EMI-filter power strips anywhere?

Have you tried Kilz? Or Greek-style... Windex ?:-) ...Jim Thompson

Windex, yes, how could I forget? According to Gus Portokalos it works :-)

I have a bunch of Tripp-Lite Isobars, and have been very happy with them. They have 3 filters in cascade, with a duplex outlet at each stage, so you get mutual filtering as well as incoming.

Cheers

Phil Hobbs

"Joerg"

And the mixer's circuitry is de-modulating the signals to audio - right ?

You will never fix the problem with a filter in the AC supply.

Only the biggest fools think that.

.... Phil

No, this is more like some big motor, maybe an air gate handler in the AC system or whatever. Can't hunt it because it doesn't last more than a few secs.

Gets in after the mixer channels are combined but before the common potmeters. We can turn all the input channels off and it's still there. If you turn down both masters it's gone. This is a big old Yamaha mixer.

Done it before. Except there I was allowed to pipe in a big Corcom filter. Fixed it, the noise never showed up again.

One has got to try. Of course, chances are it might be some electrolytic going bad on us or whatever.

FFS spell it out man.

No RF filter is gonna help ya if it is not.

There are a host of ways that RF and audio band noise can enter a mixing console, arriving via the AC lead is the LEAST likely of all.

It comes entirely naturally.

... Phil

Joerg, I would second on the tripplites, mine all seem to work.

Wouldn't be a place where a small UPS would help. would it? Although, those might add more noise than they removed...

Charlie

"Charlie E. Neuman"

And don't worry about any facts.

... Phil

How about a 120/120 V isolation transformer with preferably a static shield between primary and secondary ? With power levels typical in mixers, the transformer should not cost too much.

If unbalanced signal paths are used with the mixer, there is always the risk that some of the cable shields are carrying various noise currents and any resistance in the cable shield itself and the unbalanced connectors will cause a voltage drop that is directly added to the audio signal.

The f****it OP has no idea what the source of the noise is and so far has REFUSED to even describe what it sounds like. it.

Cos he is one vile, lying POS.

.... Phil

It is too long and regular for that. But not long enough to run and chase it. Unfortunately we do not have a recording. More like a brushed motor.

Line filters can. BTDT.

It can also come in through the speaker wires. If the line filter doesn't fix it that's the next job. Radiated interference is unlikely, although cannot be 100% excluded.

Nope. In that case it was easily proven. Flick big light switch, no more popping noise, everyone happy.

A UPS would be ok but seems overkill and we'd then have to worry about batteries wearing out. We'll buy the line filter that Phil Hobbs pointed out.

Might help but chances are low because such big mixers from reputable brands already have that.

Yes. But one of my past jobs on this audio booth was to make everything symmetrical that could be, and that has reduced hum and rat-tat-tat from large fluorescent banks but a lot. Literally eliminated it. This time we can slide all the potmeters to zero and that has no effect. Must come in somewhere else so the power line is one of the suspects.

We have a variable-speed ventilator motor on the roof. The controller belongs to Production but they installed it in our lab. It made 40 volt p-p spikes, nasty ringy things at mucho KHz, everywhere on our floor. We installed an expensive Grainger EMI filter with basically no effect, so we had to make our own, with some permalloy powder cores and some big film caps.

ftp://jjlarkin.lmi.net/Filter.JPG

I'd suggest you consider killing the noise at the source. Once it gets loose, it gets harder to keep it out of things.

Oh, the Irish guy who bent our conduit was an artist and a genius. I hacked the blue flexy thing... that's not his fault.

The roof is fun, except that it's raining now.

John

Yikes! Don't let the fire marshall see that. A tripping breaker will probably make a nice fat arc with all this inductance..

But yeah, I had to do the same in the lab. Had a Dell printer/scanner that had the sh...iest power supply I've ever encountered. Only a hand-rolled filter was able to get that muffled. But my inductors were in a box and I didn't use wire nuts (I hate those things).

The noise episodes are too short to hunt. Plus it happens during worship service and you can't go "s'cuze me" and plop a cherry picker in front of the pulpit to get into the ceiling 30ft above. Plus it would need a jet engine to get me up there in two seconds before the noise stops for the day :-)

Ok, the jet engine mod could obviously be arranged by Ron Patrick:

Did he sing Finnegans Wake while on the ladder?

Yeah, it's supposed to reach us in the afternoon.

The vile twit is you, Allison! You don't know electrical noise from the noise coming out your mouth.