Peavey Triple XXX and the evil Tone-Stack

Tube or solid-state, this section goes to eleven!
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Post by 95H »


I need some advice to understand a few things about the Tone Stack, Crunch & Ultra, in the upper right corner of the schem.

So far I understand is this an active Tone-Stack with negative Feedback.

Main Problem is, the Amp is very gainy and harsch an fizzy and the Tone-Stack behaves strange and is hard to handle.

Is there any chance to get this zu a "normal" behavior such like a passive Tone-Stack?

What about reducing the negative Feedback by a Pot/Trimmer or Resistor? Don't want to make big changes to the circuit itself an values of the components if possible.
XXX Preamp.jpg
Other things to reduce the Gain I want to play around is:

[*]Changing R11, R7 Plateresistor from 150k to 100k
[*]Removing C19, C20 Kathode Bridge Cap, or lower the value - as well maybe the C24 in the first stage.
[*]Circuit around Diodes CR1,CR2, there are different opinions about, if Clipping-Stage or kind a Noise-Gate. Maybe take em out an listen what happens?
[*]Change R23 68K Slope to 100K, Clean Chan EQ

There are some suggestions about changes for the Poweramp as well, which I found flying around the Internet.
First of all I will change 6L6 to EL34

[*]Screen-grid resistor R101-R102 R117-R118 change from 100 ohm 5W to 1k 5W
[*]Remove CR-100 & CR-103 protection diode
[*]Change LTPI Resistors R108 & R111 to 1Meg and "bridge out" R106 Gridblocker - whole thing looks strange to me anyway.

Thanks in advance, I hope you have some Information to help this Monster to a less harsch voice.

Greetz from Berlin.

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