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Hi everyone,

I got a problem with my plexi V6. It seems that my sound is not very good. I got a bad distortion if i push the gain all the way up. And even when the gain is not so high, the sound is not great. And the tone stack don't seem to have great influence on the sound. The other channel exibit similar distortion. Same thing if i switch the EL84 Tubes or the 6V6 ones.

I have tried the amp with another speaker cab, same problem. I have substituted the tubes one at a time, same thing. The only tube I haven't changed is the EZ81 for the lack of spare.

When I first build the amp, i made a mistake and inverted R15 470 ohms and R18 470K ohms. Apparently it didn't seem to have burn some component. Since then, I have verified all component to be at their right place.

Any idea where i should check ?

The voltage seem a little low but i am not sure.

Mains 118 VAC
B+ before VRM 337
B+ after VRM 335

V1 (Tung-Sol 12AX7)
pin1 138
pin3 0.86
pin6 138
pin8 0.88

V2 (Tung-Sol 12AX7)
pin1 148
pin3 1.12
pin6 243
pin8 149

V3 (Tung-Sol 12AX7)
pin1 183
pin2 53
pin3 81
pin6 182
pin7 54
pin8 81

V4 (TAD EL84) (When selected)
pin3 12
pin7 322
pin9 308

V5 (TAD EL84)
pin3 12
pin7 320
pin9 308

V6 (RFT EZ-81)
pin1 288
pin3 335
pin7 288

V7 (TUNG-SOL 6V6GT) (When selected)
pin3 322
pin4 315
pin5 .147
Pin6 .147
Pin8 20

V8 (TUNG-SOL 6V6GT) (When selected)
pin3 322
pin4 315
pin5 .260
Pin6 .260
Pin8 20

Thanks for your suggestions.

Something is wrong with V2's cathode (#8).

Is that a reading error? Check your cathode resistor there as well as the cathode resistors ground.

Are you sure ?

In his documentation page 38 Stephen specify these voltage for the plexi v6

V2
Pin1 180 i got 148
Pin3 1.5 i got 1.12 (forgot to mention Clean Boost engaged)
Pin6 272 i got 243
Pin8 180 i got 149 (56k resistor + Tone Stack in the middle)

Which cathode do you think is the problem ? Pin3 or Pin8 ?

Forgot to mention in previous post. Clean Boost switch engaged and All the pots are in the middle except for the VRM which is full throttle.

Thank you

My bad, didn't see it was a cathode follower, that is fine then.

Ok,

Must be more complicated than I thought.

Well, I will unsolder all the component and verify each one separately.

I'll keep you posted.

Thank you