I miss the telefunkin el34's of 30 years ago my marshall 's really came alive the new reissue tubes are not made in germany and not the same thing nor are the mullards the same bo hoo.
Another great video ! I'm lucky enough to have a great tech that is also an electronic engineer and every time I bring him a Marshall , it always gets back better quieter. I phone him back and say what the heck did you do ? He says , I fixed Marshall mistakes ! You remind me of him in a knowledgeable and intelligent way .
I have to admit, the intro was pretty awesome... the reverb was a nice touch. ;) Utterly fascinating dissection of this mod and the consequences of how it was done.
One of the most bizarre things to me about Marshall circuits (which I love) are the 250 or 320/330 uF cathode bypass caps on V1(a). So many frequencies are being amplified that are unnecessary, especially below 80 Hz or so. What value cap would you put there for a good, normal channel Marshall clean?
This is great! I owned a 1959RR, noisy as it could be. I had to reach out to Marshall and Jam Industries had me send it to a service center where they rebuilt the hum balance. Sounded much better after that, but still a wild animal of an amp and tough to tame.
Lyle that intro is an instant classic! You have listened to the amp hype channels! And then straight into a level headed breakdown of the circuit, fantastic! Click BAIT then switch!
About to handwire a 1987 in an origin 50 donor. So this was very helpful ! Great stuff as usual. I want to use the one wire mod and this made it clear. I looked at the robinette page and it was done differently and left me with questions...
This is great, very interesting stuff! Appreciate you sharing your knowledge. I built an amp about 10yrs ago. It was going to be a 1959 preamp with a 5watt 6V6 power amp. But I decided to go for a JCM800 preamp for a higher gain sound. Somewhere along the lines I got the two mixed up. It looks like a It has the same first stage as a JCM800 with the 2.7k/0.68u, or you could call it a 1959 bright channel. and the second stage is the jcm800 cold clipper with the 10k unbypassed cathode resistor, 22n on the output into a 470k/470k attenuator and the 3rd stage is the 820R/100k. What I can't figure out is why the output from the first stage, is more like a 1959. It goes to the 22n, then to the 1M vol pot, then through a 470k res (bright cap removed). As the rest is a JCM800 schematic it should have gone from 22n into the 470k/470p, to the 1M pot and then to stage 2. It has a kinda plexi sound but eq balance is all wrong. I think I forgot I went for jcm800 and partially wired it as a 1959 lol
What are the 1k grid resistors? Is this something marshall did on these amps? And cant you lower the V1a cathode bypass cap by inserting a .68 on the tube socket? You will be stuck with the 820 resistor still. But this would lower some gain and bass from V1a. Also, if you plug into normal channel and the put a cable or just a jack into bright channel input low or high, you will get so much gain that you have to turn both down to 5.
Would u consider doing a second video regarding the guitar pickup loading with regards to a buffer? Most guitar players have a pedal board and I am curious how the calculations change after running thru a boss pedal for example
I have tried adding 1Mohm resistor from 3rd triode stage grid to ground, right after the paralleled 470pF 470k because it creates a real voltage divider with 470k to lower frequencies. It sometimes makes the sound better especially if the cathode bypass capacitors or coupling caps of the circuit are a bit too big. Of course it loads the earlier stage triode output a bit more too.
Great video as always. Interesting stuff about the effect loading has on pickups. I wired my Tele to '50's Gibson spec (tone pot wired to vol pot wiper) and found that I didn't need a treble-bleed to compensate for high end loss. I guessed this was due to the reduced load on the pickup when the volume pot was turned down
You mentioned a problem with the "faulty heater balance circuit" at the beginning of the video but as far as I can tell you never talked about it again.
@@PsionicAudio LoL, I will have to go and double check the schematics. Thanks for showing the one wire mod schematic, finally have something in print to compare to.
The biggest problem that I see is the "guitar volume" pot wiring. At low settings it will absolutely cause all sorts of tone suck. I suggest disconnecting the wiper from its existing configuration and connecting it to the grid of the input tube. That way, the guitar pickup will see the same impedance regardless of the pot's position.
That's not how it works. Unless you put in relays the ch 1 connection will always load down an instrument plugged into ch 2. Limitation of the one wire mod.
@@PsionicAudio My comments were based on your simplified schematic. I just looked at the full schematic and see what you mean. VR1 (volume 2) is very unusual. In retrospect, I would probably replace it with a ganged dual pot to allow the same functionality while presenting as constant impedance as possible to the guitar pickup. But then, that's substantially bigger than a 1 wire mod. I've even built JFET buffers on a small board to ensure high input impedance for situations like this.
Yes, I know about the discolored JJ EL34s. ;)
TADs on order.
I miss the telefunkin el34's of 30 years ago my marshall 's really came alive the new reissue tubes are not made in germany and not the same thing nor are the mullards the same bo hoo.
I love my boss katana, I always thought Randy Rhodes had a shit tone
more videos like this please! very well done.
Another great video ! I'm lucky enough to have a great tech that is also an electronic engineer and every time
I bring him a Marshall , it always gets back better quieter.
I phone him back and say what the heck did you do ?
He says , I fixed Marshall mistakes !
You remind me of him in a knowledgeable and intelligent way .
I have to admit, the intro was pretty awesome... the reverb was a nice touch. ;)
Utterly fascinating dissection of this mod and the consequences of how it was done.
One of the most bizarre things to me about Marshall circuits (which I love) are the 250 or 320/330 uF cathode bypass caps on V1(a). So many frequencies are being amplified that are unnecessary, especially below 80 Hz or so. What value cap would you put there for a good, normal channel Marshall clean?
In my own builds if I want full response 10-22uf suffices.
more videos like this please! very well done.
Damn, you totally lost me there. I'm glad I'm not building amplifiers :)
Whew, the opening frightened me at first , I shoulda known better 😎
This is great! I owned a 1959RR, noisy as it could be. I had to reach out to Marshall and Jam Industries had me send it to a service center where they rebuilt the hum balance. Sounded much better after that, but still a wild animal of an amp and tough to tame.
Is the follow up video posted? I'm having a hard time finding it, curious about the bright cap choice.
Thanks for the informative circuit analysis. Even thought I'm not a Marshall fan, the analysis and problem solving was inspiring.
I did LOL on the opening . Enjoyed this video biggly ( sorry had to ) Bravo .
Took me a long time to understand the signature RR version, but once figured out its a damn versatile amp.
Lyle that intro is an instant classic! You have listened to the amp hype channels! And then straight into a level headed breakdown of the circuit, fantastic! Click BAIT then switch!
It's always good to see clickbait techniques being dissembled and dismissed.
Awesome intro lol 😝
What's with the blue tape?
About to handwire a 1987 in an origin 50 donor. So this was very helpful ! Great stuff as usual.
I want to use the one wire mod and this made it clear.
I looked at the robinette page and it was done differently and left me with questions...
I'm interested in a video where you discuss what you would do if you were free to do as you like with this amplifier. Or a regular 1959 reissue.
This is great, very interesting stuff! Appreciate you sharing your knowledge.
I built an amp about 10yrs ago. It was going to be a 1959 preamp with a 5watt 6V6 power amp. But I decided to go for a JCM800 preamp for a higher gain sound.
Somewhere along the lines I got the two mixed up. It looks like a It has the same first stage as a JCM800 with the 2.7k/0.68u, or you could call it a 1959 bright channel. and the second stage is the jcm800 cold clipper with the 10k unbypassed cathode resistor, 22n on the output into a 470k/470k attenuator and the 3rd stage is the 820R/100k.
What I can't figure out is why the output from the first stage, is more like a 1959. It goes to the 22n, then to the 1M vol pot, then through a 470k res (bright cap removed). As the rest is a JCM800 schematic it should have gone from 22n into the 470k/470p, to the 1M pot and then to stage 2. It has a kinda plexi sound but eq balance is all wrong. I think I forgot I went for jcm800 and partially wired it as a 1959 lol
What are the 1k grid resistors? Is this something marshall did on these amps?
And cant you lower the V1a cathode bypass cap by inserting a .68 on the tube socket? You will be stuck with the 820 resistor still. But this would lower some gain and bass from V1a.
Also, if you plug into normal channel and the put a cable or just a jack into bright channel input low or high, you will get so much gain that you have to turn both down to 5.
Super interesting. Would this setup work well with a Tweed Bassman (5F6A) clone?
I am ignorant about electronics. Your channel is opening my eyes and understanding. Thanks you Sir.
Kind of re-kindled my joy of electronics as a puzzle.
One thing DOES exist in a vacuum here… Electrons! 😂
Would u consider doing a second video regarding the guitar pickup loading with regards to a buffer? Most guitar players have a pedal board and I am curious how the calculations change after running thru a boss pedal for example
I have tried adding 1Mohm resistor from 3rd triode stage grid to ground, right after the paralleled 470pF 470k because it creates a real voltage divider with 470k to lower frequencies. It sometimes makes the sound better especially if the cathode bypass capacitors or coupling caps of the circuit are a bit too big. Of course it loads the earlier stage triode output a bit more too.
The one wire mod is cool because it’s easy. It worked fine for early metal an hard rock. Versatile it is not.
Thanks again for the great videos!
That's way more than one wire mod but you do nice work
Learning is something (thanks to you) fun and making sense at the same time 😎👍
Thank you😎👍❤🖖
Thank you for your outstanding explanation
WTF, did you voice over this one?
Stop being so damned professional, you're making me look bad.
I don't have the Jason Statham mini-me vibe, so I have to rely on my voice. ;)
This is splendid. Thank you so much. 😊😊
Youre the man Lyle 🤘
Great vid mate, always learn something new.
I was not expecting that intro... amazing!
Great vid and great advice for all!!
That intro. lmao!
Intro!!! 🤣🤣
You and uncle Doug should team up. Lol. Both of you guys are fantastic
Thanks man..
Great video as always. Interesting stuff about the effect loading has on pickups. I wired my Tele to '50's Gibson spec (tone pot wired to vol pot wiper) and found that I didn't need a treble-bleed to compensate for high end loss. I guessed this was due to the reduced load on the pickup when the volume pot was turned down
50s Gibson style wiring isn't for everyone, but as far as I'm concerned, it's magical
I do it on all of my own guitars.
@@andrewgarcia3136
100%
I started using the ‘50s wiring scheme with volume pots around 560/570k a few years ago and it was eye (ear?) opening.
You mentioned a problem with the "faulty heater balance circuit" at the beginning of the video but as far as I can tell you never talked about it again.
th-cam.com/video/CqAD2y5feQU/w-d-xo.html
Have you ever worked on a diezel?
Yeah but it was just a bad pot.
How different is the one wire mod from the high impedance 4 gain stage channel of a JCM800?
I just spent 22 minutes telling you. ;)
@@PsionicAudio LoL, I will have to go and double check the schematics. Thanks for showing the one wire mod schematic, finally have something in print to compare to.
The biggest problem that I see is the "guitar volume" pot wiring. At low settings it will absolutely cause all sorts of tone suck. I suggest disconnecting the wiper from its existing configuration and connecting it to the grid of the input tube. That way, the guitar pickup will see the same impedance regardless of the pot's position.
That's not how it works. Unless you put in relays the ch 1 connection will always load down an instrument plugged into ch 2. Limitation of the one wire mod.
@@PsionicAudio My comments were based on your simplified schematic. I just looked at the full schematic and see what you mean. VR1 (volume 2) is very unusual. In retrospect, I would probably replace it with a ganged dual pot to allow the same functionality while presenting as constant impedance as possible to the guitar pickup. But then, that's substantially bigger than a 1 wire mod. I've even built JFET buffers on a small board to ensure high input impedance for situations like this.