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previous: stokes Someone once suggested placing it b... -- 12/28/1999 4:19 AM

Re: placement of a standby switch

12/28/1999 5:22 AM
Bruce	Re: placement of a standby switch I've seen it used by Pete Traynor many times in the old tube amps. Plus a few homebrew amps I've looked at. It works good and I can't think of any reason to not use it. Oops, I just thought of a reason when not to use it. If your amp uses a negative bias supply that also needs the center tap to get a ground reference, then when the center tap is grounded again, the power tubes will be supplied with it's B+ at the same time the bias supply is building up negative voltage. If the bias supply's raw AC voltage is taken before the rectifier, off the high voltage secondary, it means the power tubes will be running with no bias for a few seconds while charging the bias supply filter cap(s) through it's 100K to 150K current limiting voltage divder resistor. Hope that made sense to those that have not seen this. Bruce

12/28/1999 5:22 AM

Bruce

Re: placement of a standby switch

I've seen it used by Pete Traynor many times in the old tube amps.
Plus a few homebrew amps I've looked at.
It works good and I can't think of any reason to not use it.
Oops,
I just thought of a reason when not to use it.
If your amp uses a negative bias supply that also needs the center tap to get a ground reference, then when the center tap is grounded again, the power tubes will be supplied with it's B+ at the same time the bias supply is building up negative voltage.
If the bias supply's raw AC voltage is taken before the rectifier, off the high voltage secondary, it means the power tubes will be running with no bias for a few seconds while charging the bias supply filter cap(s) through it's 100K to 150K current limiting voltage divder resistor.
Hope that made sense to those that have not seen this.

Bruce