Mike Here with an update... "Estate Sale Gems" (ESG)... I found some really killer NOS 12AU7 tubes at an estate sale. Super low noise and super warm fat tones. If you want to upgrade your purchase with an ESG tube, shoot me an email at email@example.com. There is an additional charge of $20 per tube. The tubes normally included with Soul Drives are tested on a tube tester and tested by ear for microphonics, but they are not screened for normal tube noise unless it seems higher than average. However, our ESG tubes go through more significant testing and are compared against other 12AU7 tubes to find those that exhibit less tube noise than average. I have developed a noise rating system (A+, A, A-, B+, B, B-). Any tube heard as a "B" or worse in terms of noise will always get rejected in any Soul Drive pedal. A- and B+ tubes are average NOS tubes. The ESG tubes are hand selected when they exhibit noise low enough to be considered A+ or A rated. ESG tubes are also fatter sounding in terms of tone, IMHO.
About the Author
Mike Congilosi II, Inventor/Engineer