Roadster EFX Loop tube???

[groovebelly]

Which 12ax7 is the EFX loop tube???

I'm getting waxing and waning volume in any channel that has the EFX loop engaged and am thinking this sounds like a tube...???

 

[espboogie123]

v1 Input stage/2nd stage
v2 3rd gain stage
v3 4th gain stage/tone stack driver
v4 reverb
v5 effects loop
v6 phase inverter

 

[groovebelly]

thx,
I'll change v5 out and see what happens!