Bob Latino LTA ST120 OR QS MID MONO'S in Talkin' Tubes Posted January 16 · Edited January 16 by amped clarity 3 hours ago, xoundmind said: can you explain the workings of the auto bias function? How hands on? Here's the manual that came with the board. http://www.***.cz/files/AB-Q_ST-70_ST120_manual.pdf Once it's set to the desired bias voltage by the installer, there's no real hands on. Make sure they know what tubes you're using and clear it (voltage) with Bob. I was still checking my bias for a bit after installing but all 4 tubes were always the same (as designed). Hope this helps. Bob was/ is a pleasure to deal with as well.