Bypassing power supply electros

smithy666 · 22nd May 2007, 04:46 AM

Hi all
I have a few large (33000uF) caps I am using in a couple of power amps. Is it worthwhile bypassing these with small value polyprop caps (audible difference?)? If so, what values are recommended?
Thanks
Smithy

Conrad Hoffman · 22nd May 2007, 12:25 PM

Controversial subject. On the upside, it can't hurt anything. Polypropylene has great HF performance, so use as large as will fit easily. IMO, bypassing at the cap terminals is not the best place, if you hope to address the two things that matter. If you have RF from the bridge diodes, bypass at the diodes. If you need bypassing for the circuitry, bypass at the circuitry. IMO again, it's more important that the wiring at the caps be done correctly. That means bringing a stub off the ground strap and wiring the circuit grounds to that, so you don't pick up currents related to the rectifiers. Split the rectifier return and run it to the terminals directly, not to the same ground strap as the circuitry. The rectifier output should be wired to the terminals, and the power taken off another set of wires going to the terminals. Don't get any circuitry related wiring connected in the charging loop, or you'll get line frequency contamination. Hopefully I've described that correctly, but a better reference is Self's book on amp design.

22nd May 2007, 04:46 AM	#1
smithy666 diyAudio Member Join Date: Mar 2001 Location: Sydney	Bypassing power supply electros Hi all I have a few large (33000uF) caps I am using in a couple of power amps. Is it worthwhile bypassing these with small value polyprop caps (audible difference?)? If so, what values are recommended? Thanks Smithy

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22nd May 2007, 12:25 PM	#2
Conrad Hoffman diyAudio Member Join Date: Mar 2007 Location: Canandaigua, NY USA	Controversial subject. On the upside, it can't hurt anything. Polypropylene has great HF performance, so use as large as will fit easily. IMO, bypassing at the cap terminals is not the best place, if you hope to address the two things that matter. If you have RF from the bridge diodes, bypass at the diodes. If you need bypassing for the circuitry, bypass at the circuitry. IMO again, it's more important that the wiring at the caps be done correctly. That means bringing a stub off the ground strap and wiring the circuit grounds to that, so you don't pick up currents related to the rectifiers. Split the rectifier return and run it to the terminals directly, not to the same ground strap as the circuitry. The rectifier output should be wired to the terminals, and the power taken off another set of wires going to the terminals. Don't get any circuitry related wiring connected in the charging loop, or you'll get line frequency contamination. Hopefully I've described that correctly, but a better reference is Self's book on amp design.

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