The Amp Garage

A friend had Sovtek 6SL7's in his ampeg and they were the root cause of big hum. NOS resolved it.

The 2meg pot from the reverb output is not wired correctly in the scheme. Not sure if that was mentioned.

The Tweed switch will cause a loud "POP" unless the volume is down at that moment. A solution is to place a large value resistor across the 2 switch contacts. I forget what I use in my Vibro Champ's tweed switch mod. I suggest 1 or 2 meg. Much quieter pop that way and no noticeable reduction in the ...

I think interstage trannies "affect" the signal during clipping in a manner that tubes don't. Not sure of the technical difference nor if it sounds good or bad. Perhaps the "affect" cancels out when used as a PI. I've never read anyone who said they are looking for that "clipping interstage tranny t...

A LTPI will have more drive potential than a cathodine at the same supply voltage and input voltage. But supply and input voltage are both “adjustable” by design as alluded to. So a “strong” drive to the output tubes should be achievable via either approach when considering all the “adjustable” vari...

What are the heater voltages running?

I had a short microphonic wire in the reverb circuit of my SFDR. It would cause feedback and noise.

Audio amps use them to avoid a cap on the cathode. While a cap is taboo in that world it is not taboo in a guitar amp. I use one in a trem cathode to indicate speed on the front panel of an amp.

The meter places a small load. Very small but it's there.

Arcing is often just a bad tube. Temporarily removing the cathode cap will remove it as a possible cause (could be shorted.) Having it off will not change the idle performance. Only the potential volume output will be reduced somewhat.

The 425 will go lower when there is a 6v6 running. Check the cathode resistor and temporarily remove the cathode cap.

365-0-365 allegedly yields 420V on the plate. 320-0-320 allegedly 350V.

Showing a proper ground on the power cord connection makes sense for safety. Moving the fuse to the hot side of the switch, instead of on the original neutral, would also make sense for the same reason.

Touching a probe to both pin 2 & 3 on a 6v6 6L6 EL34.....Oops...

I just picked up 2 from the PDB18xGTR series. The body is small but I guess size doesn't matter?