Tranformer buzzes, toft, perreaux, mains

[matt thomas]

Hi

I have a number of buzzes around my studio.

The torroidal transformer in my Toft ATB 32 PSU buzzes
My perreaux power amp buzzes (the actual amp buzzes, but it seems to come through the speakers too, with nothing plugged into it) ( I assume its the transformer)
the only other place I can hear it is my mains meter box, which seems to buzz the same.

you can hear them all when standing in the same room as the device with no other sound happening.

Doing a search here on geek slutz seems to say the transformers are not sufficient quality. I don't think this is the problem as the equipment is quality stuff, especially the perreaux (current production model).

On google the common reply is that there is DC in the mains. Do you think this could be the case?

What can be done about it? An isolating transformer?

thanks in advance
narco

[rotation]

Problematic ground?

[matt thomas]

I don't think so, and as far as I know that wouldn't cause this problem? that would cause hums in the audio signal, not buzzes from the transformers? (correct me if I'm wrong)

narco

[rotation]

It's strange that so many things buzzes. Yeah, you are right that if it would be grounding e would hear it in audio signal.
So what it can be than? Underrated transformers?

[Dan Kennedy]

There is a lot more distortion on the mains power now than there used to be, mostly because of the large number of high powered switching supplies used. Power factor correction helps this, but it isn't implemented everywhere.

This is what causes the "DC" on the waveforms, it's basically residually DC because the waveform becomes asymmetrical. It's the harmonics of the 50-60hz you hear.

An isolation transformer may help, as it will filter some of the harmonics out.

There might also be a problem with a 60hz designed transformer getting used on your local 50hz. But most manufacturers will have a properly sized transformer with plenty of slop factor.

[David Kulka]

Yes, it's unusual to have acoustic buzzing on several transformers at the same time.

We have serviced many Perreaux amps and I have never heard transformer noise on any of them. They used very good quality transformers.

I agree with the comment above...DC on the line is unlikely and the term is a little misleading...but certain kinds of loads can cause asymmetrical waveforms, which can amount to the same thing. A tech can check this with a scope. Since high voltage is involved and the scope is unbalanced, this must be done carefully. A small step down transformer can be used, which makes the operation much safer.

If you do find that the AC sine wave has significant distortion, there's a good chance your power company would take care of this.

[matt thomas]

I should add I'm in a very industrial area, right next door is a metal worker, arc welders and all

I don't have easy access to a scope, but I can get an isolation transformer to try, so I'll try that first

thanks for your thoughts so far

narco

ps. I can hear what seems to be the same buzz in the phone line too, which isn't attached to the mains, perhaps its radio interference, but I wouldn't think this woud make transformers buzz. I think the phone line might be something different

[Tim Farrant]

Try taking the amp to a friends house, see if it buzzes there, that would eliminate the equipment transformers as the cause. You might need to get a power conditioner, a passive one.

[matt thomas]

Originally Posted by Tim Farrant

Try taking the amp to a friends house, see if it buzzes there, that would eliminate the equipment transformers as the cause. You might need to get a power conditioner, a passive one.

whats a "passive" power conditioner?
(there is so much misinformation on the subject of power conditioning, what would ou recommend?)

narco

[Tim Farrant]

I have installed these before in studios, they had a big auto transformer and capacitors in them - very heavy and large. A quick search did not reveal anything similar, but I did find this which might help you..

Line-R 1200VA Automatic Voltage Regulator

[matt thomas]

thanks tim

I know of a place in auckland here that sells these kinds of things, although they know nothing about audio when asked.

if you click on this page

MasTec International Product Clearance

and search for "soltec AHA"

would these kind of things be suitable? theyre online
UPS's

thanks for your help
narco

[matt thomas]

ok, update

I bought a power conditioner that I found on the local auction website for $5. It is a Sola 200. I couldn't find much info (that I understood) for it online, but I did find an audio hirage place in Austrlia that hired it out for $130 a week, so I figured it was a good deal and couldn't hurt to try.

So I plugged it in, and guess what ?

yes, the power conditioner hums (great), and yes, I mean the actual unit.

Interestingly it didn't hum when I first plugged it in, but it did 8 hours later, when I plugged it in for the second time.

Plugging my perreaux into it made the buzz from the amp more muffled sounding, which was an improvement, but still far from ideal.

The buzzes don't end up on my recordings, but they are irratating to put up with

narco

[Tim Farrant]

Oh shit, it's going from bad to worse!

You might need to get a electronic conditioner as opposed to a passive one. It's obvious the mains incoming to your place is not clean. You might want to contact your power supplier, because in NZ we do have quite stringent rules on the quality of the mains provided to consumers, and if it's not up to spec because of your noisy neighbours, they need to do something about.

[matt thomas]

hey tim

I should have guesed you'd be the expert on buzzes , expecially in New Zealand,

Anyway, I have mercury energy technician coming around withint the next hour to check the power

(edit: they've been and gone, they're sending someone else around tomorrow with a bit more expertise and an oscilloscope )

narco