Bad mains power - popping mixer

[Gordon Airporte]

I just got a new mixer to go with the new soundcard in my PC rig and
every time the window-unit air conditioner comes on I get a pop/crack in
my monitors. I'm monitoring with headphones plugged into the mixer.
(Previously I had my headphones plugged directly into a consumer
soundcard, and I didn't have this problem.)
The mixer is on a generic power strip/surge suppressor with the
computer, and the AC is on a separate breaker. That's what's confusing
me. What can be done?

[Mark]

Gordon Airporte wrote:
> I just got a new mixer to go with the new soundcard in my PC rig and
> every time the window-unit air conditioner comes on I get a pop/crack in
> my monitors. I'm monitoring with headphones plugged into the mixer.
> (Previously I had my headphones plugged directly into a consumer
> soundcard, and I didn't have this problem.)
> The mixer is on a generic power strip/surge suppressor with the
> computer, and the AC is on a separate breaker. That's what's confusing
> me. What can be done?

Do you hear the pop with the headphones connected to the mixer and
NOTHING else connected ot the mixer?

And with all the faders down?

Mark

[Gordon Airporte]

Mark wrote:

> Do you hear the pop with the headphones connected to the mixer and
> NOTHING else connected ot the mixer?
>
> And with all the faders down?

Well, it doesn't want to be repeatable; I can't get it to pop when I
want it to, but it still does when I'm not expecting it. I did notice
that it pops when the AC turns /off/, not on. I hadn't noticed before
because if I had my headphones on I was listening to music, making the
AC's air flow hard to hear. I'm sitting here now with only the cans
plugged into the mixer, hoping something will happen, though.
What are my options either way - if it does and does not pop with no
inputs plugged in/turned up? Would something like a power conditioner help?

[Anahata]

Gordon Airporte wrote:

>
> Well, it doesn't want to be repeatable; I can't get it to pop when I
> want it to, but it still does when I'm not expecting it. I did notice
> that it pops when the AC turns /off/, not on.
[...]
> What are my options either way - if it does and does not pop with no
> inputs plugged in/turned up? Would something like a power conditioner help?

Try fitting some suppression components around the AC switch, if you
have access to its power wiring.

It's barely relevant whther your faders are up or down or inputs plugged
in etc. - if your suppress it at source it shuldn't get in anywhere.

Suppression possibilities:
- encasing the AC power feed in metal conduit or using screened power
cable (in casr the interference is being radiated)
- capacitor across the incoming supply to the AC unit
- capacitor or series RC network across the motor, downstream of the switch
- capacitor or RC network across the switch contacts

Also note that your surge supressor in the power strip is just that - it
doesn't filter out RF interference. Some suppression components there
wouldn't do any harm. Yes, a power conditioner might help.

Anahata

[Laurence Payne]

On Tue, 22 Aug 2006 01:31:00 -0400, Gordon Airporte >
wrote:

>
>Well, it doesn't want to be repeatable; I can't get it to pop when I
>want it to, but it still does when I'm not expecting it. I did notice
>that it pops when the AC turns /off/, not on. I hadn't noticed before
>because if I had my headphones on I was listening to music, making the
>AC's air flow hard to hear. I'm sitting here now with only the cans
>plugged into the mixer, hoping something will happen, though.
>What are my options either way - if it does and does not pop with no
>inputs plugged in/turned up? Would something like a power conditioner help?

Does the click get onto the recording? If not, live with it. If it
does, turn the AC off when recording.

[Ethan Winer]

Gordon,

> every time the window-unit air conditioner comes on I get a pop/crack in
my monitors. <

See this article from Recording magazine. It's exactly what you need:

www.ethanwiner.com/dimmers.html

--Ethan

[Gordon Airporte]

Anahata wrote:

> Try fitting some suppression components around the AC switch, if you
> have access to its power wiring.

Thanks for the comprehensive response. Yeah, I've taken it all apart to
clean it before, so I can get in there. Unfortunately, I've never
learned all I'd like to know about electronics. Can you give me a
specific capacitor spec to put across the AC's power leads? Messing with
wall power isn't something I want to get wrong.
In the mean time I'll look into some kind of shielding. I didn't know it
was RF I was dealing with - so it's in the air and not the lines?

[Eeyore]

Gordon Airporte wrote:

> I just got a new mixer to go with the new soundcard in my PC rig and
> every time the window-unit air conditioner comes on I get a pop/crack in
> my monitors. I'm monitoring with headphones plugged into the mixer.
> (Previously I had my headphones plugged directly into a consumer
> soundcard, and I didn't have this problem.)
> The mixer is on a generic power strip/surge suppressor with the
> computer, and the AC is on a separate breaker. That's what's confusing
> me. What can be done?

The surge suppressor is irrelevant.

What you're hearing is the combination of 2 cheap pieces of kit. One of them
creates interference and the other has no 'defences' against it.

Use a *filter*.

Graham

[Eeyore]

Gordon Airporte wrote:

> Can you give me a
> specific capacitor spec to put across the AC's power leads?

Will do bugger all. Don't even try it. You need inductance too, as in a filter.

Graham

[John Phillips]

"Gordon Airporte" > wrote in message
. ..
>I just got a new mixer to go with the new soundcard in my PC rig and every
>time the window-unit air conditioner comes on I get a pop/crack in my
>monitors. I'm monitoring with headphones plugged into the mixer.
>(Previously I had my headphones plugged directly into a consumer soundcard,
>and I didn't have this problem.)
> The mixer is on a generic power strip/surge suppressor with the computer,
> and the AC is on a separate breaker. That's what's confusing me. What can
> be done?

If the air conditioner is 120VAC, then I can suggest a couple easy things to
try.

1. Install a generic power strip (with surge protection) on the power plug
to the air conditioner in addition to the one on PC. This would be a "gift"
if it would work, at least it is cheap to try.
2. If number 1 above does not work, get one of the more sophisticated line
LC filters and install it on the air conditioner. If it helps then get one
and install it on your computer. If it does not fix that problem then it is
always a good idea to have power line filtering on your PC. Install it
before the UPS if you use one.

John Phillips

[Eeyore]

John Phillips wrote:

> 1. Install a generic power strip (with surge protection) on the power plug
> to the air conditioner in addition to the one on PC.

'Surge protectors' are totally irrelevant to this.

Graham

[Chris Hornbeck]

On Mon, 21 Aug 2006 16:30:42 -0400, Gordon Airporte >
wrote:

>I just got a new mixer to go with the new soundcard in my PC rig and
>every time the window-unit air conditioner comes on I get a pop/crack in
>my monitors. I'm monitoring with headphones plugged into the mixer.
>(Previously I had my headphones plugged directly into a consumer
>soundcard, and I didn't have this problem.)

You're hearing the problem upstream of your DAW; it's reasonably
safe to assume the issue is also upstream.


>The mixer is on a generic power strip/surge suppressor with the
>computer, and the AC is on a separate breaker. That's what's confusing
>me. What can be done?

Good. If your incandescent lights don't blink with the
AC cycling, it's probably not an issue of line voltage,
per se.

Leaving, as several have suggested, issues of RFI, fortunately
easier to solve than to discuss. Safely tackling the problem
at its source is way, way beyond a Usenet posting, but a
few ferrite cores around *each and all* wires going to and
coming from (including the power cord) your mixer is a
good cheap alternative.

Split clamp-on ferrites should be as close to the mixer as
practical. If there's extra room in the ferrite's gap, wrap
the wire around and through some more times.

Also helps for lightning protection. Strange, but true.

All good fortune,

Chris Hornbeck
"History consists of truths which in the end turn into lies,
while myth consists of lies which finally turn into truths."
- Jean Cocteau

[Steigs]

You may also want to try to borrow or rent a balanced balanced power
system, something like the EquiTech series, to see if it helps your
situation any.

No guarantee, but mine has cleaned up the power here tremendously.

-Steigs


Gordon Airporte wrote:
> Anahata wrote:
>
> > Try fitting some suppression components around the AC switch, if you
> > have access to its power wiring.
>
> Thanks for the comprehensive response. Yeah, I've taken it all apart to
> clean it before, so I can get in there. Unfortunately, I've never
> learned all I'd like to know about electronics. Can you give me a
> specific capacitor spec to put across the AC's power leads? Messing with
> wall power isn't something I want to get wrong.
> In the mean time I'll look into some kind of shielding. I didn't know it
> was RF I was dealing with - so it's in the air and not the lines?

[Scott Dorsey]

Steigs > wrote:
>You may also want to try to borrow or rent a balanced balanced power
>system, something like the EquiTech series, to see if it helps your
>situation any.
>
>No guarantee, but mine has cleaned up the power here tremendously.

In most cases, the balanced power boxes are effective because they act
as low-pass filters and as isolation transformers. For the most part,
the actual balancing isn't a big deal.

I do think, though, that it's foolish to spend huge amounts of money on
power filtration in order to use equipment with crappy power supply design.
The real solution is to have properly-designed power supplies with good
noise rejection in the first place.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Gordon Airporte]

Scott Dorsey wrote:
> I do think, though, that it's foolish to spend huge amounts of money on
> power filtration in order to use equipment with crappy power supply design.
> The real solution is to have properly-designed power supplies with good
> noise rejection in the first place.
> --scott

I only need a few channels and there seem to be only a couple of options
here - a Tapco and a Beheringer. I got the Tapco. Unfortunately it looks
like they decided to make the device even cheaper than it would be with
just 5 channels and cut some corners in the design. :-P

[Gordon Airporte]

Ethan Winer wrote:

> See this article from Recording magazine. It's exactly what you need:
>
> www.ethanwiner.com/dimmers.html
>
> --Ethan

Hey, so it is. Thanks.

[Gordon Airporte]

Chris Hornbeck wrote:

> Split clamp-on ferrites should be as close to the mixer as
> practical. If there's extra room in the ferrite's gap, wrap
> the wire around and through some more times.
>
> Also helps for lightning protection. Strange, but true.

Thanks, I'd forgotten about these. It's not terribly practical to clamp
every cable, but it's better than wrapping the mixer in tin foil ;-).

[John Phillips]

"Eeyore" > wrote in
message ...
>
>
> John Phillips wrote:
>
>> 1. Install a generic power strip (with surge protection) on the power
>> plug
>> to the air conditioner in addition to the one on PC.
>
> 'Surge protectors' are totally irrelevant to this.
>
> Graham
>

Depending on the nature of the pop, it can help. It is always best to stop
the pop at its source. If the pop represents a large electrical spike
caused by the AC, like my old refrigerator did, it can reduce the spike by
clipping some of it. The surge protectors will work in both directions, the
spike can originate from the power grid or the AC. In both cases, the surge
suppressor can absorb some of the energy.

[w_tom]

Noise - the pop - is a voltage of mabe ones or tens of volts. Surge
protector ignored all voltages less than hundreds of volts. The number
is even listed on its box: let-through voltage 330 volts. What is
that number on your surge protector? Somehow single digit voltages
that cause pops will be stopped by a power strip surge protectors? Of
course not.

If a refrigerator is creating voltages so high as to cause that pop -
330+ volts - then you are trooping to the hardware store daily to
replace dimmer switches, smoke detectors, clock radio, etc. The
refrigerator is even a threat to itself.

It is a classic example of why we first learn the numbers before
knowing anything. Even a number on that protector's own box says the
protector will ignore 'pops' from a refrigerator.

Meanwhile, another number no provided on that box says that if the
refrigerator is creating 330+ volt spikes, then the protector will
degrade quickly (in weeks or months) and must be replaced excessively.
Just another reason why the protector is not a solution to those pops.

Pops from appliances power cycling are supposed to be made irrelevant
by the audio electronics' own power supply. So if the power supply is
defective (insufficient), the missing filters should be installed on
its power cord. They are called 'AC line filters' to meet numerous
requirements including CE, CISPR22 & FCC part 15. Examples include
products manufactured by Corcom and Schuter to perform noise line
filtering and operate like this:
http://www.cor.com/PDF/Q.pdf

Yes it depends on the noise source. But household appliances such as
air conditioners that generate more than 330 volts must be removed from
the building as a threat to human life and to themselves. Pops from an
appliance power cycling is typically single digit volts.

John Phillips wrote:
> Depending on the nature of the pop, it can help. It is always best to stop
> the pop at its source. If the pop represents a large electrical spike
> caused by the AC, like my old refrigerator did, it can reduce the spike by
> clipping some of it. The surge protectors will work in both directions, the
> spike can originate from the power grid or the AC. In both cases, the surge
> suppressor can absorb some of the energy.

[John Phillips]

"w_tom" > wrote in message
ups.com...
....
> Meanwhile, another number no provided on that box says that if the
> refrigerator is creating 330+ volt spikes, then the protector will
> degrade quickly (in weeks or months) and must be replaced excessively.
> Just another reason why the protector is not a solution to those pops.

The frequency of replacement depends on the energy in the pops and the
capability of the MOVs.

.... So if the power supply is
> defective (insufficient), the missing filters should be installed on
> its power cord. They are called 'AC line filters' to meet numerous
> requirements including CE, CISPR22 & FCC part 15. Examples include
> products manufactured by Corcom and Schuter to perform noise line
> filtering and operate like this:
> http://www.cor.com/PDF/Q.pdf

I guess that you did not see my first post where I suggested this as a
second thing to try if the cheap surge strip did not help.

I agree that if the pop is that small, then the cheap surge protector will
not help. I did not know the magnitude of the pop in terms of volts so that
is good information for me also. I have a 30 year old refrigerator that did
the exact same thing that was described by the OP. I solved my problem by
putting one of the noise suppressor/filter boxes on the refrigerator, it
worked well. I do not recall the brand but it had MOVs and LC filters. In
my case, it was the LC filters that did the trick.

Thanks for the additional information.

John Phillips

[w_tom]

John Phillips wrote:
> I agree that if the pop is that small, then the cheap surge protector will
> not help. I did not know the magnitude of the pop in terms of volts so that
> is good information for me also. I have a 30 year old refrigerator that did
> the exact same thing that was described by the OP. I solved my problem by
> putting one of the noise suppressor/filter boxes on the refrigerator, it
> worked well. I do not recall the brand but it had MOVs and LC filters. In
> my case, it was the LC filters that did the trick.

One reason why MOVs cannot be used on telephone and cable TV coax is
its high capacitance. It is possible that MOVs in a cheap power strip
protector acted as capacitors to safety ground. This same function is
provided by .0001 uf (ballpark number) type capacitors on each AC power
wire to chassis ground in some appliances. Current through that
capacitor is small enough to not trip a GFCI and large enough to be
felt when appliance safety ground is not connected.

But again, an audio appliance should have sufficient power supply
filtering to make that popping irrelevant.

Those with even higher demands (recording studios) may also use
series mode filters (Zerosurge, Brickwall, Surgex, etc). Serious money
for a serious solution.

Generally appliance will put a snubber across switches to prolong
switch life and to further suppress that noise. Possible that a
snubber across that refrigerator power switch has failed.
Refrigerators are usually pretty good about providing a schematic (with
wire color codes) that would identify that snubber and switch. Some
additional solutions proposed.

[Scott Dorsey]

w_tom > wrote:
> One reason why MOVs cannot be used on telephone and cable TV coax is
>its high capacitance. It is possible that MOVs in a cheap power strip
>protector acted as capacitors to safety ground. This same function is
>provided by .0001 uf (ballpark number) type capacitors on each AC power
>wire to chassis ground in some appliances. Current through that
>capacitor is small enough to not trip a GFCI and large enough to be
>felt when appliance safety ground is not connected.

But, MOVs _are_ used on telephone and cable TV coax lines. They aren't
the same kind as you see on power lines, but they are zinc-oxide clamps.
These days you hardly ever see resistive fuse packs on phone lines any
more.

> But again, an audio appliance should have sufficient power supply
>filtering to make that popping irrelevant.

We're talking about MI store gear here. I agree that well-designed gear
will have good supply filtering, but so much of the MI-grade gear has very
marginal power supply design in the name of cost containment.

> Those with even higher demands (recording studios) may also use
>series mode filters (Zerosurge, Brickwall, Surgex, etc). Serious money
>for a serious solution.

For the most part, I have found these devices much less useful than the
manufacturers claim. The Surgex systems that I tried were actually less
effective than ordinary ferroresonant transformers at dealing with large
line peaks from arc welders and M-G sets. And they were more expensive
too.

> Generally appliance will put a snubber across switches to prolong
>switch life and to further suppress that noise. Possible that a
>snubber across that refrigerator power switch has failed.
>Refrigerators are usually pretty good about providing a schematic (with
>wire color codes) that would identify that snubber and switch. Some
>additional solutions proposed.

I very seldom see snubbers in appliances, but I agree that they'd sure
be a good idea. But then again, most of the appliances I have opened
up have been pre-1970 models.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[w_tom]

Scott Dorsey wrote:
> But, MOVs _are_ used on telephone and cable TV coax lines. They aren't
> the same kind as you see on power lines, but they are zinc-oxide clamps.
> These days you hardly ever see resistive fuse packs on phone lines any
> more.

Telephone lines even in the 1960s used 'the carbons' which were MOV
similar but used different construction to lower capacitance. Current
telephone technology (past 20 years) uses semiconductor based
protectors with lower capacitance.

Cable operating at even higher frequencies cannot use MOV. Often a
cable guy will first remove the plug-in protector from a cable
connection to restore signal strength.

MOVs are popular for AC electric because that capacitance is not
harmful and because MOVs can shunt so much power for so little cost.

[GregS]

In article . com>, "w_tom" > wrote:
>Scott Dorsey wrote:
>> But, MOVs _are_ used on telephone and cable TV coax lines. They aren't
>> the same kind as you see on power lines, but they are zinc-oxide clamps.
>> These days you hardly ever see resistive fuse packs on phone lines any
>> more.
>
> Telephone lines even in the 1960s used 'the carbons' which were MOV
>similar but used different construction to lower capacitance. Current
>telephone technology (past 20 years) uses semiconductor based
>protectors with lower capacitance.
>
> Cable operating at even higher frequencies cannot use MOV. Often a
>cable guy will first remove the plug-in protector from a cable
>connection to restore signal strength.
>
> MOVs are popular for AC electric because that capacitance is not
>harmful and because MOVs can shunt so much power for so little cost.

I put MOV's on the phone line before with no effects.
I did not have DSL.

greg

[[email protected]]

Gordon Airporte wrote:
> Anahata wrote:
>
> > Try fitting some suppression components around the AC switch, if you
> > have access to its power wiring.
>
> Thanks for the comprehensive response. Yeah, I've taken it all apart to
> clean it before, so I can get in there. Unfortunately, I've never
> learned all I'd like to know about electronics. Can you give me a
> specific capacitor spec to put across the AC's power leads? Messing with
> wall power isn't something I want to get wrong.
> In the mean time I'll look into some kind of shielding. I didn't know it
> was RF I was dealing with - so it's in the air and not the lines?

The best capacitor I have found is a polypropelene type 630VCMC .1 uF.
You can also buy it witht the 100 ohm resistor attached. Sometimes
adding caps can cause problems. This cap would go across the AC.
Putting caps from AC to ground is also necessary at times and may also
cause problems. Popping noises is most often ground loop related.
Filtering ground is not a often talked about subject. Filtering at the
source is the best method.

greg

[Scott Dorsey]

w_tom > wrote:
>Scott Dorsey wrote:
>> But, MOVs _are_ used on telephone and cable TV coax lines. They aren't
>> the same kind as you see on power lines, but they are zinc-oxide clamps.
>> These days you hardly ever see resistive fuse packs on phone lines any
>> more.
>
> Telephone lines even in the 1960s used 'the carbons' which were MOV
>similar but used different construction to lower capacitance. Current
>telephone technology (past 20 years) uses semiconductor based
>protectors with lower capacitance.

For the most part you'll see sidactors and the like installed by the
telcos. But there are still lots of MOV-based devices out there. Citel
makes some popular ones.

> Cable operating at even higher frequencies cannot use MOV. Often a
>cable guy will first remove the plug-in protector from a cable
>connection to restore signal strength.

The cable protector devices are transmission lines whose dielectric is
a zinc oxide powder. The capacitance of the MOV is made into part of
the line. They aren't just cheapie disc MOVs soldered across a coax or
anything, they are specifically designed for the job.

Lots of narrowband RF systems use bandpass filters for spike rejection...
most of the stuff in the spike isn't in the operating frequency of the
system so it gets rejected. This is very effective for stuff like land
mobile and FM broadcast but it's obviously impossible for a broadband system
like cable.

> MOVs are popular for AC electric because that capacitance is not
>harmful and because MOVs can shunt so much power for so little cost.

Right. The capacitance may even be an advantage.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."