the McGrath Mini amplifier

Well, I've transported the McGrath Mini down to San Diego, where I'm continuing the testing and burn-in process.  Also, I hope to make some playing videos, because for guitars I have not only my Squier Mini-Strat for the single-coil sounds, but also my lovely Carvin DC-200K, a humbucker guitar with Gibson scale length, i.e., about the closest approximation to a Les Paul that I'm likely to get any time soon (actually the Carvin is much better than a Les Paul IMO). Anyway.  In the testing arena, I continue to be pleased with how much the 10pF "degenerator" caps have improved stability.  It is still possible to get some pretty nasty self-oscillation out of her by turning up all the gains and maxing the mid and treble in the M-section, but it's at least less likely to happen at "reasonable" settings.  I still have some more shielding work to do, so maybe this will help. But the main outstanding problem I have noticed is that the v-mid EQ doesn't seem...

  I determined that the lower-than-expected fx loop gain was due to a wiring error: effectively, I was only running through one of the two gain stages on the return, so instead of a gain of 100, I had a gain of 10; given the send attenuation of 20:1, this led to an overall loop gain of 0.5, which was commensurate with the lower level I was hearing when the loop was engaged (-6dB). After fixing the wiring error so that both stages were operational, the gain (as expected) was too high.  Theoretically, the overall loop gain would have been 5, but my ears told me it wasn't quite that high (for complicated math reasons, the gain of these negative-feedback triode stages isn't quite as high as the simple resistor ratios would suggest; akin to how cathode followers have a true gain slightly less than 1).  Nonetheless, I first tried substituting a 1M resistor for the 4.7M feedback resistor in the second stage.  This should have theoretically resulted in a perfect gain of 20 o...