Nice work Rusty! Oh yeah, you too Doug... :) The NFB work and Tremolo really helped make it a nice guitar amp. Top shelf work and knowledge as usual Doug. I learn new stuff every time I watch your videos - Thanks!
Thanks so much, I got one of these amps a few years ago, and just picked up a projector speaker cabinet to match. It will be put together to make a kick-ass instrument amp!
Very nice! My former B&H colleague watched part one and found it to be interesting even as he reminded me he was on the mechanical side of engineering. Myself as well during my tenure. All the best!
I've been a HUGE fan of these systems that were used by Bell and Howell. The first thing I noticed was the 25 watt Jensens in the little cabinets! They were the first thing I fell in love with. And I played one forever! Still in the little Bell & Howell cabinet. People would ask me all the time, what was my guitar amp? I would tell them FILMOSOUND... then there were OTHER people using them at gigs. And I began to seek them out. Eventually I got FOUR of those 25 watt jensen loaded cabs and screwed and epoxied them all together and made a FILMOSOUND half stack (a four 12 cabinet) and played that for a long time. The Magnatone I'm playing through at the moment has a late 50s/early 60's filmosound speaker in it, which i think is a Heppner? It's wonderfully bright and differs from the Jensen with an aluminum dust cap and actually superior sensitivity and breakup at higher volumes... certainly the best speakers for guitar I've ever owned started off in Bell and Howell cabs... I have a bid on one of the old 6v6 amps from what appears to be the early 50's or even late 40s... hope i win it! lol
Great project Doug! Really enjoy the conversions. Trash to treasure. Many of your videos helped inspire me to re-purpose a non-functional Epiphone Valve Junior head I had lying around into a hand wired 5F2A Tweed Princeton clone. I learned a ton and now have what has become one of my favorite little tube amps!
Another great video Doug, thanks! Every time I watch one of yours, I get the hankering to clean off the workbench in the garage and finally start that 5E3 project that's been going through my head. I feel that now I'd know what I'm doing, as opposed to just following a recipe and soldering things together without knowing their function. I like how you go from snow to blazing temps there. I was in White Sands a few weeks ago when it was 106 out. "But it's a dry heat" as they say! Thanks again and keep up the good work.
You're welcome, Mark, and thanks so much for the nice comments. We're glad the videos have been helpful. White sands is only about 80 miles away.....and, yes, it may be a "dry heat", but at 106 it's still darned hot !! :)
That is a beautiful Chevy! Love the baby blue with orange flames. Serape is a very cool touch. I look forward to learning more about the Bell & Hell 385. Thanks UD
These videos are so much more informative then the old Mr. Wizard shows I watched as a kid.. that just dated me!! Thanks Uncle Doug!! Not much screen time from Rusty and Jake.... probably to busy inspecting next project..
Thanks for another great retrofit-conversion video. You are an inspiration! I had previously built a clone of the 64 Princeton Reverb and found that the tremolo oscillator was sensitive to component lead length and/ or wire length to the speed pot. You might have a similar issue on this amp. That hot rod is a real beauty! Stan
You're welcome, Stan. You may be right. With the long leads used during my mock-up, it sounded perfect.....dead quiet and great intensity. One I installed everything with the shortest leads possible, some of the properties changed. I will continue to work with it and iron out the small "wrinkles". Thanks for your good advice.
Great "mini series" of a fab re-purposing!! Your work is always amazing, thanks for sharing! I see Jack is forcing his way into the vids......The You Tube fame has definitely gone to his head! That truck is a real work of art!
the clips and hooking stuff up before locking it in is brilliant. this could be done with guitar pickups and other gear before soldering it in. brilliant!
It is brilliant but a word of warning from personal experience. I had several alligator-clip jumper wires just like these and I found to my surprise that over time, the dissimilar metals involved set up a slow corrosion process in between them to the point that the jumpers measured as much as 20K of resistance! I wound up just going at the clip connections with a wire brush, hitting them with liquid flux, and soldering the area where the wires were crimped in with extreme prejudice. That solved the problem.
Hi Uncle Doug, Rusty & Jack, Another awesome conversion by the Master Amp Builder! Not one for a beginner or the meek. I think I will stick to the 5F1 or 5C1 for now, a little more my speed and that aint sayin' much. Lots to learn, but, thanks to you, I think I can. I was waiting patiently for part 2 and well worth it. Glad to see again, you truly are the best. Take care, C.
Thanks, Cass. It was like building a ship in a bottle filled with barbed wire......pretty tough. Rusty, Jack, and I really appreciate your kind comments, however, and are always glad to hear from you.
that was a right tight space to work your magic in Doug. I used to live out west. Love those old cars too. Don't remember rust being much of an issue back then...Anyway, great video about the amp conversion. Lookin forward to your next adventure!.
Thanks, YRU. It was a challenge, like trying to cram 5 lbs. of linguine into an 8 oz. take-home box. You're right about the absence of rust.....it's generally not an issue in local cars. Glad you liked the video :)
Great project Uncle Doug! Again! That tremolo is an absolute winner! By the way, I have an old RCA MI12161 converted to a Fender 5C3 Deluxe amplifier! It sounds similar to this one!
Aphexon: You need to change your privacy settings if you want me to respond to your questions. You're welcome, Aphexon. I always recommend a simple Fender 5E1 or 5F1 Champ as the best first project. Please see my video series where I build one from scrap parts and incorporate some upgrades. Good luck with your project :)
Bulbs are sometimes used as ballast resistors to reduce or limit current in a circuit, such as in the input circuit of some organ amplifiers. They are also used in the photoresistor tremolos found in the larger Fender amps (Deluxe Reverb and above).
Hi Uncle Doug. I'm a little late to this video being I just picked up a B&H Film Projector amp. Do you take customers? I'd like to have this done to mine.
@@deebojones Sorry, Darin, but I no longer do conversions. My purpose in creating and posting videos is to instruct you in doing the job yourself. Best of luck.
Very cool Doug. I will be starting a first time amp conversion myself shortly and I think I will go with the 5F1. I will make a video series from it as well. Have a great day - Regards, Ron
nice Tremolo Uncle Doug! So glad you make these videos. Little by little I'm learning stuff as time permits Today I installed an Ampro deluxe 12 inch speaker from 1957 or 47 to replace an ageing and failing 1946 Jenson in my 1946 Masco Map 15 guitar amp.
Uncle Doug, awesome work as always! Great amp and a lot of useful info as well. Tremolo sounds incredible! I realy love this new "conversion" series. Happy you now have better video quality - looks just perfect. And it seems I have some new materials to work with, huh =) Wish you good luck in future projects!
Fantastic! I think ol "Jim Bob" on the Walton's TV program had some similar rods in his day. Along with "Wally" on "Leave it to Beaver", if I remember correctly. I think "Ward" used the term "Jalopy" back in the day ; ) Back, when all you needed was a summer job, some basic shop tools, a salvage yard nearby and a buddy or two to help out occassionally. Just an fyi, there is a website dedicated to the main cars in the movie "American Graffiti". The deuce had a 327 Chevy in it with some Stromberg's up top. The 55 Chevy was one of three 55's that were built for the movie company and each had 454 BB's in them, as you can "hear" that's no small block Chevy in 1962! I was right about that before I found it years later on the web. Also, the 55 that was supposedly wrecked by Harrison Ford was not. It was a salvage donor car that was a hardtop that they used a 2X4 as a post in the movie to make it look like a 2dr post and if you watch you can see it burning when upside down in the ditch. That's Hollywood! Another one of the 55's was used in the movie "Two Lane Black Top" with James Taylor and Dennis Wilson. I don't recall about the third 55? I'm sure that it's obvious by now that I'm a car nut..
The tremolo sounded fine on the video. Intermittent problem’s are always fun. I really wish you’d have recorded some audio of yourself pulling out those horizontal can caps! They looked really fun as well,lol! Great results tho!
Excellent video - as usual !! I loved your "prototyping" approach - simple - elegant !! And what a great learning process - to put in a pot and audibly listen to the effects of feedback in the circuit. Personally tho - I think after having heard the feedback stifling the life out of the amp - I'd go in an rip it all out. No feedback sounds great !!!
Thanks so much, Donald. Dynamic testing like this is, to me, the easiest and most effective way to optimize tone. I agree that excessive feedback, so often employed in conventional amp circuitry to increase headroom and protect speakers, really smothers the raw power of the amp. Having it be variable definitely makes sense.
Excelente....siempre pensé que no se podían convertir estos aparatos viejos en amplificadores, debido a que dicen que el transformador de salida de guitarra es distinto al de audio. Gran explicación Uncle Doug Saludos
Gracias, Diego. Rusty y yo estamos contentos de que hayan disfrutado el video. Sí, amplificadores de este tipo pueden ser fácilmente convertidos para usar la guitarra. Debe hacerlo por uno mismo. Los mejores deseos para su éxito.
Great modification on the NFB-loop. It's like the amp can breath freely. It has a remarkable sustain characteristic with the root frequencies intertwining smoothly with harmonics and resonances as they fade. Very interesting video about a very remarkable conversion. I'm still puzzled how in the Lone Star State you manage to get snowstorms at 111°F, but that's probably a micro-climate-thing as your videos are too cool for deserts to uphold their temperatures :) Thanks for sharing that!
Thanks, KL. We don't generally get both the 111 degrees and snowstorms at the same time.....Rusty used time lapse photography to make it appear so :) Glad you liked the NFB modification.
I was immediately repelled by the congestion I found in mine, obviously built in layers, with not much thought given to service, but I decided that someday I would probably have time tounsnarl it. I really like how you moved the bias parts and mounted the tremolo on that hum sheild. I sort of imagine that I would find a way to add a reverb tranny to drive a spring off that extra 6V6, but your trem is very cool. My all time favorite trem was the one on my brownface Deluxe.
The best tremolo I have personally encountered is the Vibrato (harmonic tremolo) in a brownface Concert amp. The brownface Fender's were an excellent, but rather briefly offered, series.
I had a pair of them, a brown deluxe in a mahogany cabinet with a D-130 in it, and a brown super in a poplar cabinet with hand cut dovetails and a pair of D-110s but methrats broke into my shop and stole both of them. :( Amazing sounding amps, both of them.
You too, RH. I hope you enjoy the videos. As my old granny used to advise us on the 4th, "Don't hold your firecrackers too long before throwing them" :)
muito obrigado por ensinar muita parte importante sobre amplificadores fui aprender a tocar guitarra em 1968 logo tivemos construir e consertar nossos amplificadores até hoje estou aprendendo muito com o Sr. obrigado amigo por todo material divulgado um abraço Sul do Brasil
The photo electric cell (PEC) from an optical film sound pickup that was the original input to this amp are very bright so it makes sense to have the NFB cranked up to reduce that brittleness.
My "starting point" was the "Lauren" amp at TedWeber. The Schematic and layout are on their site. It was built based on a 50's Princeton. Bigger Xformers, Bigger filter caps, and it was ready to go. I had to wrestle with a high B+, and keeping the screen voltage at 300... Some tweaks were needed to it to get it stable.
Excellent! That tremolo was very strong. Great part 2. If you do a build of a cabinet, you might try different coverings and grill cloth, such as a dark red(burgundy) and a wheat grill. Just a suggestion. I'm sure what ever you choose to do will be good. A head only would be nice also. Less weight and any combination of amp and speaker. Thankz
I need to replace the can capacitors in my filmosound 302 amp and am curious as to where you found those axial capacitor replacements for your 385. In my amp they're mounted on top of the chassis but are still gonna be a pain to replace. Thanks
Nice tremolo sound. I like the "breadboarding" technique, just takes a little more counter space than the "modern" style. :)) Beautiful work as always. Was Jack attempting a Hitchcock type cameo? Nice looking car.
What a nice little amp. Great project Doug. Love that truck. A friend of mine had a 1951 5-window Chevy pickup back in the late 70's 3 speed manual with an LT-1 350. That was a running little truck. A big oak tree dropped a limb on it during a storm. Total bummer. I had a '69 SS 396 4 speed Camaro until I got married. I should have kept the car. Before the Camaro I had a '69 Dodge Dart 340 4 speed. I gave up hot rods for lent (not really). Actually... the section of the brain that says don't got fast to normal people is defective in my brain. Abstinence keeps the insurance rates low :o)
Thanks, Michael. Like you, I've always enjoyed old cars that go fast. My high point, however, was buying a brand new 1965 GTO with Tri-Power and a 4-Speed, that I proceeded to run, literally, into the ground, like the juvenile idiot that I was at the time......but darn, was it fun :) The final indignity came when I traded it in on a new Toyota Corolla 4-Door after I got married and my daughter was born. The trade made sense at the time, but I still wake up late at night in a cold sweat just thinking about it :)
Back in August, 2008 I was blessed to have gone to Gerald Weber's amp camp in Kempner, Texas. I also have his books and videos. He stated that if you have a output tranny that has 8 and 16 ohm taps, your better off using a 16 ohm speaker connected to the 16 ohm tap. He said you will enjoy the full output of the tranny because you are using all of the windings. Please comment. Thanks, Eric
Uncle Doug: Thanks for your videos - I have learned so much from you and them. I am presently converting an old Victor stereo console chassis (complete with original PS) to a guitar preamp platform. It was one of those big old wall units that had been left in a barn. It had a set of EL34 as power tube sockets which I have converted to one EF86 and one 12AX7 sockets for a preamp stage (output to guitar amp input). The other tubes in it were two 6AV6 and two 6BA6 mini tubes. The 6AV6 is very similar to one stage of a 12A. I would like to add a tremolo to the chassis using the 6AV6. Do you think the VibroChamp would work there if I employ one 6AV6 per side of the tremolo circuit you employed here?
You're welcome, James. The VibroChamp tremolo circuit is a good one. I'm not sure about a 6V6 working well as an oscillator tube. You would simply have to try it and see.
@@UncleDoug Hi, thanks. Just making sure your reference to a 6V6 not a 6AV6 was intentional or not? The 6AV6 has a triode configuration that can be used, I believe, like 1/2 of a 12A.
Thanks Uncle Doug. Always a pleasure to watch you work. Didn’t get to hear the amp on full Treble, although I noticed it had been moved from the central position on the very last shot….
Hello, im Facundo from Argentina...I recently adquier 3 speakers and one amp from old image and sound projectors, the amp and one cabinet with the original speaker its a RCA, the speaker its 10" and 8ohms, i think 15w, and the other two speakers are one Jensen with the cabinet from Bell & Howell 12" 16ohms and 15w, and the last dont have cabinet yet but its a Goodmans 60 12" 16ohms and 15watts to...My question is about the wattage of this old amps from the projectors, i cant get the schematics and i am very new in electronics, do you know if this speakers can handle ok with this kind of amps? the 3 are 15watts speakers, i dont want to brake nothing...Well thank u very much!
This is another great job. I'm looking at your suggestions concerning the specifications of the 6SL7. Can the tube be used in a so called single tube push pull circuit? Is there such a thing?
I'm really learning a lot from your videos. I have a Premier-20 16mm projector with an audio amp but the power transformer is bad. Where would you suggest that I pick up a good one for a reasonable price? The only number on the transformer is 18385. The windings are just like the one you have here in this B&H. I would like to remount the components in a custom chassis and replace the capacitors. I also have the Ampro speaker but the cabinet is in bad shape. It may make more sense to build a guitar amp from scratch. I recently retired and I think this would be a good project to take on. Last time I worked on electronics was back in the 80's. Thanks.
Hiya Uncle Doug! I have this same amp and the volume + tone pots on mine are shot. They are noisy/crackly and I would like to replace them (with an added on/off toggle switch). Do you have any suggestions as to what kind of pots I should use for replacements? Thanks for the videos! They’re all great!
Great tremolo sound! I have a couple of 1950s Bush radios which make great guitar amps with a great sound, they have pickup sockets in the back so you just need to make an adaptor and plug straight in, one I picked up recently has quite a hum on it though, quite a few wax caps and I can see at least one is over heating, I'll change the caps and see what happens.
Sorry for two comments in a row! That hotrod Chevy is great. I also love working on those kind of projects. I helped a friend install a fuel injected engine into his 1933 Dodge pickup. We installed a Chevy 350 'tuned port injection' engine with 700R4 transmission.I had to do the ECM wiring and tuning. We got the engine running well, but my friend passed away before the entire project was completed. Here is a picture of the project: 68.209.87.173/33_Dodge/33_Dodge_2.JPG
9:20 U.D. I'd say your methods and techniques are pretty solid. You are working on the same wavelength as Brian Wampler of Wampler Pedals that looks very much like his youtube video on how he breadboards new ideas and/or tweaks old ones. in fact It looks smaller than the "snarl" of wire and components than he had spread across his home built board for a basic distortion circuit.
Thanks so much for these videos! I'm doing a Filmo amp mod and this is pure GOLD! Did you put the Trem circuit into the front of the 5879 preamp tube or after? Thanks again!
Doug, I stumbled on your videos when I was thinking of building a classic style amp cabinet for a Fender Blues Jr. and now I am hooked. I have not viewed all of your videos yet, but have seen about 15 or 20. I have a few questions you might think about addressing. Remember I am a musical instrument consumer, but really know little about most of the circuitry that you discuss, so my questions will be very simple. Please explain the types of amplifiers (class a, ab, etc) and if you have examples of a few in your shop, tell us the different sounds or other implications of each. I have a class A amp so this topic is of interest to me. Also, address wattage and loudness (clean). From some information I read, 5 watts to 50 watts is not 10 times as loud. These videos are great for guys like me that wonder what circuit gives us the sound we want. Thanks.
Excuse my ignorance, I'm a beginner. In theory, if I wanted to power to 12v dc peripheral off of the amp couldn't I wire it to the filaments of the 12ax7 tube similar to what you did with your pilot light on the oscillator tube? Would this change the amps performance? Thanks!
The filament voltage is AC, Curtis, so that may present a problem. However, if you could use AC, and your power transformer had a 12VAC winding for the 12AX7, and you didn't intend to use much current (like a few mA)....you could probably do as you suggest.
No, like most power transformers, this one has a 6.3VAC winding. Because the 12AX7 tube has a center-tapped filament, you can wire the tube so that the 6.3VAC becomes 12.6VAC.....but only within the tube itself.
Thanks for sharing this great conversion - I read through, and couldn't see anyone else ask this, so I'll throw it your way. I know the Filmosound 385 is the amp typically converted for guitar, but do you know if others from the same time period (eg, 621, 622, etc), would be also suitable? I'm in Australia, and these models seem to be available, but not 385. I wonder if they would have had basically the same amplifier construction, but other features on the projector to discern between models? BTW, it would appear Rusty's doppleganger lives next door to me. He's a red heeler I think, and (aptly), also called Rusty. He barks a lot - he's like the local granny, peeking through the blinds, to see what's going on in the street, and letting his owner know when anyone's around...
I'm not familiar with any of the models you mentioned, Ian. If you could provide links to schematics for each, I could offer an opinion on their potential for conversion. Heelers make great watch dogs......they always assume that strangers are going to steal their food :)
@@UncleDoug Heh heh. Next door's Rusty still barks at me every time he sees me, even though he sees me talking to his owner regularly... I'm still searching for schematics, but I did find this link to the conversion of a Filmosound 621 guitar.com/guides/diy-workshop/diy-workshop-bell-howell-filmosound-amp-conversion-part-1/ Also, I meant to ask - would the fact that it's a mic input (most likely having different impedance than for guitar), have an issue on compression?
Hi Uncle Doug! I've been subscribed and watching your video's since you launched your channel. I've learned so much and have rebuilt about a dozen amps thanks to the knowledge you've divulged. Thank you! Question on this video and the way you connected the negative feedback. Since you disconnected the 8 ohm output transformer tap from the speaker transfer jack, wouldn't that also disconnect the negative feedback circuit? Or is the negative feedback connected to the output transformer 16 ohm tap and thus connected to the 8 ohm tap as well?
G’day Uncle Doug I’ve got one of these but it’s from the 1940s. My Dad got it from American soldiers up in New Guinea during the War. So it runs on 110v and we have 240 in Australia. It came with a huge external transformer. I have a remote speaker he bought for the projector and I would like to set it up so I can pull out the amp and use it with my guitar and also be able to use it for films. Would it be possible to replace the internal transformer so it would run on 240 v or is that not really possible?
Uncle Doug, did you have to use that variable resistor to set the B+. I got mine up and running on a limiter at 80V, but then blew a fuse when i went to full power. I will check bias tomorrow and might just adjust that big R. BTW have you seen that version of the amp on youtube where the gain and volume are quite pronounced.
Yes, the variable resistor must be adjusted properly. If you blew a fuse, however, I doubt if it had to do with the resistor setting. Check for short circuits and leaking filter caps that might increase the current flow beyond the rating of the fuse. You also should be using a Current Limiter with any new start-up. It will protect the circuit components (and fuse).
Great mods, I have one of these amps and would like to change it but I looked on line and could only find the older octal schematic on line. Can you tell me were I can find this schematic. Thanks Craig in Texas.
Thanks, Craig. It's been a while, but as I recall this schematic came from an operator's manual for the B&H 385 that is listed on line. You have to download the PDF file and scroll through it to find the schematics. I don't have a link. Good luck.
These videos are very enjoyable, and also very informative. I have been wondering if a decent guitar amp could be made from TV tubes, since those are plentiful. Maybe would build one for my brother.
Thanks, Mr. TM. I don't believe that the vast majority of TV tubes are applicable to guitar amp use. You're better off sticking with traditional tubes for a home build.
Thanks, Mr. T. I'm sorry but tubes are special for each application, and TV tubes, in general, won't work well for audio amplifiers. Proper audio amp tubes are readily available, so this is not really a problem.
Great Job on the video! This little guy was a ton of fun to work on and your video was very helpful. Just finished modding mine and its sounding great except for one little issue I cant seem to resolve. There seems to be a noise issue that sound like constant static that is unaffected by gain controls. I replaced all of the plate carbon comp resistors, replaced all of the caps and tubes for a slight improvement. Can the carbon comp resistors in the tone stack cause static noise as well? I think its coming from the 1st 12ax7 stages in the signal path but I'm not sure. I'm at the end of my rope so any help would be great! thanks Uncle Doug and keep up the good work!
Thanks, Kyler. Any noise that does not respond to the volume control must come after the VC in the circuit. As you mentioned, carbon comp resistors can be noisy, but generally only in the portions of the circuit where significant current flows.....such as the power supply (especially just prior to screen lead) and plate circuit. Noise is probably the most common and difficult problem to diagnose, especially long distance. My approach is to chill (freezing spray), wiggle, replace, jumper, and systematically eliminate each possible source.
Hi, Thanks for this great video ! Had a question I was hoping you can help me with. How important is it when replacing the filter caps to have exact capacitance value? I understand you want the same or higher value when it comes to Voltage rating, But what about capacitance value? I am having trouble finding 15uf 450V axial. Thanks !
You're welcome, TOB. From my experience, you can safely go up in capacitance by a reasonable amount, i.e. up to 20 to 22uf instead of 15uf (if you can't find it). Problems only seem to arise if you double or triple the suggested value, which can place an initial current burden on your rectifier tube.
Uncle Doug, as always great information to be found on your video pages. In regards to adding capacitance. Isn't that initial current draw on the rectifier only really affected by the first filter cap in line.? That is also the one with the highest B+ isn't it. Can't you safely go up on capacitance for additional filtering in the later caps, especially the ones that are in the preamp or early stages where eliminating as much ripple as possible is the most important. since if I'm not mistaken any noise will be amplified. More comments and info on this subject gladly accepted.
Thanks Doug! Really like to watch these videos. What would you suggest for a "first timer" project? I have some experience but, its like 10 years ago in school, I build a small solid-state guitar amp. So i know the basics, how to read schematics, and solder. But not much then that. 2/3rd year I just build acoustic instruments. mostly basses and guitars.
I'm not sure if that's good or bad, MD, but I tend to put lock washers under nuts to keep them from unscrewing. One might be a little off center......so I'll correct it :)
Lol, I asked about the NE-2 bulb on your previous video and you answered it here. I just finished this project myself. I thought it was drawing a little too much current and I used a 470 ohm resistor to bias the 6v6’s. It brought down the current but the plate voltage went up about 30V. Seems ok since the plate dissipation is around 11W for both tubes. Was I wrong about changing the cathode resistor or is that an ok mod?
It's the only way to alter the bias, TN, so you were wise to do so. The PC and PV are inversely related, so when one goes up, the other always goes down.
@@UncleDoug I see. That inverse relationship did surprise me since I’m used to just looking at ohms law where voltage and current are directly proportional.
Great video, UD! My 385 didn't have the speaker jacks labeled, don't remember how I determined 8 and 16ohm, have to look at. Mine is definitely dull with the NFB like you say. Also, mine hisses (not hums) really loud when you turn up the tone to the treble side. I removed the photocell which caused hiss originally. Any ideas there? Does yours have anything like the low-end thump of a Princeton Reverb now? That's what I'd like to shoot for. Thanks!
Hiss has not been an issue on mine, so I have no experience eliminating it. Generally, the cause is carbon comp resistors.....so you might change them out for metal film resistors. With the NFB turned down and a proper speaker in a good enclosure, I feel that the bass response is quite good.
Thanks much! Probably a winter project for me, really a novice at this point, but your vids are helping! Not sure if I asked you this before, but do you do conversions for other people?
I have a cabinet I built for a bell & Howell the version without a power transformer . I decided to scrap the project in favor of a amp with a pt anyway I really enjoy your videos and would like to give it to you it's just the shell very compact and unfinished but it's a really good head start really tight box joints I will try and private message you
I expected that old projector amp would come alive and it certainly did. There's a nice fullness to the sound that I prefer over the 5F1\5F2. Whats that green monster behind the 36? Your shop looks like an interesting place to spend the afternoon but I think I might need need some type of alcohol based liquid cooling to deal with those 111F temps. I thought 97 was bad here in the south. It's not even July. WOW!! Thank you again for another informative video.
Thanks, Sluggo. The vehicle under the tarp is a really nice 1952 Chevy pickup that I've been working on. I try to shield it from the sun, but it's a waste of time.....much like trying to shield a pine tree during a forest fire. The other day while working on it, if I set a tool down in the sun for more than a few seconds, it quickly became too hot to touch. I had to quit, put on some gloves, and then carry the tools into the "shade" to cool down.....to 110.
I would think that in the dual 8 ohm jack version, it was used to drive two speakers, one on each side of the 16 mm screen on a gym stage where more coverage was necessary, Rat's nest wiring technique from the original factory build. Good effort with all your improvements but to me it is not what I would call an inspiring amp if I had to play my guitar through it. Those 283 Chevys were neat engines. With a 4 barrel you could get good performance from it. Nice little truck.
I've read that the Canadian guy you refer to who popularized modding these vintage B&H amps - Bernie Rausig - reportedly modeled the tone stack of his builds after that of a vintage early '60s Vox AC-15. Does your build follow that lead or did you leave the tone circuit stock?
I love that you added tremolo. I've always wanted one of these Filmosound amps but the lack of tremolo held me back as it has become the effect I use more than any other. If you ever decide to sell, let me know. I just may be your Huckleberry. Thanks for a great video.
By coincidence, I was working on it yesterday. The tremolo has developed a thump, which is very common.......but I don't like it and am going to try to eliminate it or at least reduce it quite a bit. If I can, the amp would be for sale. Other than the "thump" it works and sounds great.
The NFB is not the bad part of the tone. Austen hooks leaves his in. More to do with voltage and swapping ip.coupling caps and other parts for hid atleast. He uses 15k NFB resistor
Thanks, Craig. Yes, it is a densely wired little rascal. I used black silicon gasket sealer, just in case the chassis was used with a metal base plate and one of the joints drooped a little.
I just watched this series again because you are careful to match the tubes and adjust the bias. My question is about tube swapping. There are currently many headphone and hi-fi tube amps being sold. (I like the resurgence of the tube circuits) I am, however, somewhat mystified by some of the practices being professed. Many of these new amps are being marketed as having the ability to swap tubes out willy-nilly. If you want to change try another type of tube, just pull and plug. I have asked the sellers about setting bias and/or matching but have general received the answer that it is not necessary. I would have thought that making adjustments would be more important for hi-fi/headphone amps. Are these new amps immune to such needs because of some sort of magic tube fairy dust? Or will the modders be met with the possibility of premature tube/circuit failure due to the imbalance of it all? Sorry if OT, I didn't know of a better place to ask my noobish questions. Thanks.
Greetings, CK. Cathode biased output tubes tend to be "self-regulating" with regard to plate current, and this ability generally allows you to change tubes in such circuits without having to re-bias after each exchange. I assume that the amps you speak of are all cathode biased. This makes for a good sales pitch, but in my opinion, it never hurts to double check the bias from time to time. Bias resistor values can vary with use, and some of the newer tubes operate at voltage and current levels that may differ so greatly from those for which the original bias was set, that you really need to take occasional measurements to be sure everything is OK.
I just added links to schematics in the video description, BMR. Here they are, I hope they are adequate: app.box.com/s/66hevc3qk0cqju83w1zpbozypyfgbfvu and app.box.com/s/3h56lk7ma36qomyscxgs5eojmhb8xd1t
Jack and Rusty did a fine job with that amp Doug!She really came out sweet so far, I'm quite impressed my man *thumbs*There is a neat old Filmosound sitting here waiting on a conversion, however she has a LOT more room inside.Would you like to see?How do I send you an image, you might like this one?John
Thanks, John. When they wake up for breakfast (around 11AM) I will let them know :) You are welcome to post photos on my Facebook page: Uncle Doug's Vintage Amps.
I'm still having trouble with the noise level. Otherwise great sound from this amp. Still need to change the 7851 and 5Y3 tubes to see if they're the cause. Seems to be a regular complaint on a lot of forums. Anything else I should try? Learning a lot from your great vid's. Thanks.
Noise elimination is a complex issue, not easily diagnosed long distance, Vincent. I think you should focus on lead dress, bad connections, carbon comp resistors, etc. Good luck.
Having two of these amps sitting on my bench, I was very pleased to see you embark on this filmosound project amp. It was indeed a difficult project for an newbie like myself. With your youtube assistance I was able to follow your instructions and get through it. I did not add the tremolo (one must know their limitations) but now have an amp for some closet harp playing. Thank you. Couple of Q's. I assume I don't need the 20 mf cap that's part of the oscillator circuit and do I need to replace all of the small caps to rid it of the hum I still have even after replacing the can electrolytics? I also noticed that you have a 33 mf cap in use and wondering what that was for? "Like an old married couple ........" loved that part. Lol :-)
Greetings and congratulations on a successful conversion, Vincent. No, you don't need the oscillator cap, nor do you need to replace the smaller caps to reduce hum.....it generally won't help. You should focus on lead dress and the tubes themselves to see if they are the cause. I don't recall the 33uf cap......perhaps it was the closest value I had on hand (?)
As I recall, it came from Radio Shack. If they are still in business in your area, Pete, they generally have a nice selection of such bulbs and lights.
Thanks Doug! found the last Radio shack in my area going out of business sale the other day and got a nice flush mount pilot light. I'm working with the M-2 385. How would the pot work for the NFB issue? Since there's only one winding on the secondary where would the feedback resistor and pot be place?
Greatest sounds! the truck is your new guitar amplifier project? sorry, just kidding ;) pretty cool too. about the project... crazy! Perhaps you are the amplifier magician?
I always hit 'like' on your videos even before watching them cause I know it's a safe bet.
Thanks for the vote of confidence, Brad. I value your opinion and always appreciate hearing from you.
The feeling is mutual.
@@TheGuitologist If I didn't love you both I'd tell you to get a room.
Another great project. Nice work Uncle Doug! I see Rusty is in his usual work mode and now Jack appears to be photobombing! Have a great day!
Thanks, Dave. Yes, everyone was up to their usual tricks :)
Excellent content. You are a very talented and creative engineer.
Thanks so much, 753 :)
Nice work Rusty! Oh yeah, you too Doug... :) The NFB work and Tremolo really helped make it a nice guitar amp. Top shelf work and knowledge as usual Doug. I learn new stuff every time I watch your videos - Thanks!
You're welcome, CA, and thanks.....from both of us :)
Thanks so much, I got one of these amps a few years ago, and just picked up a projector speaker cabinet to match. It will be put together to make a kick-ass instrument amp!
Great job. Considering what it sounded like when you started that's a remarkable improvement.
Thanks, Galf. There is still some room for improvement, when I get some free time :)
Your work is amazing! I haven't worked with tube amps, but I understand the basics and can see how much work went into this. Thanks for sharing it!
You're welcome, David. Thanks for your nice comments.
Very nice! My former B&H colleague watched part one and found it to be interesting even as he reminded me he was on the mechanical side of engineering. Myself as well during my tenure. All the best!
Thanks, JC. I am flattered that an original B&H engineer would watch one of our videos. I'm glad he found it interesting.
I've been a HUGE fan of these systems that were used by Bell and Howell. The first thing I noticed was the 25 watt Jensens in the little cabinets! They were the first thing I fell in love with. And I played one forever! Still in the little Bell & Howell cabinet. People would ask me all the time, what was my guitar amp? I would tell them FILMOSOUND... then there were OTHER people using them at gigs. And I began to seek them out. Eventually I got FOUR of those 25 watt jensen loaded cabs and screwed and epoxied them all together and made a FILMOSOUND half stack (a four 12 cabinet) and played that for a long time. The Magnatone I'm playing through at the moment has a late 50s/early 60's filmosound speaker in it, which i think is a Heppner? It's wonderfully bright and differs from the Jensen with an aluminum dust cap and actually superior sensitivity and breakup at higher volumes... certainly the best speakers for guitar I've ever owned started off in Bell and Howell cabs... I have a bid on one of the old 6v6 amps from what appears to be the early 50's or even late 40s... hope i win it! lol
Great project Doug! Really enjoy the conversions. Trash to treasure. Many of your videos helped inspire me to re-purpose a non-functional Epiphone Valve Junior head I had lying around into a hand wired 5F2A Tweed Princeton clone. I learned a ton and now have what has become one of my favorite little tube amps!
Thanks, Kley. Rusty and I are glad the videos were inspirational :)
Thank you Uncle Doug, What an awesome project. Great explanation for someone not well versed in electronics, like myself.
It was our pleasure, Steph......glad you enjoyed it.
Another great video Doug, thanks! Every time I watch one of yours, I get the hankering to clean off the workbench in the garage and finally start that 5E3 project that's been going through my head. I feel that now I'd know what I'm doing, as opposed to just following a recipe and soldering things together without knowing their function.
I like how you go from snow to blazing temps there. I was in White Sands a few weeks ago when it was 106 out. "But it's a dry heat" as they say! Thanks again and keep up the good work.
You're welcome, Mark, and thanks so much for the nice comments. We're glad the videos have been helpful. White sands is only about 80 miles away.....and, yes, it may be a "dry heat", but at 106 it's still darned hot !! :)
Another great build!! Can't believe wait for the next one. You have taught me a lot and I think you for it. Keep up the great vids!!!
You're welcome, Chris......glad you enjoy the videos :)
That is a beautiful Chevy! Love the baby blue with orange flames. Serape is a very cool touch. I look forward to learning more about the Bell & Hell 385. Thanks UD
You're welcome, Brad. Glad you like it :)
These videos are so much more informative then the old Mr. Wizard shows I watched as a kid.. that just dated me!! Thanks Uncle Doug!! Not much screen time from Rusty and Jake.... probably to busy inspecting next project..
Thanks, Luth. You're welcome for the video. Rusty was studying for his pilot's exam.
Thanks for another great retrofit-conversion video. You are an inspiration! I had previously built a clone of the 64 Princeton Reverb and found that the tremolo oscillator was sensitive to component lead length and/ or wire length to the speed pot. You might have a similar issue on this amp. That hot rod is a real beauty! Stan
You're welcome, Stan. You may be right. With the long leads used during my mock-up, it sounded perfect.....dead quiet and great intensity. One I installed everything with the shortest leads possible, some of the properties changed. I will continue to work with it and iron out the small "wrinkles". Thanks for your good advice.
Great "mini series" of a fab re-purposing!! Your work is always amazing, thanks for sharing! I see Jack is forcing his way into the vids......The You Tube fame has definitely gone to his head! That truck is a real work of art!
Thanks for all your nice comments, Tim.....we always appreciate hearing from you :)
the clips and hooking stuff up before locking it in is brilliant. this could be done with guitar pickups and other gear before soldering it in. brilliant!
Glad you like the technique, AB. Thanks !!
It is brilliant but a word of warning from personal experience. I had several alligator-clip jumper wires just like these and I found to my surprise that over time, the dissimilar metals involved set up a slow corrosion process in between them to the point that the jumpers measured as much as 20K of resistance! I wound up just going at the clip connections with a wire brush, hitting them with liquid flux, and soldering the area where the wires were crimped in with extreme prejudice. That solved the problem.
Hi Uncle Doug, Rusty & Jack, Another awesome conversion by the Master Amp Builder! Not one for a beginner or the meek. I think I will stick to the 5F1 or 5C1 for now, a little more my speed and that aint sayin' much. Lots to learn, but, thanks to you, I think I can. I was waiting patiently for part 2 and well worth it. Glad to see again, you truly are the best. Take care, C.
Thanks, Cass. It was like building a ship in a bottle filled with barbed wire......pretty tough. Rusty, Jack, and I really appreciate your kind comments, however, and are always glad to hear from you.
Thanks for showing the truck. We got a glimpse of it early in the vid and you had me interested... Also, great work on the amp as usual!
You're welcome, Greg. I thought the little "teaser" early in the video might catch your eye :) Glad you liked it.
that was a right tight space to work your magic in Doug. I used to live out west. Love those old cars too. Don't remember rust being much of an issue back then...Anyway, great video about the amp conversion. Lookin forward to your next adventure!.
Thanks, YRU. It was a challenge, like trying to cram 5 lbs. of linguine into an 8 oz. take-home box. You're right about the absence of rust.....it's generally not an issue in local cars. Glad you liked the video :)
Great project Uncle Doug! Again! That tremolo is an absolute winner! By the way, I have an old RCA MI12161 converted to a Fender 5C3 Deluxe amplifier! It sounds similar to this one!
Thanks so much, Oura. I really appreciate your nice comments :)
Aphexon: You need to change your privacy settings if you want me to respond to your questions.
You're welcome, Aphexon. I always recommend a simple Fender 5E1 or 5F1 Champ as the best first project. Please see my video series where I build one from scrap parts and incorporate some upgrades. Good luck with your project :)
Bulbs are sometimes used as ballast resistors to reduce or limit current in a circuit, such as in the input circuit of some organ amplifiers. They are also used in the photoresistor tremolos found in the larger Fender amps (Deluxe Reverb and above).
Hi Uncle Doug. I'm a little late to this video being I just picked up a B&H Film Projector amp. Do you take customers? I'd like to have this done to mine.
@@deebojones Sorry, Darin, but I no longer do conversions. My purpose in creating and posting videos is to instruct you in doing the job yourself. Best of luck.
Very cool Doug. I will be starting a first time amp conversion myself shortly and I think I will go with the 5F1. I will make a video series from it as well. Have a great day - Regards, Ron
Thanks, Ron, and best of luck with your project. Be sure to let us know how it turns out :)
nice Tremolo Uncle Doug! So glad you make these videos. Little by little I'm learning stuff as time permits Today I installed an Ampro deluxe 12 inch speaker from 1957 or 47 to replace an ageing and failing 1946 Jenson in my 1946 Masco Map 15 guitar amp.
Thanks, Bruce. Rusty says that anyone with a 1946 Masco amp is OK in our book :)
Uncle Doug, awesome work as always! Great amp and a lot of useful info as well. Tremolo sounds incredible! I realy love this new "conversion" series. Happy you now have better video quality - looks just perfect. And it seems I have some new materials to work with, huh =)
Wish you good luck in future projects!
Thanks so much for your very positive comments, GW. Rusty and I really appreciate it......and wish you the very best :)
Marvellous explaining with a warm heart!♡
Thanks, JH.
Fantastic!
I think ol "Jim Bob" on the Walton's TV program had some similar rods in his day.
Along with "Wally" on "Leave it to Beaver", if I remember correctly.
I think "Ward" used the term "Jalopy" back in the day ; )
Back, when all you needed was a summer job, some basic shop tools, a salvage yard nearby and a buddy or two to help out occassionally. Just an fyi, there is a website dedicated to the main cars in the movie "American Graffiti".
The deuce had a 327 Chevy in it with some Stromberg's up top. The 55 Chevy was one of three 55's that were built for the movie company and each had 454 BB's in them, as you can "hear" that's no small block Chevy in 1962!
I was right about that before I found it years later on the web. Also, the 55 that was supposedly wrecked by Harrison Ford was not. It was a salvage donor car that was a hardtop that they used a 2X4 as a post in the movie to make it look like a 2dr post and if you watch you can see it burning when upside down in the ditch.
That's Hollywood!
Another one of the 55's was used in the movie "Two Lane Black Top" with James Taylor and Dennis Wilson.
I don't recall about the third 55?
I'm sure that it's obvious by now that I'm a car nut..
Thanks for the info, Amo......very interesting :)
Thank you for this explanation Uncle Doug, this was interesting.
You're welcome, Buddy.....glad you liked the video :)
As long as You and Rusty agree thats all that matters! Thanks again!
.......and if we don't agree, trust Rusty :) You're welcome, Mark.
The tremolo sounded fine on the video. Intermittent problem’s are always fun. I really wish you’d have recorded some audio of yourself pulling out those horizontal can caps! They looked really fun as well,lol! Great results tho!
The neighbors got to enjoy the commentary while I worked on the cramped little %@$#&?% chassis, William. You're lucky to have missed it.
Hey, Uncle Doug, I'm from Brazil! I've got one! It's amazing!
Greetings, Mario. I'm glad to hear it ;)
Excellent video - as usual !! I loved your "prototyping" approach - simple - elegant !! And what a great learning process - to put in a pot and audibly listen to the effects of feedback in the circuit. Personally tho - I think after having heard the feedback stifling the life out of the amp - I'd go in an rip it all out. No feedback sounds great !!!
Thanks so much, Donald. Dynamic testing like this is, to me, the easiest and most effective way to optimize tone. I agree that excessive feedback, so often employed in conventional amp circuitry to increase headroom and protect speakers, really smothers the raw power of the amp. Having it be variable definitely makes sense.
Excelente....siempre pensé que no se podían convertir estos aparatos viejos en amplificadores, debido a que dicen que el transformador de salida de guitarra es distinto al de audio.
Gran explicación Uncle Doug
Saludos
Gracias, Diego. Rusty y yo estamos contentos de que hayan disfrutado el video. Sí, amplificadores de este tipo pueden ser fácilmente convertidos para usar la guitarra. Debe hacerlo por uno mismo. Los mejores deseos para su éxito.
Great modification on the NFB-loop. It's like the amp can breath freely. It has a remarkable sustain characteristic with the root frequencies intertwining smoothly with harmonics and resonances as they fade. Very interesting video about a very remarkable conversion. I'm still puzzled how in the Lone Star State you manage to get snowstorms at 111°F, but that's probably a micro-climate-thing as your videos are too cool for deserts to uphold their temperatures :) Thanks for sharing that!
Thanks, KL. We don't generally get both the 111 degrees and snowstorms at the same time.....Rusty used time lapse photography to make it appear so :) Glad you liked the NFB modification.
thanks. i have one of these on the shelf, waiting for me to find time to tear into it.
They're rather cramped and claustrophobic, Joe, but they sound great !!!
I was immediately repelled by the congestion I found in mine, obviously built in layers, with not much thought given to service, but I decided that someday I would probably have time tounsnarl it.
I really like how you moved the bias parts and mounted the tremolo on that hum sheild.
I sort of imagine that I would find a way to add a reverb tranny to drive a spring off that extra 6V6, but your trem is very cool. My all time favorite trem was the one on my brownface Deluxe.
The best tremolo I have personally encountered is the Vibrato (harmonic tremolo) in a brownface Concert amp. The brownface Fender's were an excellent, but rather briefly offered, series.
I had a pair of them, a brown deluxe in a mahogany cabinet with a D-130 in it, and a brown super in a poplar cabinet with hand cut dovetails and a pair of D-110s but methrats broke into my shop and stole both of them. :( Amazing sounding amps, both of them.
What a terrible loss, Joe :(
got me looking for old stereo stuff !! you and brad,, good stuff man, learning a lot !! g.k.
That's good, Gene. Happy hunting :)
have a super 4th uncle D. got a backlog of your vids to watch. all saved to favs. keep cool bud.
You too, RH. I hope you enjoy the videos. As my old granny used to advise us on the 4th, "Don't hold your firecrackers too long before throwing them" :)
As my aged theory taught me. "You'll be a statistic!".Throwing fireworks at each other much more fun makes tho.....
muito obrigado por ensinar muita parte importante sobre amplificadores
fui aprender a tocar guitarra em 1968 logo tivemos construir e consertar
nossos amplificadores até hoje estou aprendendo muito com o Sr. obrigado
amigo por todo material divulgado um abraço Sul do Brasil
Você é bem vindo, Jorge. Fico feliz que os vídeos tenham sido úteis.
The photo electric cell (PEC) from an optical film sound pickup that was the original input to this amp are very bright so it makes sense to have the NFB cranked up to reduce that brittleness.
That cell is not used when the circuit is modified for guitar use, John.
My "starting point" was the "Lauren" amp at TedWeber. The Schematic and layout are on their site. It was built based on a 50's Princeton. Bigger Xformers, Bigger filter caps, and it was ready to go. I had to wrestle with a high B+, and keeping the screen voltage at 300... Some tweaks were needed to it to get it stable.
He must name his amps after his kids. Thank heavens they don't have names like The Hortensia or The Murgatroyd.
Excellent! That tremolo was very strong. Great part 2. If you do a build of a cabinet, you might try different coverings and grill cloth, such as a dark red(burgundy) and a wheat grill. Just a suggestion. I'm sure what ever you choose to do will be good. A head only would be nice also. Less weight and any combination of amp and speaker. Thankz
You're welcome, ATL. I'll keep your suggestions in mind. I too would like to try something different.
I need to replace the can capacitors in my filmosound 302 amp and am curious as to where you found those axial capacitor replacements for your 385. In my amp they're mounted on top of the chassis but are still gonna be a pain to replace.
Thanks
You can get both types of capacitor from Antique Electronic Supply.
Thank you
Enjoyed that video!
Glad to hear it, 49 ;)
Nice tremolo sound. I like the "breadboarding" technique, just takes a little more counter space than the "modern" style. :)) Beautiful work as always. Was Jack attempting a Hitchcock type cameo? Nice looking car.
Thanks, Andrew. Yes, this is my version of "freeform" breadboarding :)
What a nice little amp. Great project Doug. Love that truck. A friend of mine had a 1951 5-window Chevy pickup back in the late 70's 3 speed manual with an LT-1 350. That was a running little truck. A big oak tree dropped a limb on it during a storm. Total bummer. I had a '69 SS 396 4 speed Camaro until I got married. I should have kept the car. Before the Camaro I had a '69 Dodge Dart 340 4 speed. I gave up hot rods for lent (not really). Actually... the section of the brain that says don't got fast to normal people is defective in my brain. Abstinence keeps the insurance rates low :o)
Thanks, Michael. Like you, I've always enjoyed old cars that go fast. My high point, however, was buying a brand new 1965 GTO with Tri-Power and a 4-Speed, that I proceeded to run, literally, into the ground, like the juvenile idiot that I was at the time......but darn, was it fun :) The final indignity came when I traded it in on a new Toyota Corolla 4-Door after I got married and my daughter was born. The trade made sense at the time, but I still wake up late at night in a cold sweat just thinking about it :)
Thanks for sharing , Great looking Truck .
You're welcome, W4, and thanks :)
Excellent video. Thank you.
You're welcome, CB :)
I am convinced that this is exactly the amp Tommy James used :)
Rusty is pals with Tommy and will ask him about it the next time they get together, RR :)
Good lord Doug....pics of the Hot Rod!!!
You are one groovy Daddio haha
Thanks, Chout :)
Great channel, great content, great dog. Say hi to Rusty from me. Keep up the great work!
Thanks so much, Mats :)
Back in August, 2008 I was blessed to have gone to Gerald Weber's amp camp in Kempner, Texas. I also have his books and videos. He stated that if you have a output tranny that has 8 and 16 ohm taps, your better off using a 16 ohm speaker connected to the 16 ohm tap. He said you will enjoy the full output of the tranny because you are using all of the windings.
Please comment. Thanks, Eric
That is correct! :)
If Gerald said it, then it must be true, Eric.....and it does make sense.
Is the 100k pot in the NFB circuit hooked up as a variable resistor with pins 1 and 2 tied together?
It is wired in series and used as a variable resistor....but the wiper is not connected to either of the other pot lugs.
Uncle Doug: Thanks for your videos - I have learned so much from you and them. I am presently converting an old Victor stereo console chassis (complete with original PS) to a guitar preamp platform. It was one of those big old wall units that had been left in a barn.
It had a set of EL34 as power tube sockets which I have converted to one EF86 and one 12AX7 sockets for a preamp stage (output to guitar amp input). The other tubes in it were two 6AV6 and two 6BA6 mini tubes. The 6AV6 is very similar to one stage of a 12A. I would like to add a tremolo to the chassis using the 6AV6. Do you think the VibroChamp would work there if I employ one 6AV6 per side of the tremolo circuit you employed here?
You're welcome, James. The VibroChamp tremolo circuit is a good one. I'm not sure about a 6V6 working well as an oscillator tube. You would simply have to try it and see.
@@UncleDoug Hi,
thanks. Just making sure your reference to a 6V6 not a 6AV6 was intentional or not? The 6AV6 has a triode configuration that can be used, I believe, like 1/2 of a 12A.
Thanks Uncle Doug. Always a pleasure to watch you work. Didn’t get to hear the amp on full Treble, although I noticed it had been moved from the central position on the very last shot….
Glad you enjoyed it, PC.
Hello, im Facundo from Argentina...I recently adquier 3 speakers and one amp from old image and sound projectors, the amp and one cabinet with the original speaker its a RCA, the speaker its 10" and 8ohms, i think 15w, and the other two speakers are one Jensen with the cabinet from Bell & Howell 12" 16ohms and 15w, and the last dont have cabinet yet but its a Goodmans 60 12" 16ohms and 15watts to...My question is about the wattage of this old amps from the projectors, i cant get the schematics and i am very new in electronics, do you know if this speakers can handle ok with this kind of amps? the 3 are 15watts speakers, i dont want to brake nothing...Well thank u very much!
It sounds like the 3W speaker has no hope of survival and the 15W speaker won't last long if you run the amp at full volume.
This is another great job.
I'm looking at your suggestions concerning the specifications of the 6SL7. Can the tube be used in a so called single tube push pull circuit?
Is there such a thing?
Thanks, Stuart. No, there is no such thing as single-ended push-pull. The tube is best suited for pre-amp use.
How did you get the chassis that clean? i just got a Model 399 "Specialist" that seems to have the same amp, but its pretty grimy!
It was clean to begin with, Riggs. Sometimes I just get lucky ;)
I'm really learning a lot from your videos. I have a Premier-20 16mm projector with an audio amp but the power transformer is bad. Where would you suggest that I pick up a good one for a reasonable price? The only number on the transformer is 18385. The windings are just like the one you have here in this B&H. I would like to remount the components in a custom chassis and replace the capacitors. I also have the Ampro speaker but the cabinet is in bad shape. It may make more sense to build a guitar amp from scratch. I recently retired and I think this would be a good project to take on. Last time I worked on electronics was back in the 80's. Thanks.
It does sound like a good project, RB. I get all my ClassicTone transformers from Amp Parts Direct.
I have a Bell and Howell 300M reel to reel recorder I was debating turning the tube amp into a guitar amp
Others have done it, C&C.....with good results.
Hiya Uncle Doug! I have this same amp and the volume + tone pots on mine are shot. They are noisy/crackly and I would like to replace them (with an added on/off toggle switch). Do you have any suggestions as to what kind of pots I should use for replacements? Thanks for the videos! They’re all great!
You're welcome, Payton. Here is where I buy mine: www.tubesandmore.com/search/node/pots?page=1 You can't go wrong with CTS or Alpha pots.
Great tremolo sound! I have a couple of 1950s Bush radios which make great guitar amps with a great sound, they have pickup sockets in the back so you just need to make an adaptor and plug straight in, one I picked up recently has quite a hum on it though, quite a few wax caps and I can see at least one is over heating, I'll change the caps and see what happens.
Thanks, Adam, and good luck with your project.
Sorry for two comments in a row!
That hotrod Chevy is great. I also love working on those kind of projects. I helped a friend install a fuel injected engine into his 1933 Dodge pickup. We installed a Chevy 350 'tuned port injection' engine with 700R4 transmission.I had to do the ECM wiring and tuning. We got the engine running well, but my friend passed away before the entire project was completed. Here is a picture of the project: 68.209.87.173/33_Dodge/33_Dodge_2.JPG
Thanks for the photo, David. It's a shame your friend did not get to see the project through to completion.
9:20 U.D. I'd say your methods and techniques are pretty solid. You are working on the same wavelength as Brian Wampler of Wampler Pedals that looks very much like his youtube video on how he breadboards new ideas and/or tweaks old ones. in fact It looks smaller than the "snarl" of wire and components than he had spread across his home built board for a basic distortion circuit.
Thanks, Murry.
Thanks so much for these videos! I'm doing a Filmo amp mod and this is pure GOLD! Did you put the Trem circuit into the front of the 5879 preamp tube or after? Thanks again!
Thanks so much, 98. To be honest, I don't recall. Hopefully, the answer is in the video itself. Good luck.
Doug, I stumbled on your videos when I was thinking of building a classic style amp cabinet for a Fender Blues Jr. and now I am hooked. I have not viewed all of your videos yet, but have seen about 15 or 20. I have a few questions you might think about addressing. Remember I am a musical instrument consumer, but really know little about most of the circuitry that you discuss, so my questions will be very simple. Please explain the types of amplifiers (class a, ab, etc) and if you have examples of a few in your shop, tell us the different sounds or other implications of each. I have a class A amp so this topic is of interest to me. Also, address wattage and loudness (clean). From some information I read, 5 watts to 50 watts is not 10 times as loud.
These videos are great for guys like me that wonder what circuit gives us the sound we want. Thanks.
You're welcome, JD. Thanks for the suggestion. I will keep it in mind for a future video.
Excuse my ignorance, I'm a beginner. In theory, if I wanted to power to 12v dc peripheral off of the amp couldn't I wire it to the filaments of the 12ax7 tube similar to what you did with your pilot light on the oscillator tube? Would this change the amps performance? Thanks!
The filament voltage is AC, Curtis, so that may present a problem. However, if you could use AC, and your power transformer had a 12VAC winding for the 12AX7, and you didn't intend to use much current (like a few mA)....you could probably do as you suggest.
+Uncle Doug thanks Doug! I actually have the exact same filmosound as you're working on in the video! Does it have a 12v winding for the 12ax7?
No, like most power transformers, this one has a 6.3VAC winding. Because the 12AX7 tube has a center-tapped filament, you can wire the tube so that the 6.3VAC becomes 12.6VAC.....but only within the tube itself.
+Uncle Doug thank you Doug! I appreciate it, love the videos, keep up the great work
You're welcome, Curtis. Thanks. We will :)
Thanks for sharing this great conversion - I read through, and couldn't see anyone else ask this, so I'll throw it your way.
I know the Filmosound 385 is the amp typically converted for guitar, but do you know if others from the same time period (eg, 621, 622, etc), would be also suitable? I'm in Australia, and these models seem to be available, but not 385. I wonder if they would have had basically the same amplifier construction, but other features on the projector to discern between models?
BTW, it would appear Rusty's doppleganger lives next door to me. He's a red heeler I think, and (aptly), also called Rusty. He barks a lot - he's like the local granny, peeking through the blinds, to see what's going on in the street, and letting his owner know when anyone's around...
I'm not familiar with any of the models you mentioned, Ian. If you could provide links to schematics for each, I could offer an opinion on their potential for conversion. Heelers make great watch dogs......they always assume that strangers are going to steal their food :)
@@UncleDoug Heh heh. Next door's Rusty still barks at me every time he sees me, even though he sees me talking to his owner regularly...
I'm still searching for schematics, but I did find this link to the conversion of a Filmosound 621
guitar.com/guides/diy-workshop/diy-workshop-bell-howell-filmosound-amp-conversion-part-1/
Also, I meant to ask - would the fact that it's a mic input (most likely having different impedance than for guitar), have an issue on compression?
Gorgeous.
Thanks, John :)
Hi Uncle Doug! I've been subscribed and watching your video's since you launched your channel. I've learned so much and have rebuilt about a dozen amps thanks to the knowledge you've divulged. Thank you! Question on this video and the way you connected the negative feedback. Since you disconnected the 8 ohm output transformer tap from the speaker transfer jack, wouldn't that also disconnect the negative feedback circuit? Or is the negative feedback connected to the output transformer 16 ohm tap and thus connected to the 8 ohm tap as well?
Thanks, Stephen. As you said, if you are connected to one secondary tap, you are connected to all of them.
G’day Uncle Doug I’ve got one of these but it’s from the 1940s. My Dad got it from American soldiers up in New Guinea during the War. So it runs on 110v and we have 240 in Australia. It came with a huge external transformer. I have a remote speaker he bought for the projector and I would like to set it up so I can pull out the amp and use it with my guitar and also be able to use it for films. Would it be possible to replace the internal transformer so it would run on 240 v or is that not really possible?
You can order a ClassicTone power transformer from Amp Parts Direct, Scott, that will adapt your circuit to run on 240VAC.
Uncle Doug thanks very much. Love your videos by the way.
Uncle Doug, did you have to use that variable resistor to set the B+. I got mine up and running on a limiter at 80V, but then blew a fuse when i went to full power. I will check bias tomorrow and might just adjust that big R. BTW have you seen that version of the amp on youtube where the gain and volume are quite pronounced.
Yes, the variable resistor must be adjusted properly. If you blew a fuse, however, I doubt if it had to do with the resistor setting. Check for short circuits and leaking filter caps that might increase the current flow beyond the rating of the fuse. You also should be using a Current Limiter with any new start-up. It will protect the circuit components (and fuse).
Wait wait, you can get SNOW in a DESSERT area? The amp sounds great though. And that hotrod looks like one cool car!
Yes, we do, Clem :) Thanks !!!
Desert . One S . Otherwise it's cake
Great mods, I have one of these amps and would like to change it but I looked on line and could only find the older octal schematic on line. Can you tell me were I can find this schematic. Thanks Craig in Texas.
Thanks, Craig. It's been a while, but as I recall this schematic came from an operator's manual for the B&H 385 that is listed on line. You have to download the PDF file and scroll through it to find the schematics. I don't have a link. Good luck.
OK now I see the truck.
So nice...Daphne Blue almost.
Thanks, Chout :)
Thank you!
These videos are very enjoyable, and also very informative. I have been wondering if a decent guitar amp could be made from TV tubes, since those are plentiful. Maybe would build one for my brother.
Thanks, Mr. TM. I don't believe that the vast majority of TV tubes are applicable to guitar amp use. You're better off sticking with traditional tubes for a home build.
Thanks, Mr. T. I'm sorry but tubes are special for each application, and TV tubes, in general, won't work well for audio amplifiers. Proper audio amp tubes are readily available, so this is not really a problem.
Great Job on the video! This little guy was a ton of fun to work on and your video was very helpful. Just finished modding mine and its sounding great except for one little issue I cant seem to resolve. There seems to be a noise issue that sound like constant static that is unaffected by gain controls. I replaced all of the plate carbon comp resistors, replaced all of the caps and tubes for a slight improvement. Can the carbon comp resistors in the tone stack cause static noise as well? I think its coming from the 1st 12ax7 stages in the signal path but I'm not sure. I'm at the end of my rope so any help would be great! thanks Uncle Doug and keep up the good work!
Thanks, Kyler. Any noise that does not respond to the volume control must come after the VC in the circuit. As you mentioned, carbon comp resistors can be noisy, but generally only in the portions of the circuit where significant current flows.....such as the power supply (especially just prior to screen lead) and plate circuit. Noise is probably the most common and difficult problem to diagnose, especially long distance. My approach is to chill (freezing spray), wiggle, replace, jumper, and systematically eliminate each possible source.
Hi, Thanks for this great video ! Had a question I was hoping you can help me with. How important is it when replacing the filter caps to have exact capacitance value? I understand you want the same or higher value when it comes to Voltage rating, But what about capacitance value? I am having trouble finding 15uf 450V axial. Thanks !
You're welcome, TOB. From my experience, you can safely go up in capacitance by a reasonable amount, i.e. up to 20 to 22uf instead of 15uf (if you can't find it). Problems only seem to arise if you double or triple the suggested value, which can place an initial current burden on your rectifier tube.
Uncle Doug, as always great information to be found on your video pages. In regards to adding capacitance. Isn't that initial current draw on the rectifier only really affected by the first filter cap in line.? That is also the one with the highest B+ isn't it. Can't you safely go up on capacitance for additional filtering in the later caps, especially the ones that are in the preamp or early stages where eliminating as much ripple as possible is the most important. since if I'm not mistaken any noise will be amplified. More comments and info on this subject gladly accepted.
Thanks Doug! Really like to watch these videos. What would you suggest for a "first timer" project? I have some experience but, its like 10 years ago in school, I build a small solid-state guitar amp. So i know the basics, how to read schematics, and solder. But not much then that. 2/3rd year I just build acoustic instruments. mostly basses and guitars.
I always recommend a Fender Champ as the first project, Aphex. It's a fairly simple circuit and you will end up with a really nice amp.
Great work Doug! Where can I go about finding a 385 that I can modify? They seem nearly impossible to find nowadays
They come up on Ebay from time to time, A.L., or you could keep an eye on Craigslist for old projectors being offered for sale......usually cheap :)
Doug!! The lock washers under the machine nuts on the face of the amp are sending my OCD out of control!!
I'm not sure if that's good or bad, MD, but I tend to put lock washers under nuts to keep them from unscrewing. One might be a little off center......so I'll correct it :)
Lol, I asked about the NE-2 bulb on your previous video and you answered it here. I just finished this project myself. I thought it was drawing a little too much current and I used a 470 ohm resistor to bias the 6v6’s. It brought down the current but the plate voltage went up about 30V. Seems ok since the plate dissipation is around 11W for both tubes. Was I wrong about changing the cathode resistor or is that an ok mod?
It's the only way to alter the bias, TN, so you were wise to do so. The PC and PV are inversely related, so when one goes up, the other always goes down.
@@UncleDoug this was an awesome project. It’s about the closest I can get to a vintage amp without spending upwards of $2k that I don’t have.
@@t.nieblas2679 That's what makes these conversion amps so appealing, TN......great tone at a low price.
@@UncleDoug I see. That inverse relationship did surprise me since I’m used to just looking at ohms law where voltage and current are directly proportional.
@@t.nieblas2679 I believe they are always inversely proportional, TN. The moment current starts to flow, the pressure (voltage) diminishes.
Fitting that trem in that cramped chassis was a coup. Did you figure out why it was unstable?
It's been a while since I built it, Allan, but as I recall, it was eventually straightened out. I honestly don't remember the details.
Great video, UD! My 385 didn't have the speaker jacks labeled, don't remember how I determined 8 and 16ohm, have to look at. Mine is definitely dull with the NFB like you say. Also, mine hisses (not hums) really loud when you turn up the tone to the treble side. I removed the photocell which caused hiss originally. Any ideas there? Does yours have anything like the low-end thump of a Princeton Reverb now? That's what I'd like to shoot for. Thanks!
Hiss has not been an issue on mine, so I have no experience eliminating it. Generally, the cause is carbon comp resistors.....so you might change them out for metal film resistors. With the NFB turned down and a proper speaker in a good enclosure, I feel that the bass response is quite good.
Thanks much! Probably a winter project for me, really a novice at this point, but your vids are helping! Not sure if I asked you this before, but do you do conversions for other people?
Rusty and I have retired from doing outside work, Bill. Now we just focus on our hobbies and making videos.
OK. thought so but wasn't sure. Great work and videos for sure! Please tell Rusty the same for me ; )
I will, Bill. Thanks :)
I have a cabinet I built for a bell & Howell the version without a power transformer . I decided to scrap the project in favor of a amp with a pt anyway I really enjoy your videos and would like to give it to you it's just the shell very compact and unfinished but it's a really good head start really tight box joints I will try and private message you
Thanks, Jim. I responded to your Facebook posting.
I expected that old projector amp would come alive and it certainly did. There's a nice fullness to the sound that I prefer over the 5F1\5F2. Whats that green monster behind the 36? Your shop looks like an interesting place to spend the afternoon but I think I might need need some type of alcohol based liquid cooling to deal with those 111F temps. I thought 97 was bad here in the south. It's not even July. WOW!! Thank you again for another informative video.
Thanks, Sluggo. The vehicle under the tarp is a really nice 1952 Chevy pickup that I've been working on. I try to shield it from the sun, but it's a waste of time.....much like trying to shield a pine tree during a forest fire. The other day while working on it, if I set a tool down in the sun for more than a few seconds, it quickly became too hot to touch. I had to quit, put on some gloves, and then carry the tools into the "shade" to cool down.....to 110.
I would think that in the dual 8 ohm jack version, it was used to drive two speakers, one on each side of the 16 mm screen on
a gym stage where more coverage was necessary, Rat's nest wiring technique from the original factory build.
Good effort with all your improvements but to me it is not what I would call an inspiring amp if I had to play my guitar through it.
Those 283 Chevys were neat engines. With a 4 barrel you could get good performance from it. Nice little truck.
Thanks for all your comments, SC. Rusty and I always appreciate them.
I've read that the Canadian guy you refer to who popularized modding these vintage B&H amps - Bernie Rausig - reportedly modeled the tone stack of his builds after that of a vintage early '60s Vox AC-15. Does your build follow that lead or did you leave the tone circuit stock?
I left it alone, RF, and have honestly never felt the need to improve or alter it in any way.
I love that you added tremolo. I've always wanted one of these Filmosound amps but the lack of tremolo held me back as it has become the effect I use more than any other. If you ever decide to sell, let me know. I just may be your Huckleberry. Thanks for a great video.
By coincidence, I was working on it yesterday. The tremolo has developed a thump, which is very common.......but I don't like it and am going to try to eliminate it or at least reduce it quite a bit. If I can, the amp would be for sale. Other than the "thump" it works and sounds great.
Well, I'd definitely be interested if you get the Tremolo tamed, or at least close to the vibro champ feel you were working toward. Let me know.
I will, RF. Thanks for your interest in the amp.
thanks uncle doug.this gave me a few ideas for a pre amp based on a pas3. :-)
i really enjoy the vids.say hi to rusty and jack for me.
You're welcome, Gizmo. Rusty and Jack say "Hi" :)
The NFB is not the bad part of the tone. Austen hooks leaves his in. More to do with voltage and swapping ip.coupling caps and other parts for hid atleast. He uses 15k NFB resistor
Great little amp Doug. That tremolo sounds sweet. A little bit of the old switcheroo and this baby sounds good. Oh, and the Chevy is really tits.
Carl
Thanks so much, Carl. Glad you liked the amp and the old truck.
A beautiful sounding tremolo but it is definitely missing some nice knobs!
I couldn't find any suitable, small diameter knobs in my stash, PoB. I guess I'll have to add them to my shopping list for Antique Electronic Supply.
Nice job Doug. Talk about 10 pounds of stuff in a 5 pound box.
Hey, what are you using for the black-goo insulation blobs on those solder joints?
Thanks, Craig. Yes, it is a densely wired little rascal. I used black silicon gasket sealer, just in case the chassis was used with a metal base plate and one of the joints drooped a little.
I just watched this series again because you are careful to match the tubes and adjust the bias. My question is about tube swapping. There are currently many headphone and hi-fi tube amps being sold. (I like the resurgence of the tube circuits)
I am, however, somewhat mystified by some of the practices being professed. Many of these new amps are being marketed as having the ability to swap tubes out willy-nilly. If you want to change try another type of tube, just pull and plug. I have asked the sellers about setting bias and/or matching but have general received the answer that it is not necessary. I would have thought that making adjustments would be more important for hi-fi/headphone amps. Are these new amps immune to such needs because of some sort of magic tube fairy dust? Or will the modders be met with the possibility of premature tube/circuit failure due to the imbalance of it all? Sorry if OT, I didn't know of a better place to ask my noobish questions. Thanks.
Greetings, CK. Cathode biased output tubes tend to be "self-regulating" with regard to plate current, and this ability generally allows you to change tubes in such circuits without having to re-bias after each exchange. I assume that the amps you speak of are all cathode biased. This makes for a good sales pitch, but in my opinion, it never hurts to double check the bias from time to time. Bias resistor values can vary with use, and some of the newer tubes operate at voltage and current levels that may differ so greatly from those for which the original bias was set, that you really need to take occasional measurements to be sure everything is OK.
FIRST!! Thanks as always there Uncle Dougie!
You're welcome, Chout :)
Does anyone have a good link for a the M1 and M2 schematics for these? Nice video, thanks Uncle Doug!
I just added links to schematics in the video description, BMR. Here they are, I hope they are adequate: app.box.com/s/66hevc3qk0cqju83w1zpbozypyfgbfvu and app.box.com/s/3h56lk7ma36qomyscxgs5eojmhb8xd1t
Jack and Rusty did a fine job with that amp Doug!She really came out sweet so far, I'm quite impressed my man *thumbs*There is a neat old Filmosound sitting here waiting on a conversion, however she has a LOT more room inside.Would you like to see?How do I send you an image, you might like this one?John
Thanks, John. When they wake up for breakfast (around 11AM) I will let them know :) You are welcome to post photos on my Facebook page: Uncle Doug's Vintage Amps.
I'm still having trouble with the noise level. Otherwise great sound from this amp. Still need to change the 7851 and 5Y3 tubes to see if they're the cause. Seems to be a regular complaint on a lot of forums. Anything else I should try?
Learning a lot from your great vid's. Thanks.
Noise elimination is a complex issue, not easily diagnosed long distance, Vincent. I think you should focus on lead dress, bad connections, carbon comp resistors, etc. Good luck.
Having two of these amps sitting on my bench, I was very pleased to see you embark on this filmosound project amp. It was indeed a difficult project for an newbie like myself. With your youtube assistance I was able to follow your instructions and get through it. I did not add the tremolo (one must know their limitations) but now have an amp for some closet harp playing. Thank you.
Couple of Q's. I assume I don't need the 20 mf cap that's part of the oscillator circuit and do I need to replace all of the small caps to rid it of the hum I still have even after replacing the can electrolytics? I also noticed that you have a 33 mf cap in use and wondering what that was for?
"Like an old married couple ........" loved that part. Lol :-)
Greetings and congratulations on a successful conversion, Vincent. No, you don't need the oscillator cap, nor do you need to replace the smaller caps to reduce hum.....it generally won't help. You should focus on lead dress and the tubes themselves to see if they are the cause. I don't recall the 33uf cap......perhaps it was the closest value I had on hand (?)
Uncle Doug where do I find the flush mount pilot light? Nice work!!
As I recall, it came from Radio Shack. If they are still in business in your area, Pete, they generally have a nice selection of such bulbs and lights.
Thanks Doug! found the last Radio shack in my area going out of business sale the other day and got a nice flush mount pilot light. I'm working with the M-2 385. How would the pot work for the NFB issue? Since there's only one winding on the secondary where would the feedback resistor and pot be place?
Greatest sounds!
the truck is your new guitar amplifier project? sorry, just kidding ;)
pretty cool too.
about the project... crazy!
Perhaps you are the amplifier magician?
Thanks, Humberto :)