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In Reply to: RE: Carver Tracking Power Supply posted by Alex M on May 1, 2025 at 05:59:23:
The 'sustained plateau bias' worked nicely in my baby Krell KSA-50S. This allowed the amp to run in true Class A mode while the music was playing but 'release' the high bias after a period of time so the amp would idle cool.I did some basic tests to verify by measuring how much power the Krell KSA-50S would draw from the AC mains. In a typical Class A amp the power draw could be hundreds of watts continuous at idle even if there is no music playing. The Class A amp would draw those hundreds of watts and bake for hours with or without music. This was the case with my small Pass Labs Aleph 3 amp. It consumed over 200-Watts just sitting there doing nothing except to heat up the room and run up the electric bill. And I would dare not leave it powered ON over night or longer unattended.
I don't remember the exact figures but sitting idle the Krell's power draw was fairly low and the amp sat cool. But crank up the music and the amp would draw several hundred watts sustained. Meaning it would go into high-bias Class A operation and stay there for 15 seconds or so even after the music stopped.
It was a little more complex than this because there were incrementally higher 'plateaus' of 'sustained bias' that the amp would increase to as the music demanded.... and then step down to a lower 'plateau' after about 15 seconds if the musical demand was no longer there. So instead of 'sliding' it 'stepped' in discrete increments. But make no mistake, those increments biased the Krell into true Class A operation as witnessed by the extreme heat and power draw from the AC mains. But once the music stopped completely you could leave the amp turned ON and it would idle cool.
I think this is different than the Carver amps.
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Follow Ups
- RE: Carver Tracking Power Supply - AbeCollins 05/1/2508:24:15 05/1/25 (0)
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