UberTuber

[EBK]

I double checked my sat pot.  It appears to be properly connected and working as it should, other than not doing much for the sound.  Seems that maybe the signal is too low there still?  I might have to dig out my scope.  Is adjusting the plate voltage merely adjusting the headroom without touching the gain (is this what "starved plate" means)?  (Again, I wish I knew more about tubes....)

[EBK]

This weekend, fingers crossed, I hope to connect my scope and function generator to this circuit to see if I can confirm my suspicion that the output is too low for the saturation control to work (suggesting that the tube's gain is too low).  Will report back.  I'll also test with a higher voltage on plate 1.  Although I can get it to distort by pushing that plate voltage down, I really need the saturation control to do more that it currently does to justify the extra knob.   

[EBK]

Ok, here are some results of testing with my scope and waveform generator.
Input is a roughly 100mV_P-P triangle wave at 1kHz. 

Is that a reasonable amplitude for a guitar signal?

The scope is measuring the top of the saturation diodes. 



This is with drive maxed.  The output is 476mV_P-P, not enough for the diodes to conduct at any setting of the saturation control.  If the input is cranked up much higher, then the sat control works as expected.

I'd be interested in hearing what the signal is under these conditions with a different tube.

Are there any additional tests that you would be interested in seeing?