Express: Add gain pot and bypass switch for 3rd gain stage

[roseblood11]

Hello,

I need some help - I'm planning an amp, that's not exactly a Trainwreck Express clone, but it will have the same basic topology: Gain stage - Tone stack - gain stage - "cold clipper" gain stage - LTP - PP Power amp

The first two stages and the tonestack will be like the bright channel of a Fender 6g11 Vibrolux, Phase Inverter and Power Amp come from the 6g3 Deluxe (2*6V6 with GZ34 rectifier).
http://tubeamplifierparts.com/layouts/f ... layout.pdf
https://www.tedweber.com/media/kits/lenora_schem.jpg
So the "core" will be a typical Fender Brownface Amp, including the bias tremolo from the 6g3.

But I want to add the third gain stage from the Trainwreck Express, but with an extra gain pot (in front of the grid), and I need the option to bypass this stage (and the pot) with a switch

Has anybody built something similar, maybe just an added switch in a standard Express circuit?
I'm not sure how the switch would have to be wired. Is it possible to do it with only a spdt?

[roseblood11]

Will this work?
How will V3 influence the sound, when it's not in the signal chain? The grid is always connected...

triode bypass.jpg

[stiltamp]

If the grid of V3 becomes positiv due to a high signal peak, then the sound is influenced, because there is a current flow into the grid.
The current flow into the grid causes a voltage drop on the resitors R2 and R3.
If the S1 in the right switch position, the right pin of capacitor C3 is not connected and hangs in the air.
I recommend the modificaton as shown in the schematic as follows to prevent switching noise.

SchematicIdea.jpg