P12 causing component transformer hum

Hi all

Trying to track this down ; new p12 delivered a couple of days ago, it’s been in the rack but not connected.

I connected everything late today with my Holo May is connected to port 1; sadly the may is physically humming when connected to the p12 yet silent when direct to the wall.

I’ve tried removing ever cable from the may except for the power cable but the hum remains whenever the may is connected to the p12.

I’ve tried changing the settings, sine/multi, highlow distortion, without success.

Voltage is set to 240v as I’m based in Australia.

This wasn’t an issue with the p3 that the p12 is replacing.

Any ideas? Did I receive a dud?



I was getting transformer hum at my amp when connected to the P12 to the point I was going to return it. In my case switching from sine to MW 3 eliminated the hum. The hum is still present but minimized on MW 1/2

Which outlets on the P12 are you using for the May?

Sorry, not much help…



I’m using the first port for the may.

Each other port has its own item connected as I only have 4 devices all up.


If you mean the high current receptacle or zone D, try plugging the May into on of the other receptacles, see if that helps

Thanks John.

Tried without success.

I’m currently running this from the a port and also tried the b.


At one point I had two P20s and they caused egregious humming in my monoblocks. Same scenario you experienced- quiet when plugged into the wall, very loud buzzing when plugged into the power plant. My assessment of the situation was that the Power Plant regeneration was adding a DC offset during the conversion. Do yourself a quick favor and google ‘DC offset transformer hum’, there is quite extensive documentation out there.

PS audio used to manufacture a device to combat this exact issue called the Humbuster:

To solve my problem I added Emotiva’s solution after the Power Plant and it completely resolved the transformer hum for me:



Thankyou Tony,

I have tried using a Holton DC blocker between the P12 and the May as well as on the line feeding the P12 without success.


Oh man, that’s certainly a head scratcher. Probably a long shot but it never hurts to have a sanity check to confirm that the Holton is doing it job.

I hope you find a solution!

Have you called PS Audio service?

I’ve reached out to the local dealer who is going to get in touch with Ps audio.

Please make sure you post when you have come to a resolution (whatever that might be).

Just circling back on this one.

I am no closer to a solution.

Ps audio support have remoted into the device (didn’t know this was possible) and said it’s looking good from their side.

The local dealer has said that sometimes the incoming power can be so bad that the power plant struggles and suggested a dedicated line.

The line is going within the fortnight but I doubt this will change anything.

If the equipment is still humming after the dedicated line my dealer has offered to swap the unit for a new one however I still have my doubts as a misbehaving p12 would have been apparent to ps audio support when they remoted in.

Will report back

FWIW, if the Holo May is the ONLY connected component that hums, and it hums no mater which P12 outlet you connect it to, I am not sure you can be sure the issue is with the P12.

I can’t explain your scenario, but my gut tells me you have probably not yet eliminated other potential sources of the hum.

Good luck in any event.