The Amp Garage

Thanks for your advice I appreciate that.

I’m working on a JCM-800 and I find that the bias voltage ranges from -58VDc to -42VDC. I have tried the EL-34’s that the amp came in with and a new set. I find with a new Marshall branded set if EL-34’s the maximum they will pull is 27mA. The bias circuit is incredibly simple. A diode, two resistor...

[Franchesca (Express "85") had Clarostat PC style pots throughout where both Ingrid (Express "92") and the Liverpool from Funks images have a mix of Clarostat, PEC and Mil-spec AB's but in similar layouts. The 1megs used for volume appear different than those used for treble etc. I would be interes...

Malou is a very interesting example. The pots themselves are a great source of consideration for me as they each appear to have been selected for a reason. Either that or they were just sourced from a box of various pots! I know that Marshall used the "hot shield" regularly in their cascaded amps i...

Did you try the vintage/fast switch. That reduces the output from the second stage. I tried a few of those sorts of things over the years. To be honest I can't remember exactly the values I played with in that spot but I did have a switch on it. I think I mostly put the preamp back to stock now... ...

Yes those photos were on Dave funks website maybe thunderfunk.com but cant seem to find it. Dave was a authorized Trainwreck repair shop and after ken passed Dave decided to spill the beans that he had built Trainwrecks for ken. Would send ken the chassis and ken would tweak them, serial them, head...

Interesting that Funk would have been involved in the Liverpool with the extra cap and 10 turn variable resistor. I wonder which amp that is and whether it is one of the more known or not. Also wonder if there was just a great deal of Mil-spec pots in stock for the Mids or if there was something ab...

Malou is a very interesting example. The pots themselves are a great source of consideration for me as they each appear to have been selected for a reason. Either that or they were just sourced from a box of various pots! I know that Marshall used the "hot shield" regularly in their cascaded amps i...

Did you try the vintage/fast switch. That reduces the output from the second stage.

One mod that doesn't get any love is the Maloo picture where there is a small ceramic cap in series with a ten turn pot across the 100K plate resistor of the second triode stage. It was for high output pickups, but I noticed (depending on the cap value) it can boost bass after the tone controls. I h...

Stevem wrote: ↑Wed Mar 27, 2024 9:53 am Give me your mailing address and I will send you a few!

I’m sure they will eventuate.

I have using it for a couple of days and I have yet to see a bad valve. I was wondering what is going on.

:evil: I agree that Ken had a standard circuit with given values and materials that were the basis of the amp models he developed. I also know that my 70 JMP50 doesn't sound the same am my 76 JMP50 even though they are the same circuits. I'm accepting that some of the components in each vary in thei...

I have been given a Knight 600 tester. I REALLY appreciate being given it, but I haven’t yet found it to be a meaningful tester, it is early days using it, but I thought I would put the question to the brains trust here and see if there are tips or tricks surrounding using the tester. https://youtu....

I think when he said there's no mojo, it's science, he meant there's no magic pixie dust .. so many silly things have been said about these amps and Ken was playing with people when he said things like red wire sounds better etc etc. It's in the design. Caps , resistors, layout. Not mojo or magic.....