P20 causes transformer buzz in amps

With my Vandersteen M5-HPA’s connected to my P20, the power transformers in the amps make what I think is a mechanical buzzing that is louder than when the amps are plugged directly into the wall, in which case I’d say the buzzing sounds about typical as compared to the various amps I’ve had in my home. Plugged into the wall, I can’t hear the amps unless I’m within three to four feet. With the P20, I can hear them from my 10 feet away listening chair. It’s louder in any level of multiwave than sinewave mode. Both modes are louder than plugging into the wall directly. It matters not if I choose high regulation or low distortion, or change the phase setting. What also makes a difference is lowering the output voltage from 120, which matches the input voltage at my house, to say 115V. But 115V out of the P20 still causes louder buzzing than 120V out of the wall directly. THD in averages 4 to 6%, THD out about .1 to .2% as seen in the display. What is going on here? Is it magnetostriction? A small amount of DC getting introduced by the P20? Something else? Also, the P20’s own transformer buzzes a small amount, audible up close only. Is that buzzing causing a sympathetic or not buzzing?

THD in or THD out averages 4 to 6 percent?

THD in. I just updated my post.

Good news, it appears the P20 is functioning fine.

But there goes my one temporary hypothesis.

I have had this exact same issue and thoroughly documented my experience in this thread:

I have come to the conclusion that the P20 generates DC as part of its regeneration. The only way I could eliminate the hum in the large transformers of my amplifiers was to add a DC blocker after the regenerator (https://emotiva.com/products/cmx-2).

I loved the sound coming out of my speakers with the P20 connected. I preferred the sound of my amplifiers transformer when directly connected to the wall.

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I think a response from PS Audio is warranted concerning if the P20 does generate DC offset. If so, that is a serious design flaw and I would want to know if there are any steps that can be taken to mitigate it in the field.

Please see my last comment. Is it functioning as designed or does it have a design flaw?

I’m going to add another twist here. My Audio Research Ref 6 SE has a reduced transformer buzz on Multiwave, level 4, as compared to sine wave mode. But this is a very small buzz, barely audible unless my ear is on the top cover, so I don’t consider it to necessarily be a problem. I haven’t listened to the Ref 6 plugged into the wall for comparison. I just find it interesting that multi wave causes a lessening on the preamp but an increase on the amp buzz, as compared to sine wave.

Paul’s response addressed incoming DC but not outgoing DC post regeneration:

PS Audio support’s response was a shoulder shrug:

They sent me a new unit and claimed it was going to be vetted by their senior staff specifically for DC offset issues prior to shipment. Once received it exhibited the same behavior.

Reading through my old thread raised my blood pressure haha I wish you luck. I enjoyed the P20s in my system but couldn’t stomach the distressing sounds they induced in my amplifiers and was lucky enough to return them back to the dealer (when PSA had a dealer network in the USA).

I hope you find resolution.



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Use a P10 and my Ref 6 is deadly quiet on both sine wave and all multiwave settings.

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My Hegel H20 (AB type) power amp hums annoyingly when connected to the wall, but is almost silent when connected to my P15. I had a P20 on loan before I bought the P15, and the H20 had slightly more hum on the P20, and the P20 itself also hummed a bit, but not detectable while seated and listening to quiet music. My P15 is on the sine setting, not MW.

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Same issue with a P15 and an Hegel H20 (opposite behaviour from @Standahm1, but different country power network).

PS Audio told me that was not DC generation issue, and the Oscillator board was even replaced (no luck).

Despite this, the P15 really contributed to the overall system performance (on top of the greater protection). I kept it, with the Hegel H20 connected to a KECES BP-2400.

I really wanted to have all gear connected to the P15, but I guess this issue is more and more common, and with many different power amps. PS Audio should deeply investigate this.

I have since installed an AudioQuest Niagara 5000 just for use with my amps and subwoofers. Not only does it not cause my amps to buzz, it allows for much greater dynamics, firmer and more powerful bass than my P20, which does a good job with my upstream constant current sources. I have my amps, subs and speakers along one wall, and my sources behind me on the opposite wall, which is another reason I need separate power conditioning for the two.

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