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Transformer noise including Powervar

First, all transformers make acoustic noise. That is their nature. But the manufacturer should know how to limit or dampen these vibrations to keep them pretty much inaudible.

The transformer in a power conditioner or power amplifier will make audible noise for primarily one reason: improper AC input. All transformers require a constant specified voltage and frequency just like all other electronics. The AC input requirements are specified on the rear of the unit.

If one feeds the unit improper voltage or frequency, the magnetized plates in the core of the transformer do not operate properly and rattle…hence the noise. And this information comes from the chief engineer at Powervar.

Powervar and many other power conditioners do not regenerate the AC sine wave or regulate voltage or frequency. The AC that goes in comes out less AC TRANSIENTS and AC NOISE.

With that being said, there are many AC line sources that can cause transformer noise including DC on the mains. If you are interested in understanding what they are and becoming educated on the subject, I suggested highly that you read the following article and focus on section 3. “Adverse Mains Conditions”. Go to: http://www.plitron.com/PDF/AES.PDF The article is excellent.

So if you are going to use a Powervar, you should feed it proper AC sign wave. The AC can be full of transients and noise but it has to be the correct voltage and frequency. The Powervar will clean the transients and noise but it is not going to change the sine wave. One can only do that with a regenerator and that comes with a price of course.
drdokman1
palasr
453 posts
 
Try this:

http://diyparadise.com/dablok.html

to remove that pesky DC from your mains supply. Remember, only a few mV of DC can make toroids hum like there's no tomorrow. I used this same basic design when I built my DIY Armegeddon-clone power supply for my Linn, and it cut the mechanical noise in the 1:1 isolation toroid by about three quarters (yes, it's that effective). Check DIY Audio for the abundant debate on HOW this circuit actually works. Pretty spiffy if you ask me. Regards,

-Richard
sugarbrie
3,854 posts
 
Yeah, it is usually DC Offset that makes them hum. Blame your power company. They won't fix it, so you have to.
mdhoover
690 posts
 
This is quite helpful. I was planning to sell my Powervar, but may attempt a DC blocker instead. In layman's terms, how does one construct this blocker? Any pics of your diy unit, Palasr?
jea48
2,944 posts
 

Mdhoover, found these on diyaudio Forums

http://www.diyaudio.com/forums/attachment.php?s=&postid=328821&stamp=1077146064

http://www.diyaudio.com/forums/attachment.php?s=&postid=16083&stamp=1012084233

http://www.diyaudio.com/forums/showthread.php?s=&threadid=2080&highlight=

I use an EI isolation transformer ahead of my Arcam Alpha 9 CDP to eliminate dcv offset on its toroidal transformer. Have not tried the above filters.
jj2468
280 posts
 
Hi,
Maybe you guys can help me or point me in some direction.

My apartment seems to be the King of Hum.

About a year-and-a-half ago, I "upgraded" from a CJ amp to Art Audio monoblocs. To my dismay, they hum like a bumble bee. I've tried an Exact Power unit, a BP 3.5 and a humbuster. Not only did they not work, but each transformer within these devices hummed. About six months ago, I bought a turntable - and the speed controller hums. The vendor says he has hever heard of one of his speed controllers humming and suggested I have my wall socket tested. More on that in a moment.

The only device I found that kills 90% of the hum at the monoblocs is a PS Audio 1000; which I just sent to PS Audio because it is blowing my equipment fuses. (I should know shortly whether there is a defect with the PS Audio unit - and to PS Audio's credit they are examining it at no charge even though I bought it here on Agon). The PS Audio only kills the hum when I set it to mode #3, which according to PS Audio, "adds a little 3rd order harmonic distortion, which makes the transformers operate a little more efficiently". The PS Audio hums, but it is much quieter than the monoblocs. The PS Audio has no affect on the speed controller hum.

I have tried all sorts of versions of lifting the grounds. I have tested the grounds at the so wall socket, which are ok. I have unplugged what devices I can from my apartment one by one.

Any suggestions? If I hire an electrician to test the wall sockets, can anybody tell me exactly what I should ask him or her to test for? What do I do with the results once I know? I am adrift in hummmmmmmmmmmmmmmmmmmmmmm.

BTW, kudos to Conrad-Johnson for manufacturing the only amp that does not hum at Jeff's pad.

Jeff
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