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Standby Mode in Krell FPB power amps

When most large power amps are turned on, they draw a large surge current from the AC line for a second or two while the large power supply filter capacitors are charging, and then settle down to an idle current level. My question is:

When Krell FPB power amps (the 250M monoblocks specifically) are switched from ON to STANDBY, do the power supply capacitors remain charged, so that there is no large turn-on current the next time you switch back to ON (i.e., only a change from STANDBY current draw to idle current draw), or are the power supply capacitors discharged, so that there is a large current surge every time you switch back to ON?

I E-mailed Krell this question, but I haven't received a response from them as yet.

Thanks!
a_hayman
dky
9 posts
 
Standbye appears to be a soft turn on. When I flip the breaker at the back of the amp I do get the surge current. If I use the front panel button or remote the amp does not have this same surge. In standbye the amp is partially powered up and drawing current. I have had a FPB 200 and now I run a 400CX. Both amps turn on the same.
morbius396c
134 posts
 
A_hayman,

When the back panel circuit breaker is turned on, the power
supply and the input circuitry are energized. The amplification
stages are not powered.

When you push the front panel power button, the bias circuitry
is fired up [ lower left LED in front triangle turns on ].
The power regulator circuitry is then powered up, and when it
is up and providing power to the output stages, the lower
right LED lights. When the protection circuitry has checked
that amplifier operation is safe - no shorts... - the input
relays close - and the amp is ready for operation.

So you are correct that the power supply capacitors remain
charged as long as the back panel breaker is on.

Dr. Gregory Greenman
Physicist
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