Problem with P600


I have an original p600 power plant that I have had since they first came out. It has multiwave I.

Yeah, I know, old school.

I recently acquired a new dac that I plugged in last night. The dac transformer is exhibiting mechanical ringing and buzzing.

This is in sin mode.

I am very familiar with the mechanical sound some equipment makes when run in multiwave modes. This is different.

It starts out as a low ring that gets louder and becomes a buzz and then stops and regular low hum is left. After anywhere from 5-15 seconds later, the cycle begins again with low ring then buzzing. This cycle repeats over and over.

It is almost as if the charge/discharge of p600 caps are passing through.

I have plugged the dac directly into wall with same power cord and get normal transformer low level hum.

The dac seems to sounds fine (i have not yet become familiar with its character), but, from what I have read, transformer ringing is not good.

Any ideas?



The only thing that comes to mind is to try different voltage settings.


Never thought of changing the voltage, but, the unit was running at default 117v.

It kinda surprised me when I heard the ringing, and shut everything down.

I have taken it out of service until I can verify that nothing is wrong with it.

Of possible interest also is that I had a vintage equalizer I had just purchased plugged into PP which blew a channel after 15 mins of being plugged into it. Not saying the PP was the cause, but, it makes you wonder.

Also, I have used the PP for years with tube monoblocks and never noticed any constrained dynamics (I was around 400 watts consumed power on PP.)

I recently got a new tube integrated amp that seems constrained at 220 consumed watts. Again no definite sign of an issue, but, makes you wonder.

Hopefully (or not hopefully :wink: ) someone has experienced something like this and can relay their findings.


Something is definitely wrong here. It is as if the PP is out of sync with itself. I say the EQ problem was a warning shot.


My understanding is mechanical transformer hum can result from DC on the line. Maybe the P600 is putting out some DC for some reason (I used to own a P600 but never experienced anything like this).


Thanks everyone…hopefully Paul can chime in. I opened a ticket with them and will wait for response.


Is there any possibility you have access to a voltmeter? The older Power Plants can, after some time, lose their power supply capacitance and one side of them can get low. If this happens, they won;t output a true 120 volts, it’ll be more like 80 or so. If this happens, it will definitely need to come home for repair.