[johnsonad]

I just moved apartments and maybe it is that this place is more quite but I notice that my CDP, power amp and sub amps in my speakers are buzzing/humming. There is also an audible hum from the speakers. Is this normal and something I've missed before or could the power be causing this? Thanks!

 

[pmillett]

It may be your power. It's possible that the line voltage is higher, and/or there's some DC component to it. In either case, you can wind up getting saturation in the power transformers, which causes them to buzz...

Pete

 

[Bjornboy81]

I highly doubt DC on the utility line, but I agree with a higher line voltage. The transformers in these components should be able to take 125VAC or so, but they are probably still nearing the saturation curve of the core.

 

[johnsonad]

Is this something I can check with my multimeter that is, measure the voltage at the outlet?

 

[Bjornboy81]

Yeah, just put the two leads in the two slots on the recepticle and check the AC voltage.

 

[sejarzo]

I foresee this becoming a bigger and bigger problem.

My Hsu Research powered sub was emitting a slight hum even when it was only on standby.....and when I put my head down next to the floor, I realized it was not coming from the woofer, but the plate amp itself on the back.

Eventually Hsu tech support and I got it down to possibly high supply voltage, and I measured it to be 124.7 to 125.3 VAC (on a cheap meter, but it compared perfectly to the calibrated Flukes that our instrument techs had at the plant.) The voltage selector on the Hsu amp PSU is for 115/230 VAC. Also, I found no significant or constant DC voltage present, just a few tenths of a volt if anything.

At the urging of the tech at Hsu, I called our utility, and they sent someone out who confirmed that reading--who told me that the "new spec" is 120 VAC +/- 5%....so that means they can run up to 126 VAC and still be fine in their eyes. An old friend is an EE for a utility, and I mentioned my dilemma to him one day. He said "off the record" that there's one way to increase power output over existing copper lines that are reaching their current-carrying limit, and that's to pump up the voltage! A lot of homes have been built in our area, with no new substation to be seen--kinda makes sense, eh???

I'm 50, and when I was growing up in the early 1960's everyone referred to the voltage in homes as "110 volts", never 115 or 120...which I think is some evidence of the trend.

Around that same time, I had a Cambridge Audio 640Cv1 CD player, and it was similarly affected--you could actually feel the entire unit vibrating rather than simply hearing the hum. The North American importer for Cambridge Audio pulled a few from his stock, and he found the same thing.

I considered buying an inexpensive variac to see if reducing voltage to the 115 VAC range had any impact, but decided even an inexpensive one was too much to spend just to verify that--and I don't know of anyone around with one to borrow.

Presuming that my gear was not otherwise defective, unless manufacturers come to grips with the fact that a lot of US consumers are now supplied at 125VAC or so, it could present a problem for many more users.

 

[Nebby]

My power here in Japan is supposed to be 100, but generally runs at 103-105v. My Japanese Denon receiver has no issues with the extra 3-5v of power, as it acts normally.

A year or so ago I picked up a Monster Cable variac for my american audio stuff, and I tried hooking up my to see what effect running the receiver at 120v instead of 100v would have, and I got the same humming/buzzing you describe. I also measured the temperature of the vents on the top of the receiver and it was running a few degrees C hotter. So overvolting may be the issue you're having. What voltage is labeled on your equipment? 115? 110v? if it is rated for 120v, then something else is the issue; perhaps some DC ripple is on the line like nikongod states a few posts down.

 

[webbie64]

Quote:

Originally Posted by Nebby /img/forum/go_quote.gif I tried hooking up my Japanese Denon receiver to see what effect running it at 120v instead of 100v, and I got the same humming/buzzing you describe. I also measured the temperature of the vents on the top of the receiver and it was running a few degrees C hotter.

Same issues of hum and heat here running US equipment from a transformer box that puts out, you guessed it, 120v

 

[johnsonad]

Damm, just got the results. Most outlets are 120.6. The outlet I found to be the quitest by trying all in the living room is 119.6. This outlet after my SACDmods conditioner is 118.2. There is no way that San Diego power is going to do anything about it so I'll have to take care of it another way. Any recommendations? I'm a big fan of great technology at an even better price

 

[nikongod]

check for a DC rider on the mains. although rare it can reap havoc on a transformer. toroidal transformers are FAR more succeptable to this rubbish than EI and other transformers, but it can happen to anything.

if you have some DC, an isolation transformer can do wonders for you. I would not bother with "foofy audiophile" types, any medical or scientific instrument grade (for life support machines, and electron microscopes, amongst other things which are trivial by audio standards

) isolation transformer should work. bonus round, they can sometimes be found surplus, all cased up and ready to plug in.

You can also find 125->115V isolation transformers, which would solve BOTH the high voltage issue AND a DC rider.

 

[Nebby]

Quote:

Originally Posted by webbie64 /img/forum/go_quote.gif Same issues of hum and heat here running US equipment from a transformer box that puts out, you guessed it, 120v

That's odd, are the devices that are hooked up to it rated for 120? They should have a label next to the IEC inlet that says what they're rated/designed for.

 

[webbie64]

Quote:

Originally Posted by Nebby /img/forum/go_quote.gif That's odd, are the devices that are hooked up to it rated for 120? They should have a label next to the IEC inlet that says what they're rated/designed for.

McAlister EA-4 (low hum) and Apuresound DAC (greater hum with increasing heat). Both perform quite well, just have the hum issue. Smaller portable DAP rechargers fitted to the transformer box have no issues.

 

[johnsonad]

I measured for DC as best as I know how and it ranged from 50mV to 62mV per socket. I also went back to the old place and measured. In the two sockets I used before it was only 20mV. I don't know if that little DC would make any difference at all.

My CDP is rated for 115v and everything else is 120v. I can understand the CDP but I don't understand why the power and sub amps would hum with 120.6v. Really though I'm blowing this all out of proportion. The music sounds great and it's only during very quite passages that I can hear a slight hum from the power amp. Otherwise the hums are only audible when I get close to them. It's probably in the best interest of my pocket book to leave it alone....

With the CDP, can you change out the transformer to one that is rated for 120v instead of the 115v? That would seem to be the cheapest and easiest thing to do.

 

[Bizzel]

Quote:

Originally Posted by sejarzo /img/forum/go_quote.gif I'm 50, and when I was growing up in the early 1960's everyone referred to the voltage in homes as "110 volts", never 115 or 120...which I think is some evidence of the trend.

It's the loudness war all over again! Don't let the cable forum get wind of this...

 

[sejarzo]

I recall now that one of the other reasons I didn't go for a $39 variac is that as a rule, inexpensive variacs usually hum so it would likely have been an academic exercise only.

There was a thread about this issue on an audio forum sometime ago--the problem was that a fairly expensive isolation xfo that someone acquired "solved the problem" in that the audio gear no longer hummed, but the xfo itself would hum instead.

nikongod.......any comment on that?

There's a guy on Audiogon who used to sell surplus Powervar isolation/conditioning units for $150 or so plus shipping, but the only ones he's selling now are prettied-up models for $280 plus shipping (they're heavy, too....so shipping is a significant cost.)