Bad Ground, what can I do?

[Frost]

My girlfriend has a nice stereo, probably why she is my girlfriend . However she recently moved apartments. Now, the transformer in her amp buzzes most of the time. When I take the amp to another apartment, it does not buzz. It buzzes on all her outlets even with no load.

I have tested the wall outlets which sometimes show a ground and sometimes do not. Basically I think the ground is compromised. Although this is not a good electrical situation, I am aware that her landlord isnt going to fix it.

What can we do? Good Sized UPS? Use the cable companies ground? Good power conditioner?

Ideas?

Frost

[JTR]

if the wiring is faulty, it's a safety issue; never mind the stereo.
i'd put in a call to either the building inspections or fire depts.

[Geoff_T]

Originally posted by Frost
My girlfriend has a nice stereo, probably why she is my girlfriend . However she recently moved apartments. Now, the transformer in her amp buzzes most of the time. When I take the amp to another apartment, it does not buzz. It buzzes on all her outlets even with no load.

I have tested the wall outlets which sometimes show a ground and sometimes do not. Basically I think the ground is compromised. Although this is not a good electrical situation, I am aware that her landlord isnt going to fix it.

What can we do? Good Sized UPS? Use the cable companies ground? Good power conditioner?

Ideas?

Frost

Hi

Are you sure it's the transformer buzzing and not a buzz in the speakers?

It sounds fishy to me ground or no ground that the transformer buzzes as ground should not form part of the circuit path.

I agree with the other poster though... all your sockets must have a ground on them for safety's sake.

[Blackwater]

Anyone else here live in a 200 year old house?

[tINY]

I'm guessing that it's EMI you are hearing from a bad florescent or HPS light driver. It could be coupling through the power leads or through the air.




-tINY

[Geoff_T]

Originally posted by tINY


I'm guessing that it's EMI you are hearing from a bad florescent or HPS light driver. It could be coupling through the power leads or through the air.

-tINY

Hi

I agree.

The only reasons transformers normally buzz is that they are being overloaded or have a loose lamination stack. I'm suspicious that it is transformer noise and is actually, as you suggest, externally radiated interference heard through the speakers.

[Frost]

I am certian that this is the transformer buzzing. I took apart the amp because I assumed that it had come loose. I tightened the nut holding the donut in place and it helped but this IS a mechanical noise from the tranny. It makes this noise with no speakers attached. It only makes this noise when plugged in at her apartment. Im kinda baffled too.

Frost

[Geoff_T]

Originally posted by Frost
I am certian that this is the transformer buzzing. I took apart the amp because I assumed that it had come loose. I tightened the nut holding the donut in place and it helped but this IS a mechanical noise from the tranny. It makes this noise with no speakers attached. It only makes this noise when plugged in at her apartment. Im kinda baffled too.

Frost

Hi

Not a good idea to overtighten it as you could crush the windings...

There's no way that it's creating a shorted turn? Like if the bolt in the middle can touch the chassis at both ends?

Is the transformer hot when it buzzes?

Was the amplifier moved from another location? It may have moved something...

eg

The toroid has a low external field but radiation does escape out of where the wires exit. You may find that the toroid's stray field is being picked up by some sensitive piece of circuitry or even pc track if it forms a circle (as in copper flood around an area).

You may find that rotating the toroid minimises the pick up.

The toroid ought to sit on a soft rubber washer to protect the windings and must not be overtightened.

[tINY]

I have heard transformers buzz audibly, usually where there is a phase-controlled light dimmer drawing a lot of power.

If you have a scope with proper 300v probes, you may want to look at the waveform of the AC power....



-tINY

[Geoff_T]

Originally posted by tINY


I have heard transformers buzz audibly, usually where there is a phase-controlled light dimmer drawing a lot of power.

If you have a scope with proper 300v probes, you may want to look at the waveform of the AC power....

-tINY

Hi

I've used a 'scope connected to a small reel of equipment wire and used it as a search coil... especially near cable runs where the modulated/distorted waveform shows up nicely.

[Geoff_T]

Hi

This was on the Mix output noise of an SSL

You can see the low frequency switching pulses are enormous compared to the noise floor of the SSL.

The studio used electronic light dimmers for every light!

[tINY]

I bet there was an enormous hum at 100/120 Hz....



-tINY

[Geoff_T]

Originally posted by tINY


I bet there was an enormous hum at 100/120 Hz....

-tINY

Hi

You bet! You didn't need to put your ears next to the monitors!

It was a brand new studio with a 9000J.

They asked me to prove it was the lamp dimmers.... I think the loss of interference when we threw the breaker was pretty convincing!

Moral :- NEVER use solid-state lamp dimmers in a studio environment!

[Snatchman]

Originally posted by Geoff_T
Hi

This was on the Mix output noise of an SSL

You can see the low frequency switching pulses are enormous compared to the noise floor of the SSL.

The studio used electronic light dimmers for every light!

"IT'S ALIVE".....!

[Frost]

I brought the amp to my studio and to my house and it doesnt buzz in either location. Back at the girlfriends house it buzzes. So the problem is consistent with the apartment (tried kitchen, bedroom, and listening room). The amp is not broken.

Any other ideas before I start spending money?

My girlfriend has no idea how lucky she is to have people like the lead engineers from Neve trying to solve her audio problems . thanks geoff; and everyone who has given this 2 seconds of their time or more.

Frost

[Geoff_T]

Originally posted by Frost
I brought the amp to my studio and to my house and it doesnt buzz in either location. Back at the girlfriends house it buzzes. So the problem is consistent with the apartment (tried kitchen, bedroom, and listening room). The amp is not broken.

Any other ideas before I start spending money?

My girlfriend has no idea how lucky she is to have people like the lead engineers from Neve trying to solve her audio problems . thanks geoff; and everyone who has given this 2 seconds of their time or more.

Frost

Hi

Sooooo... does she have lamp dimmers in her apartment?

Can you run it on a 3 core extension lead from an outlet that does have a ground?

[Geoff_T]

Originally posted by djui5
Geoff,
If you don't mind....what studio was this?

Hi

I'd rather not... they are in litigation with the studio designer, I believe, and I don't want to draw attention to their dilemma.

This was about a year ago and I have to admit amazement that they didn't realise they'd have this problem.

[JTR]

Originally posted by Geoff_T
Hi

I'd rather not... they are in litigation with the studio designer, I believe, and I don't want to draw attention to their dilemma.

This was about a year ago and I have to admit amazement that they didn't realise they'd have this problem.

What kind of "studio designer" specs scr dimmers?

What kind of studio owner can afford the dosh for an SSL, yet isn't aware of a basic rule like this?

You can buy a Ferrari, but that don't guarantee you know how to drive it, I guess.

[David Kulka]

Ah yes, solid state dimmers. They were the bane of home studios and low budget outfits for many many years.

While I would never recommend them to anyone building a studio and still cringe when I see them, I'd also have to say that these critters are more common than ever these days, and rarely seem to pose much of a problem.

In general, modern analog gear is much more resistant to RF and line noise than the older gear, digital of course is immune. And the SCR dimmers themselves have improved; they radiate far less noise than the earlier models.

So -- while it pains me to say it -- I think that you can often get away with using them these days, especially in post and mix rooms. One thing's for sure, those "quiet" variac dimmers, which can easily cost $500 + to install, have largely gone the way of the dinosaur.

[JTR]

Originally posted by David Kulka
Ah yes, solid state dimmers. They were the bane of home studios and low budget outfits for many many years.

While I would never recommend them to anyone building a studio and still cringe when I see them, I'd also have to say that these critters are more common than ever these days, and rarely seem to pose much of a problem.

In general, modern analog gear is much more resistant to RF and line noise than the older gear, digital of course is immune. And the SCR dimmers themselves have improved; they radiate far less noise than the earlier models.

So -- while it pains me to say it -- I think that you can often get away with using them these days, especially in post and mix rooms. One thing's for sure, those "quiet" variac dimmers, which can easily cost $500 + to install, have largely gone the way of the dinosaur.

David -

I take it to mean by your description of "quiet" variac dimmers is that many are not actually so?
any brands to avoid or brands to get?
out of curiousity, is there an acceptable substitute for the variac type?

[Geoff_T]

Originally posted by David Kulka
Ah yes, solid state dimmers. They were the bane of home studios and low budget outfits for many many years.

While I would never recommend them to anyone building a studio and still cringe when I see them, I'd also have to say that these critters are more common than ever these days, and rarely seem to pose much of a problem.

In general, modern analog gear is much more resistant to RF and line noise than the older gear, digital of course is immune. And the SCR dimmers themselves have improved; they radiate far less noise than the earlier models.

So -- while it pains me to say it -- I think that you can often get away with using them these days, especially in post and mix rooms. One thing's for sure, those "quiet" variac dimmers, which can easily cost $500 + to install, have largely gone the way of the dinosaur.

Hi

I think that the problem in the studio I used as an example was that the whole darn building was wired up with remote control lamp dimming. The light swiches in every room send control signals to a huge equipment rack loaded with dimming modules. Then the lights were fed from the switched outputs of the rack.

That meant that it was possible for "chopped" ac to be present on bunches of wires throughout the building. It also meant that finding another way of doing it was pretty tricky!

I'd welcome a list of lamp dimming devices, zero-crossing or otherwise, that have minimal EMF radiation issues.

[Blackwater]

I must come to the defense of the variac. Probably because I use them and Mine are quiet and didn't cost me but $100 a piece.
They get noisy when they are broken and most people don't realize this when it happens.

You can pick up a 10-15 amp used one at ham radio swap meets for 20-30 bucks and if you go through David Riddle Co. he will sell you one for whatever use for around a hundred and custom make the housing.

If I didn't own these I probably wouldn't have replyed so take it for what it's worth.

[Geoff_T]

Originally posted by Blackwater
I must come to the defense of the variac. Probably because I use them and Mine are quiet and didn't cost me but $100 a piece.
They get noisy when they are broken and most people don't realize this when it happens.

You can pick up a 10-15 amp used one at ham radio swap meets for 20-30 bucks and if you go through David Riddle Co. he will sell you one for whatever use for around a hundred and custom make the housing.

If I didn't own these I probably wouldn't have replyed so take it for what it's worth.

Hi

I agree, you can find them in electronic junk stores if you shop around!


Or EBay, of course!

http://search.ebay.com/variac_W0QQfromZR40QQsojsZ1

http://cgi.ebay.com/ws/eBayISAPI.dll...739896032&rd=1

[David Kulka]

Guys, I did not mean to disparage the trusty variac and Chris, you don't need to defend them on my account. A variac is still the best way of dimming lights in a studio; if the budget allows or surplus units can be found, go for it.

My point was just that things have changed on both the send and receive end, and in my opinion the need for variac style dimmers isn't nearly as pressing as it used to be.

And JTR, I just meant that compared to solid state types, variac dimmers are "the quiet kind". There are only 2 or 3 brands out there, and all work well.

Having said that, I do recall a few studios that got themselves in trouble with variac dimmers. One little downside is that since they are essentially autotransformers, they do generate 60 Hz. hum fields which radiate for 2 or 3 feet. You don't want to park a tape machine beneath one, or have the summing circuitry of your console right next to one. Some floor plans failed to take this into account. But these days, many studios contain neither -- Protools, Procontrol -- so again, especially in project studios, much of this is now a non-issue.

[JTR]

As I'm reading all these very interesting replies, I'm remembering a studio I'm associated with that did an expansion earlier this year, prior to my going there to work on a project

I was having a very $$$ compressor I'd just purchased shipped direct to the studio from the dealer for use on the project...

Then the studio owner told me of the troubles they were having with the equip in the new control room: weird behavior, etc. etc.

After some investigation, turned out their electrician had wired the room's A.C. outlets for the gear INTO THE LIGHT DIMMERS

I got off the phone and had the shipment re-directed to my home base; I could only imagine what other wiring "surprises" were waiting for my new comp to be plugged into

[Rod Gervais]

Seems we've gotten off the point of helping this young fella here.

Frost,

I don't suppose that you have had the chance to check this in an adjacent apartment and see if the problem was local to your GF's unit or was a global issue?

It could be a multitude of problems here - and could take a lot of money to fix.

It would probably be easier for you to get a power-line filter for the amp. This is (of course) making the assumption (on my part) that the problem is conducted RFI vrs radiated RFI.

The filters can be extreemly effective and run less than 50 for decent quality filters.

However - if the problem is radiated RFI - you should just get ready to move - you aren't going to want to foot the bill for just tracing out the problem.

It took us 4 months once to figure out the source of a ground loop problem (at a studio) with a couple of good techs......... the fix took 15 minutes....... and maybe cost $30.00.

But tech time doesn't come cheap.


Now - as far as dimmer systems go - I have to agree with the sentiment that Variacs are the way to go (all other things being equal)

BUT - i have had some excellent results (for clients who desired this) with the Lutron GRAFIK Systems Preset Lighting Controls.

I've always been careful to make certain I never crossed the legs of gear and lighting - and also always used remote Lamp Debuzzing Coils.

The clients love the ability to have multiple lighting scenes available at a touch of a finger. That and no problems associated with RFI.

Best of all possible worlds.

Sincerely,

Rod

[Tim Farrant]

If you run a toroidal power transformer on a modified sine wave DC to AC convertor, then it will generally make an audible buzzing sound. This is because the output of the convertor is more or less a square wave (and not a sinewave), a similar effect to what you have here.

In your case Frost, it would appear to me that mains supply is similarly "dirty". This could be caused by a loose connection somewhere between the sub board and your girl friend's apartment. I would imagine that each apartment would have it's own master circuit breaker somewhere, and this could be faulty with the contact arcing over causing the dirty mains. This would explain why it does not buzz in other apartments. Try turning the master breaker on/off a few times to try and clean the contacts.

This is about all I can think of, hope it's of some help.

Tim.