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Noise reduction.

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In Reply to: RE: The transformer participates in converting the diode pulses into noise. posted by tomsyl1 on May 27, 2008 at 13:15:16

Adding series filter elements in front of power amp supplies may harm the dynamics and counter any benefit from noise isolation. Chokes reflect noise energy, so if the transformer rings from the diode pulses, adding a common-mode choke may just intensify the ringing.

I don't have experience with bypassing HexFRED diodes, but I would use R-C snubber networks instead of simple capacitors. Ceramic caps are not good for the sound. The Wima metallized paper caps are good if you can meet the voltage requirements.

Tube rectifiers do not store charge, so they avoid the reverse current pulses altogether. In addition to the obvious drawbacks, keep in mind that there is finite cathode-heater capacitance. This is an unexpected pathway for noise through the heater winding of the power transformer.

Follow Ups:

RE: Noise reduction. - Ugly 15:10:18 05/28/08 (1)
- My experience is with AC filter caps. - Al Sekela 15:46:54 05/30/08 (0)
RE: Noise reduction. - tomsyl1 14:15:31 05/28/08 (2)
- Nope, not a "joelister." - Al Sekela 09:48:27 05/30/08 (1)
  - RE: Nope, not a "joelister." - tomsyl1 17:16:43 05/31/08 (0)

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