Topic: PA Buzz-Is there a way to remove it?

[gratefulphish]

I know that the answer to this will probably be in computer recording, but it is a common enough issue that I thought that I would post the question here.  If there is a constant buzz coming through a PA, is there a way of isolating that frequency, and then reducing or eliminating it with a paragraphic equalizer?  I have not had time to really work with the shows involved.  I am sure that I could find a non-musical passage, and look at it with the spectrum analyzer in SF8, but I don't know how wide a frequency range such a buzzing sound might have, and whether the reduction of that frequency would otherwise have a serious detrimental impact on the music.  I was just wondering whether anyone had experimented with this or any other method to deal with this unfortunately not uncommon issue.  TIA

[bluegrass_brad]

If it is a ground loop hum then it is going to be at 60hz. Unless it was recorded in Europe and then it is going to be around 50hz

[Brian]

and if it's more than a hum then you have to think about possibly removing the nasty octaves of 60Hz.  this could degrade the overall quality of your recording though.

[Church-Audio]

I know that the answer to this will probably be in computer recording, but it is a common enough issue that I thought that I would post the question here.  If there is a constant buzz coming through a PA, is there a way of isolating that frequency, and then reducing or eliminating it with a paragraphic equalizer?  I have not had time to really work with the shows involved.  I am sure that I could find a non-musical passage, and look at it with the spectrum analyzer in SF8, but I don't know how wide a frequency range such a buzzing sound might have, and whether the reduction of that frequency would otherwise have a serious detrimental impact on the music.  I was just wondering whether anyone had experimented with this or any other method to deal with this unfortunately not uncommon issue.  TIA

The problem with buzz is there are harmonics and depending on how many harmonics. It can be very difficult to get rid of. If your just dealing with a few you can try and use a parametric eq try boosting the band first, with a narrow Q and sweep around until you find it. But less is more. Its very hard to say with out hearing it.

Chris

[rePat]

I remember reading a cool article in Relic Magazine, about making a reverse filter for this type of problem.  It used CEP/Audition.  Wish I would haved saved it!  It involved taking a very small section of silence, that isolates the buzz, and then making the filter for that frequency.  Sorry I don't have more specific details.

Pat

[gratefulphish]

The filter idea sounds like it might work.  I will have to experiment when I have a little time (LOL at self).

[anodyne33]

If it is a ground loop hum then it is going to be at 60hz. Unless it was recorded in Europe and then it is going to be around 50hz

Good call... never would have thought to add that!

fwiw

I had an issue last year with an acoustic show that I taped. It was a really quiet show and I ended up sitting in the back of the room right next to the power amps. (long story) The fans were really prevalent on my tape, so I used (don't cringe) the de-noise feature in Audacity, and with a little tweaking I was able to significantly reduce the white noise without adding a ton of artifacts from the "plug in". I can still hear the artifacts at times, but for me, it's less bothersome than listening to power amps.

If you're using SF8 I'm sure that you can find a de-noising plugin that should work well.

[Krispy D]

simple record archiving software has this type of feature.  you isolate the 'pops' and then filter them out.  Try experementing you'll find something that works.  just don't forget to save an unedited copy first!

[Church-Audio]

If it is a ground loop hum then it is going to be at 60hz. Unless it was recorded in Europe and then it is going to be around 50hz

Good call... never would have thought to add that!

fwiw

I had an issue last year with an acoustic show that I taped. It was a really quiet show and I ended up sitting in the back of the room right next to the power amps. (long story) The fans were really prevalent on my tape, so I used (don't cringe) the de-noise feature in Audacity, and with a little tweaking I was able to significantly reduce the white noise without adding a ton of artifacts from the "plug in". I can still hear the artifacts at times, but for me, it's less bothersome than listening to power amps.

If you're using SF8 I'm sure that you can find a de-noising plugin that should work well.

It could be at 60,120,180,240 because of harmonics but as the frequency goes up the amplitude should go down with harmonic distortion as you get further away from the center frequency.

[JackoRoses]

If it is a ground loop hum then it is going to be at 60hz. Unless it was recorded in Europe and then it is going to be around 50hz

Does it irritate anyone else when there is a ground loop and they don't even try to find it?
I just want to go up to the soundman and just "say will you fix that already?"
Drives me crazy fortunately I haven't had to deal with that too much recording. Only a few instances and they were bar bands so I guess it's to be expected?

[keyclick]

Its funny, tapers spend a great deal of time optimizing their 'signal chain' as it were, but still
have little or no control of over half of the actual total signal chain...

Noisy Guitar pickup > crappy beer soaked cables> Buzzy tube amp > torn speaker driver>
banged up Shure SM58> crappy beersoaked cable> Snake> Behringer Mixer > Ground Loops, digital noise, SCR noise from lighting system> Power Amp> Ratty Speaker Cables> Poorly placed, under powered Pa cabinets> Air conditioners/fans> noisy audience> Then to taper's gear!

[capnhook]

If it is a ground loop hum then it is going to be at 60hz. Unless it was recorded in Europe and then it is going to be around 50hz

Good call... never would have thought to add that!

fwiw

I had an issue last year with an acoustic show that I taped. It was a really quiet show and I ended up sitting in the back of the room right next to the power amps. (long story) The fans were really prevalent on my tape, so I used (don't cringe) the de-noise feature in Audacity, and with a little tweaking I was able to significantly reduce the white noise without adding a ton of artifacts from the "plug in". I can still hear the artifacts at times, but for me, it's less bothersome than listening to power amps.

If you're using SF8 I'm sure that you can find a de-noising plugin that should work well.

It could be at 60,120,180,240 because of harmonics but as the frequency goes up the amplitude should go down with harmonic distortion as you get further away from the center frequency.

I've had great luck with using Audacity, but you have to first google "Nyquist Plug-ins" in order to find a notch filter tool (filename is 'notch.ny').  Once you get the file, put it in your .../Audacity/Plug-Ins directory, so that it will then show up in Audacity's "Effect" tab.  Then, use the "Analyze>Plot Spectrum"  on a small section of offending audio, and note just how severe and at what frequency the peak harmonics are coming from.  Like Chris says, most cases they'll start at 60Hz, and then occur again at the harmonic multiples of 60Hz, only probably again not as severe as the peaks you'll see at 60Hz, 120 Hz, and 180Hz.  The notch filter tool will let you design a nice. high-Q frequency "trap" at your desired center frequency, and suck that "hum" right out of there.  I use this trick all the time to eliminate short-duration feedback squawks, too.

VIVA AUDACITY 

[hzgone]

If it is a ground loop hum then it is going to be at 60hz. Unless it was recorded in Europe and then it is going to be around 50hz

Does it irritate anyone else when there is a ground loop and they don't even try to find it?
I just want to go up to the soundman and just "say will you fix that already?"
Drives me crazy fortunately I haven't had to deal with that too much recording. Only a few instances and they were bar bands so I guess it's to be expected?

Drives me crazy!

[bluegrass_brad]

Does it irritate anyone else when there is a ground loop and they don't even try to find it?
I just want to go up to the soundman and just "say will you fix that already?"
Drives me crazy fortunately I haven't had to deal with that too much recording. Only a few instances and they were bar bands so I guess it's to be expected?

More often than not there is little they can do about it.  There have been plenty of times when Ive mixed shows where the ground loop hum was there all through soundcheck.  I would spend almost the whole time between soundcheck and doors trying to find it by using an AC lift on the gear, then using an XLR lift on the gear that doesnt have a built in lift.  All to no avail.  Or for another example, you soundcheck and evrything sounds fine.  Then when the show starts there is a nasty hum because they have plugged in some light or appliance that wasnt plugged in or turned on during soundcheck. If you are in a smaller place where they dont have a dedicated power leg used solely by the sound system then it happens alot.  Dirty power sucks.   Happens all the time. Bigger clubs, or the smaller ones that give a darn, have a dedicated power leg into a conditioner for nice clean power.

[Brian]

Its funny, tapers spend a great deal of time optimizing their 'signal chain' as it were, but still
have little or no control of over half of the actual total signal chain...

Noisy Guitar pickup > crappy beer soaked cables> Buzzy tube amp > torn speaker driver>
banged up Shure SM58> crappy beersoaked cable> Snake> Behringer Mixer > Ground Loops, digital noise, SCR noise from lighting system> Power Amp> Ratty Speaker Cables> Poorly placed, under powered Pa cabinets> Air conditioners/fans> noisy audience> Then to taper's gear!

awesome.  you must be a FOH eng. or have at some point.