Platinum Supporting Member
I know they did not bother with this 'back in the day', but is matching up power tubes less of a concern with cathode bias amps than with fixed bias?
The PI balance isn't really relevant. How mismatched are the power tubes? Anything within 5mA is more than close enough. Try switching positions and listening. If one way sounds better than the other that's the right positioning.I have a pair of 6L6 tubes that are slightly mismatched. The amp is a stock 65 Super Reverb. Considering that most phase inverter circuits do not produce perfectly balanced signals, which socket should I put the hotter tube in?
Think of it this way: You can use mis-matched tubes, IF...you set the bias for optimum performance from the tube drawing the highest current. Now you have one tube working well, and one ...not as well. The issue is when one tube is drawing too much current at whatever your cathode bias setting is and red-plates. Then, you have one happy tube, and one very feverish tube. That make sense?is matching up power tubes less of a concern with cathode bias amps than with fixed bias?
That's by far the best way forward - even quite miss-matched power tend to balance out with similar cathode currents with this arrangement.An option would be to split the bias and give each tube its own (different) cathode resistor/cap combo.
This is opinion and not techno-gospel, but IMO, matching tubes is even more important with a cathode biased amp than with adjustable fixed bias.No, same concerns as with fixed bias amps.