The Amp Garage

I have a variac but I recently picked up a "Brown Box". It is pricey for what it is but it is very well built and works well. As far as I can tell it's a bucking transformer, but it also has several input taps and reduces the voltage to more than the typical -6 or -12v that most bucking/filament tra...

The "1 meg" volume pot in my '85 Express measures pretty high at about 1.3meg wide open, but only measures about 80k on 1/2. This nets quite a range of control down in the end of the dial where most folks like to play these amps. I'm not sure if there are many "audio" or "log" taper pots made these ...

A few here, myself included, have changed to a 500K volume pot in the Express. Either way, 1M or 500K, I would never be turning that knob up to '10' but - IMO - the circuit syncs better with the 500K for my tastes. The hiss is nothing here, really. It exists in a certain band and it might be louder...

My originals run about 415v B+. My comparison with a JTM45 was an original 60s version, and I have a '70 JMP50 that measures out more like 65 watts clean. Still compare a wreck to an old 4 input Superlead 100 and the wreck will sound like a practice amp!

True these things are quite strong sounding. Still the best way to get cleans with these amps is to lower the guitar knobs. Also some audio taper pots come on quicker than others for sure. My '85 express volume pot is so smooth the amp is barely playing on 1/4, pretty rockin @ 1pm, but there is stil...

You might try a few different volume pots if it comes on too quickly. Try to find a log or analog taper pot with no more than a 10% taper. What I mean by 10% is a 1 Meg volume pot that only reads about 100k or even less on 1/2 volume. On my '85 Express the amp is still clean up to almost 1/3, by 1/2...

I think you still need to kill the noise at the sources, and leave the amp alone. I highly doubt grid stoppers are going to make much of a dent in the noise. The grid stoppers are sometimes added to reduce just a hint of high end response which can kill oscillations. By the time you use resistors bi...

I used to pick up AM radio now and then, but not since I started using Mogami cables.

Most likely it is your guitar picking up air born noise, from things such as light dimmers, florescent lighting, or other odd electronic items. The high gain (and hi frequency openness) of these amps makes noise pickup simply more problematic but even an old Plexi will do this if dimed. Still when y...

Thank you for the kinds words Shaunf! And your help was truly appreciated. When I mentioned the amp was quiet, I was refererring to the absence of Hum, buzzing, scratching VC and other nasties etc. Hiss is very evident when dimmed, but I would NEVER play this loud. I am also greatlful or "lucky" wi...

Sounds like it's healthy!

It should be about a little less noisy than a fully dimed 4 input lead spec Marshall IF you back the TW down to similar gain levels probably about 1/2 with the knobs depending on pot taper. If it is indeed really really quiet dimed, I'd actually suspect it is actually oscillating above the range of ...

Looking great! Good call on the needed Mosfet heatsink, or chassis mount for it. Perhaps you could mount the Mosfet close by and add short jumpers over to it? Or maybe a vertical heatsink right near the VVR board. Others will know better what is workable there. I have heard good things about the VVR...

Here is another observation of my original Express amps, regarding the [b]pots in the amps[/b] themselves. I had posted this on another forum but will copy it here. Point of my post was to mention that the amp gain itself can seem higher (in regard to typical knob position, if there is such a thing)...

What he said. I couldn't have said it better!
GK