Mod Troubles !

[Valvehead]

Hey guys--Im tinkering with a Marshall project . Ive changed the preamp to drive the tone stack from V2 plate , instead of the usual V2 cathode.

Other than changing a lot around V1 / V2 , I have not touched anything after the slope resistor. Its the stock 2203 Marshall tone stack and pots . The amp sounds REALLY good by the way.


So the tone controls are acting really funky ....

The bass works perfect , the presence is fine.

The treble control doesnt do anything at all !

The mid now acts as the Treble control !

again, i havent touched that area of the circuit .

So what am I missing ? Is it nesecary to re-wire the stack with this style circuit ??

I will include a basic scem of what I have here:



http://img.photobucket.com/albums/v2...psd8a5a330.jpg

[tboy]

That doesn't look quite right; the left end of the treble cap should connect to the plate of V2.

[Valvehead]

just ran a jumper for that----Bingo ! controls work great now ----- THANKS

[Bruce / Mission Amps]

Supposed to look like this to make that work

[daz]

Supposed to look like this to make that work

I've never seen that. Shouldn't both .022's be on the other side of the slope?

[Bruce / Mission Amps]

I've never seen that. Shouldn't both .022's be on the other side of the slope?

DOH!! yes.

[daz]

DOH!! yes.

LOL! I knew you obviously know that, but just had to point out your drawing mistake so you could slap your forehead.

[J M Fahey]

What Bruce said in the last version.

[Valvehead]

The amp turned out........incredible.

If you ever want to try hot rodding a marshall style preamp.........try the plate driven stack. Wow