Second channel had this mysterious hum, that sounded to me like a ground loop. Shawn and I spent two hours trading out nearly every part of the bad channel with the good channel in frustration and then, finally, I realized that one of the three traces I was supposed to cut on the power supply PC board in order to mod it for this application was not cut and hence causing - you guessed it - a ground loop. Palm print on forehead. Before we left tonight we got it fixed and fired up both channels, playing some our favorite vinyl demo tracks with the Tube Phono and active step up prototype.
Holy s**t! It's not just a bigger badder lower midrange as one would expect. The bass is big and bad too, the midrange resolution is crazy good and it's like the power output of the system has gone up maybe a factor of 10. This is a keeper, and a very satisfying result of my spending the last year or so trying to come up with the ultimate version of my "low output impedance/no transformers/no cathode followers" line stage. Thanks to PJ for putting up with my theories over the past year and cooking up circuits based upon them, including this one.
You guys who have Paramounts, start saving your pennies. This circuit is a match made in heaven.
