Vox AC10 SRT

[MacGwyn]

Converting a Marshall 18 watt to a Vox AC10 SRT, but without vibrato and reverb.  What should I do with R16 and 17 that connect to the vibrato circuit?  Most amps have grid resistors in the same spot, but with a ground connection in between the two.  They bridge across the two phases between the PI and EL84 grids.  Any ideas on resistor values if they should stay in that position?  Is a ground between the two necessary?

[MacGwyn]

BTW, the values on the schematic are 220k resistors connected to the wiper on the vibrato depth pot... it's hard to read.

[sluckey]

We need to see a better picture.

[PRR]

> Is a ground between the two necessary?

In this case, YES.

And PLEASE give reasonable size pictures showing most of the circuit. I just had eye work.

[kagliostro]

Franco

[MacGwyn]

Thanks for the pic Kagliostro.  So far, I've tried 220k and 470k resistors (with ground between the two) between the PI output and EL84 grids.  In both cases, I'm getting only a very low level signal out of the speaker.  Sounds good, just WAY too soft in volume.  I'm going to go back through from the input, point by point checking connections.

[MacGwyn]

Got her up and running!     Eliminated a middle gain stage that was overloading something... probably the PI.  I included a gain stage where the reverb would have gone in the original, thinking there would be a need to overcome loss after the tone control - but it wasn't necessary.  Now using just half of V1, 12AX7 (single input) straight into the volume/tone and out to the first half of V2, the 12AU7.  Second half of that tube is the cathodyne PI.  I see why people rave about this rare bird online... it's gainy, but very balanced in tone.  Tone control is also useful, which I find kinda' rare for a single knob.  Vox AC-10 SRT... Recommended - it's a fun little amp.