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Peavey Triple XXX and the evil Tone-Stack

Posted: 08 Apr 2018, 08:41
by 95H
Hallo,

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.
Poweramp.jpg
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.

Re: Peavey Triple XXX and the evil Tone-Stack

Posted: 23 Jun 2020, 13:58
by EddieTavares
95H

First I suggest you to use a tubescreamer or another overdrive in the dirt channels, usually it give better dirt tones.

If you did but it was not enough, I suggest you to remove C8, the capacitor that bypasses R10 to reduce the gain and brightness. If it isn't enough you can reduce r21 and r17 by your taste.

Re: Peavey Triple XXX and the evil Tone-Stack

Posted: 05 Sep 2020, 22:24
by Jmpj48
You don’t want a passive tone stack in that amp. The active tone stack in that amp is awesome. If The tone stack is acting weird Something is wrong with it. That’s one of the best tone stacks around and amp. Designed by the legend James brown.

Re: Peavey Triple XXX and the evil Tone-Stack

Posted: 06 Sep 2020, 16:23
by bmxguitarsbmx
The Peavey Triple X is definitely a thrash amp. If you don't like its basic tone and the way the eq responds, maybe consider selling it to someone to whom fully embraces that sound.

The Peavey JSX is built on this platform. Look at that for some inspiration to get a better clean tone. The crunch and Ultra from the JSX may also be better than the XXX.

To remove fizz you can try increasing the B+ to the preamp section to get a little more headroom. 22k across R67 and 10k across R81 to de-fizz the preamp. Changing the 150k to 100k is probably a good idea. You could put a 470p-1n across that plate resistor as well.

CR1 and CR2 are a noise gate. Look at the JSX schematic to see a variable version of this noise gate. Putting a variable resistor or Shorting R3 will also remove fizz and make the tone much better, especially if you are after lower gain tones.

I don't like the active eq either, but it might be hard to convert. Check out the scheme for the Peavey Valveking. That amp sounds great! And can get cleans in the overdrive channel with the boost on if you short out the noise gate diodes. Part of why it sounds and feels better is the passive FMV tonestack. The edge is just a little spongier.

I hope that is helpful. I would still recommend selling it and trying to build your tone from something else. The Active EQ is a very aggressive sound even with everything half way up. And then again, that is why a lot of people love those amps!