The Amp Garage

The Primary impedance of the OT on the spec sheet is 1.8k. It's the mojotone/heyboer "silver bells" "800/plexi style" transformer. By bias current, you mean the reading at pin 5? -36v, and I remember flipping the meter to mA, and getting 36mA, but it jumps around between 34-38. Last time I played th...

so I just took it to the studio, tried it out with a 4x12 cab with tonkers. Apparently, the attenuator is the problem. This amp doesnt seem to like it. I've tried the attenuator with a dozen other amps and never had problems. This particular amp, for some reason, hates it. Sounds great without it. W...

So here are some pics and a voltage chart. Worth nothing that when I try playing it cranked (through the attenuator) I can hear the power tubes cackling from the heat....despite my bias being set fairly low (think) Also, in the 15 min I had the amp on while taking the readings for this chart, I coul...

The amp sounds good when it's not driven. Not much of a difference with gain below 4 with or without an attenuator load on either channel unless I crank the presence to 10. Dial in anything past a slight crunch and it sounds like a really unhappy circuit. I can't crank it without a load or record it...

Nevermind that last troubleshoot, i just realized why that's a retarded question...

Ah...ok, thanks guys. I put in the fizz cap and it tamed some of the nastyness, but some still remains. If it's normal for the power tubes or output transformer to vibrate in sympathy with the signal at high power, is it also normal for this vibration to be modulated/increased by turning up the pres...

I just finished a DIY build of a 1959slp reproduction, and have run into a really weird issue I've never seen before in an amp. (then again, i'm not that experienced) I have it hooked up to a weber mass200 attenuator into a 15" speaker for testing on my bench. When I really dig in or have the volume...