I recently bought a used Ampeg SVT3Pro. I had some problems with fuzz at low volumes, and after reading every post concerning this problem I came to the conclusion I had a problem with the bias setting. I noticed almost nobody adressed this common problem with the 3Pro in detail, hence my question. I measured the voltage over the "flameproof" resistors in the poweramp-section, they all were around 1mV. I read the biascurrent can't be higher than 20-25mA per mosfet (equals +/-10mV measured at the resistors), so I've set the bias to a higher setting, carefully checking not to exceed 10mV. The fuzz is gone now. The highest voltage is at 8.6mV (18.3mA), but all the others are way below this (the lowest around 1.7mV). Since none of the MOSFETs draws the same current, is there an optimal setting for the bias, or is the current current setting, with only one or two mosfets approaching 20mA, good enough? I don't have an osciloscope, just a simple multimeter.