes idk if i ever tested them i have so many but used to sell tubes but now as nos tubes are getting scarce and expensive i wont be selling tubes on ebay anymore ,i only did for a few months but kinda wish i hadnt sold the 1s i did sell oh well such is life
You can't keep everything, Joe, no matter how hard we try :)
Hi Uncle Doug. Thanks for this video. I've recently acquired the E-40 version of this amp in the same beautiful mint condition. It has the 4x EL84/6BQ5 output stage. I was wondering if it matters which of the four output tubes I should pull for a reduction in output volume. Does it matter?
I intend to copy your cathode bypass mod and use this amp to power a 2x 12" blackface era Fender cab that I picked up on CL. Are there any other pointers you can give for the E-40 model?
Greetings, Slog. Congratulations on acquiring a great amp. I am completely impressed by every product I've encountered from Newcomb.....the amps are beautifully constructed and sound great. Here is an excellent site to explain the process of output tube removal: www.premierguitar.com/articles/20713-ask-amp-man-removing-output-tubes-to-reduce-power I think you will like the cathode bypass modification. I have no personal experience with the E-40 model, and really have no other modification suggestions, simply because other than sounding a bit sterile (which is improved by the CB cap) the amps have wonderful tone as-is. Best of luck with your new amp !!!
Nice amp, what would be the characteristics of a "guitar friendly" speaker? Thanks, Sorin
Greetings, Sorin. A "guitar friendly" speaker would have a larger magnet, a larger diameter voice coil, and a firmer suspension around the perimeter of the speaker cone, to better cope with the bass frequencies that a guitar produces. This is especially important in open-back cabinets (such as these) where there is no trapped air to moderate the excursion of the speaker cone.
Hi Uncle Doug, curious if you have any interest in converting another Newcomb pathfinder E20 to a guitar amp? i recently found this collecting dust in a shop locally and took it home.
Hopefully, with the help of my, and other, videos, you can do the conversion yourself, MJJ. Give it a try and see :)
Seeburg juke amps? I've got a Seeburg MA1-L6 amp which has been converted to a bass/guitar amp. It took me almost two years to locate a low-res and nearly useless schematic for the L6.
Greetings, Scott. As I recall from my jukebox days, the MA1-L6 amp was used in the Seeburg "Trashcan" amps from the late 1940's. There was a later HFMA1-L6 (High Fidelity) amp used in the 1950's 100-R, C, J, etc. models. I found the following schematic, which seemed rather legible: www.4tubes.com/SCHEMATICS/Music-amps/Seeburg/ma1-l6.jpg
Could the negative feedback loop have a simple switch to defeat it or should there be something else in circuit to accomplish this and (as per my usual) what did it sound like before adding the bypass cap and possibly a switch for that as well... (his eyes widen as he screams "more bells, more whistles!!")
Thanx for another gem, Uncle Doug and cheers
You're better off using a pot and making the NFB loop adjustable, Jonny. You're welcome :)
All the tube amp stuff I get never seems to have a schematic, thought I'd ask if you have a good source for schematics. thanks
Virtually all the schematics I use in the shop and in videos are simply downloaded from the Internet. A Google Search can turn up the schematic to just about any amp ever made. Give it a try.
hello...i have a Magnovox Playfellow amp that has been partially converted to guitar...i will send you a copy of the SAMS...it has a 1/4" input into the volume control, and I disconnected the NFB loop...can you please give some some guidance for bypassing the biasing resistor, as you did in the Newcombe??..thanks!
clearview02 it's SAMS 249-9, if you have access to it...
clearview02 You can use alligator clips to (carefully) test different value bypass caps, in parallel with existing bias resistors in the pre-amp and output tube(s). I usually start with 25uf @ 50V and see if I can hear improved tone and volume. It's a trial and error procedure, using different cap values in different locations, until you come up with a tone that you like.....generally warmer, with improved bass and gain.
Uncle Doug Thanks for your suggestion and many informative videos...i went back and watched your video on cathode bypass capacitors again--a lot of material there!...i did much the same experimentation on a PCB amp that had intermittent signal issues...disabling both the effects loop and footswitch circuits took care of the intermittent issues...i was surprised how much the signal "opened up" after disconnecting the effects loop...all those extra capacitors and resistors took a lot of "fizz" out of the sound...after that mod, i experimented with different value capacitors, to get a tone i like...but i didn't use the alligator clips, so i got lots of practice with my soldering skills!..i read somewhere that a lot of Fender's classic amp circuits from the 1950s came about from pure experimentation; as Leo was an accountant, not an electronics engineer, by prior training and vocation......
clearview02 p.s. and i wonder how much effect the mid-range driver has if you tweak the other elements as needed??...i know that Peavey used to put mid-range drivers in their tube guitar amps...Chip
Somebody is pulling your leg about Leo Fender, Chip. He was a highly experienced radio repairman and electronics whiz, who personally developed the guitars and amplifiers that made his name and company famous. In fact, he was so focused on the technical side of his company that he often neglected sales and accounting.
Re the mid-range driver, most guitar amp tone circuits tend to scoop out the mid-range, because guitar pickups tend to emphasize this portion of the audio spectrum. Since we virtually never see popular guitar amps with mid-range speakers, I would tend to think they are not much of an asset.
It looks a bit like a jukebox amp.
Personally i would have it restored and left it as it was originally. But that´s my opinion ;) Good work anyway and have fun with it!
Thanx for sharing!
It does have a "jukebox-amp look", TC. At least the modifications were rather superficial and easily reversed. Thanks for your input :)
*****
Thanks, Roger. I think I'll use it as a head. I have some good speakers in cabinets that work well with it. The original speaker cabs are open-backed (no bass resonance) and rather cumbersome, especially if good (heavy) guitar speakers were installed.
I think this unit was intended to be used for speech amplification at sports or at a faire.
Therefore there is no need for any bass responce. Open baffle makes the unit more lightweight thus easier to carry the whole thing around. The cones of the speakers are special designed for it. You can see this by looking at the very small ferite magnet as well. It´s intended to be used only in (lo)mid to high frequency range. But with a very good efficency, well over 100dB SPL at 1W/1mtr. is typical for these speakers.
If you mount a guitar speaker into this sort of cabinet it will sound awful and you´ll may end up with a blown/damaged speaker due to too much cone excursion at low end frequencies.
Use only the Amp like a Head is the best thing you can do.
But some Harp players will love this thing with its original speakers, because this is exactly what they are looking for. This old PA units match exactly their needs in terms of frequency response and overall sound feeling...
Thanks for the excellent and informative input, TC. Your recommendations coincide quite well with my planned use for the unit. I was, however, unaware that the tone response of this system was so suitable for harmonica use. I'll keep that in mind when seeking a new owner for it. Thanks again for your time and assistance :)
Thanks for the great video Uncle Doug! I just picked up a Newcomb M-12 55W PA amp, and am hoping to convert it to a guitar amp. It has an RCA cord that I believe is an input, but it’s the same on both ends. Can I buy a RCA-to-1/4” cord (such as at Radio Shack) and play as is, or should I convert the input? Also, I don’t know almost anything about transistors, or whether I’d need the bypass like you added for tone? Sorry about so many questions, learning a lot really fast, haha. Any info appreciated, thanks :)
You're welcome, Donny. I really can't answer all your questions without evaluating the circuit.....so I think you would be better off trying the changes you mentioned, seeing if they work, and modifying them if they don't. This is, by far, the best way to learn.
Btw, Would you mind sharing the circuit schematics? (like a link of the photo)
+Jonathan Castillo I have no way to host such a photo, Jon. Perhaps you take a photo of the screen at 9:20 ? I have tried this is the past and it generally works fairly well.
That Would Make A Good Portable Pedalsteel Guitar Amp
I'll bet it would, Roger.
I replace those hidden fuses with a inline screw type AFTER I replace the pwr cord with a 3 prong
Thanks for your input, Lost.
ooooh those tubes!!!
Greetings, Cat. I'm glad someone out there shares my slobbering enthusiasm for high quality, original, vintage tubes. More and more often, I am encountering modern replacements instead of original old RCA's, G.E.'s, etc. You could probably debate all day over whether there is really that much tonal difference between old and new......I tend to think there really is a (sometimes subtle) difference.....but finding original tubes in an amp always impresses me as strong evidence that the amp was never altered, mistreated, or excessively used. It's like finding a smooth-running, all original, Power Pack 283 under the hood of a '57 Chevy......instead of a crate 350.
Uncle Doug Sorry here but these days are gone. The market for real
*good* NOS USA/JAN/German/UK tubes is about to its final close. Prizes are "through-the-roof" already. As the prizes rise some fellas tear out the Original tubes and smash it on ebay to make fast money, and sell the Amp some two weeks after without tubes to get the max$$$ out of it. For Years a´m looking for a "Jörgensen" all tube organ, its sound generator is made out of 48 ECC83 TFK tubes originally, but all i see is that some units apear on ebay they shorty rise above $1k and up. just because these tubes are in it. the winner tear out the tubes and *dump* the beauty organ *DAMN*
And some NOS telefunken EL34 which I bought recently are not as good as new JJ. So what?
My two cents are: there is a chance to get some good NOS tubes, western made. But i´m entirely out of this by now. As i´m very happy with new made JJ when it comes to standart tubes.
When buying NOS or odd (non standart) tubes i´m always go for formally USSR types. As I found that they are much more rugged/reliable than any other (=similar) types. For instance I use GU50 (ry-50) which is the russian version of the LS50 (EL156). Where one can get the ry-50 for about $5 but the NOS europe is about $100-200 and you´re not knowing if they are really NOS or just claimed like it....
If a ry-50 fails, i *do not care* i just swap it. But with a EL156 i go nuts ;)
But my 4x ry-50 Amps still got the 1st set and its doing just fine.
So i´m replacing all my vintage tubes with russian equivalents. Like 807=g-807 (g-807 is even more rugged than the original US made JAN-807) or EL34 is 6P27C, EL36=6P31C and 6L6=6P3C and EL84=6P14C(-EW which is happy with 400V). Or even use tube with *no* equi like the 6C33C regulator tube.
My daily HiFi Amps are Philips EL6435 (4x PE06/40N output tubes each) which cost a little fortune NOS. But replacing them with G-807 and rebiassing these Amps just work fine and I do not need to wear out the PE06/40N tubes.
A set of 20 (!!) G-807 is equal to *one* NOS PE06 in terms of the prize to pay for ;)
Uncle Doug i'm a sucker for old tubes, mostly just because _they look really cool._ i think there might be some truth to the idea that some old tubes sound better than new-manufacture, although i think that probably has to do with build quality and QC (i'm sure some of the new tubes are cheap for a reason.)
don't get me wrong, i love digital stuff and i'm a gadget nerd. but whether the tubes work or not, i find something really artistic about them and i could stare at them for hours. there's quite an aesthetic appeal to them!
Where are all the filter capacitors ?
Sounds good and clean but like a Vox !
They are in the silver metal cans on the chassis surface, IJS.
I've been perusing your vids for explanation of "b+" power. What is it and why is it so named?
The power transformer puts out several voltages (see my video on Power Transformers). One of them is the high voltage, usually around 400V, that is applied to the plates of the output tubes (and other tubes, but at lower levels).
Before it is applied to the plates, it has to be rectified into positive Direct Current, or else it would cause a loud 60 Hz hum.
This rectified, positive DC high voltage is called the B+ voltage, by old timers (like me), because in early, battery-powered radios, the high voltage came from the "B" battery (there were two other batteries, the A and the C) and you connected the tube plates to the positive terminal of the "B" battery. Thus the DC high voltage to the tube plates was called "B+". We still call it that out of habit, even though the days of battery-powered antique radios are long gone.
I hope this makes sense. Thanks for asking a good question.
I'm not very knowledgeable on electronics, but if I have a 16 ohm out put, can I plug it into 2 16 ohm speakers?
+Shaman Man No.....if your output "wants" 16 Ohms then you could only connect to one 16 Ohm speaker, two 8 Ohms in series, or four 4 Ohms in series, i.e. the speaker load has to equal 16 ohms.
Uncle Doug
Thank you so much for preventing a $200 dollar disaster.
You're welcome, SM. Glad to be helpful :)
Hey Doug That TurquoizYou Painted The Heat Shield is Cool. How Many Watts Is It?
Thanks. Probably around 18W.
@@UncleDoug if I Had An Old Turquoise
Radio I:d Make A Bluetooth Speaker
Out Of It
@@rogertyler3237 I'll bet you would, Roger ;)
I'd pull that ultraliner transformer and get a regular one.
este é o verdadeiro som de guitarra até identifiquei a musica
creedance clearwater revival OK
Sim, foi a minha versão medíocre de uma das suas músicas :)
"So if you're a little under the weather after guzzling about 4 liters of Mad Dog 20/20..." I laughed so loud that I scared my girlfriend and sent the dogs running for shelter beneath the couch. Normally, this sort of thing would have had dire consequences. However, after explaining that I was watching Uncle Doug, she asked, "the guy with the glass of wine and the pets?" This diffused a potentially painful situation for yours truly. I wouldn't have been let off the hook so easily had I reacted in a similar fashion to The Guitologist
Glad you enjoyed it, SND :) We try to throw in a little levity to make the technical parts easier to tolerate. Regards to both of you from all of us in Rusty's Madhouse :)
Nice sound - just enough distortion colour in the sound. I imagine that tone control would be relatively simple to insert, although, of course, this can be taken care of on the guitar.
Ben Morris Thanks, Ben. Actually the amp had very effective bass and treble controls that required no modification. Overall, Newcomb electronic devices are of excellent quality and occasionally available at yard sales for very reasonable prices.
totally Unique~
Glad you like it, Jay.
Gosh, you're so right. In my electronics workshop, I'm absolutely tired of this wretched double sided PCB crap. So hard to get components in and out of, hard to test etc. Then some idiot invented a triple layered PCB, so there's tracks inside of the board itself where you can't follow with your eyes! Of course the manufacturers won't give you a schematic of their hunk of junk either.
Amen, Liz. Double-sided boards, whether PCB or eyelet, are a nightmare to test and repair.....especially if they are held in place with wires running from them to the rest of the circuit.
Another treasure!
+Congi Thu Thanks, Congi :)
I want one.
I'm sorry, Mr. P, but it was sold to a viewer. Maybe you'll get lucky on Ebay.
@@UncleDoug That amp, thru 2 Weber Blue Pups? Clarity, Definition, Chime and Jangle for DAYS!
Indeed, Mr. P. The viewer/buyer of the amp still raves about its excellent tone.
@@UncleDoug I had a tech gut it, leaving me only vol. ctrl and an On/Off switch. Used it to push 2 Weber Blue Pup 10"s, and went to Glass Chime and Jangle heaven. I'd luv to get one of it's big brothers with 4 X EL 84. I think the magic is the 6BR8 and that ultralinear transformer.