The Amp Garage

imo1 wrote: ↑Thu May 30, 2024 2:54 pm I don’t have the specs but don’t el84s need a good deal less gain to drive them then 6v6s? That would make sense.

I believe you are correct & that EL84s do require less gain.


And I even made a mental note to that effect when I was mapping this out, but misplaced the note...or the dog ate it.

grid resistors also help minimizing blocking distortion. and be careful with .1uf coupling caps in the PI combined with 220k bias splitters On my project, I was able to experiment some yesterday with knocking back the PI input using a voltage divider (the 220K + an added 250K pot to ground) & made ...

Thank you both for the info & the markup. Looks like I need to fool with PI input voltage divider as implemented here. I have built nearly this exact circuit, including the dwell, SS rectifier & choke, with the exception of using EL84s & a few different resistor values in the PI because of the diffe...

Wondering if you have an updated final schematic?

I have a similar amp nearing completion, seems to have more gain than I expected or want. I would be interested to see where you ended up.

If the goal is to reduce output power, I'd leave the power section as-is, and add a master volume, which could be located in the extension speaker jack position. I did just that in a Bassman recently. Added a LarMar with the control on the back, in the EXT Speaker position. Works great, completely ...

So Just to clarify where you ended up, using 190K in place of the 330K on your original schematic addressed the issue?

A1Sensei wrote: ↑Fri Apr 05, 2024 11:23 pm I looked in back and the power tubes were all dark.

This seems like a problem.


If it were me, I would start here, looking for bad connections.

oxbow_lake wrote: ↑Mon Mar 11, 2024 2:47 amI get the impression that they really do want 400+V on the 12at7 (to maximize headroom? just to drive the tank hard enough?)

I recently built a Champ with a full 2-tube Fender reverb circuit + a dwell control. I am running +357V on the plates of the 12AT7 with more reverb than I can use.