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In Reply to: RE: Power conditioners-Do they work? posted by anton90125 on September 21, 2007 at 02:28:22
The hum from AC-powered filaments of directly heated triodes or pentodes is benign if AC is purely sinusoidal. Unfortunately, with today's proliferation of capacitor input supplies and switching supplies power waveform is far from sinusoidal, which turns benign hum into annoying buzz. A conditioner that restores sinusoidal waveform is not just really helpful, it is a must with a DHT amp.
It is also important what is downstream of power conditioners. It makes little sense in conditioning power if one's equipment is a source of contamination. AFAIK, almost all commercial equipment uses power supplies that make noise. I haven't seen any that use "clean" choke input filters.
Follow Ups:
You are definitely right, replace those big electrolytic capacitors with some nice copper chokes and polypropylene film capacitors and the world is a much nicer place. The real "magic" of old tube gear isn't actually in the tubes, but the topology.
Hi.
But I tend to disagree that audio amps without the "clean choke input filers" bound to sound noisy.
c-J
There is solid engineering behind the advantages of choke input supply. Critical value choke preserves the sinusoidal waveform of transformer current, whereas capacitor input badly distorts it, creating high frequency noise. That is, exactly the noise that power conditioner is meant to alleviate.
One who uses power conditioner to feed equipment with swithing or cap input supply is like marquis De Sad who used to hand pick the most beautiful rose only to crush it into durt.
As to amps with inferior power supplies, they indeed don't sound noisy, they sound crappy.
Hi.
Let's check up the "Dynamic behaviour of PSU" report posted only yesterday in Tube DIY forum. An good ready-made technical reference.
Now take a close look at the the chart showing wave patterns of a choke of critical inductance 5H (page 3) vs that of a conventional C I/P PSU (page 5).
Regarding the obvious different voltage levels, the dynamic behavour of both PSUs as shown in their wave patterns were very similar, if not so deceivingly identical.
Ironically, they are both so dissimilar to the same choke I/P PSU using mercury vapour rectifiers.
IMO, the waveform pattern of the C I/P PSU is grossly smoother from attack to decay than the choke I/P PSU.
You want to comment on the report finding?
While sonics is so subjective, I am not in a postion to debate with you which type of I/P PSU should sound better to whoever.
Sorry, I don't find a adequate designed/built capacitor I/P PSU would sound "crappy".
c-J
It may be true that the downstream waveform is not different between the two, but what happens is that with a capacitor input power supply, the charging currents through the power transformer to charge that input cap are much greater. This causes the power transformer to radiate RFI like an antenna into the rest of the circuits of the amp. I think Allen Wright once said that by not implementing a choke input for your power supply, "that it is like hitting yourself in the head with a hammer."
If you do need the output voltage and therefore must implementa a capacitor input, use the smallest capacitor possible to deliver the voltage that you need.
Retsel
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