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Phil Allison[_4_] Phil Allison[_4_] is offline
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Default Distortion please...Amp Distortion

Xtrchessreal wrote:

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I have a DIY amp built to Marshall 2204 circuit specs that is about 15 years old now. I use it at my gigs. I want to experiment a bit.

A couple ideas I have barely researched but have in mind:

Add a post PI volume pot - Without seeing a schematic I believe this would allow clipping in the PI while attenuating the AC signal from the output tubes without affecting the negative bias.



** Easy way to do this is with a single, log pot wired between the EL34 grids.

The pot should be about 500kohms, log taper and wired as a simple rheostat.



Attenuating the NFB - Simply adding a pot to do this seems easy but I know there are risks with oscillations.


** I wouldn't bother, Marshalls have low enough NFB as is.

Reducing NFB does not usually cause oscillations - increasing it does.


I wonder what other mods I could play around with to achieve some amp distortion? I have room to add more preamp valves.



** Beware of that idea.

Pedals are your friends.



..... Phil