Name:    Steve Kennedy
Email:   steve@pacair.com  
Subject: best wishes
Thread:  25
Time:    Mon, 17 Dec 2001 06:40:55 UTC

As a rule of thumb I generally just check to make sure that they set up for about 15mA of bias current at idle in high power.


On an older tube phase-splitter unit, this would equate to 150 mV across the 10 ohm 1 watt cathode resistors.


On the newer solid-state phase-splitter units a 3.9 ohm cathode resistor is used, so I would look for about 55 to 60 mV across these.


If everything is in order and you use matched tubes, the bias current as measured across all the cathode resistors should be pretty close to each other.


Does anyone here do it any differently? With the potential for over 700Vdc of plate voltage at the high power setting, it only seems right to limit the current to under 20mA.


These amps use about twice the plate voltage as other amp designs, so 1/2 the typical bias current should be in order if you want the tubes to last!


Steve