David Nebenzahl wrote:
Geo spake thus:

On 15 Oct 2006 09:24:45 -0700, "

wrote:

For the BD's to heat up like this with literally no input signal,
shouldn't they have to conduct a large DC current instead?

Yes - if you have 0.5 volt across the resistor then there is 1 amp
flowing all
the time and with 50 volts available you are dissipating 50 watts
of heat.

Say what? My arithmetic gives me 1/2 watt (0.5 V @ 1 A).

Your arithmetic is correct for the resistors but that same 1 amp is
flowing throught the power transistors as well. Each of those has 25
volts (though I suspect it droops with that much load) so each
transistor drops 24.5 volts at 1 amp. 49 watts needs a pretty
significant heatsink. I would target the idle current at 20-50mA.

GG