question about amplifier/PA hummmmmm

[tim]

Well, some friends of mine have a pretty good local band, and they play at various venues around a tri-county area. OK, so I went up town to hear them Sat. and one member and I got to talking on their break and he asked me so i thought I'd try to get some ideas here.

One place they play is an older brick building with everything that can plague an older brick building.

I'm sure the wiring is sub-standard and I dont' know if it has fluorescent lights causing fits or not. But all the amps and PH have a "hummmmmm" that they can't get rid of. The guitards amp hums the worst. Not totally obnoxious, but really annoying.

It seems that today's equipment(for the most part) doesn't have any provisions for a "reverse" switch on the amps, and with three-prong plugs it's kind of hard to do the old "turn-the-plug-around" trick.

Even with a reverse switch, I've seen instances where when flipped the hum only got louder.

The manager says all the bar/ kitchen equipment is in good order, but that's left to be seen.

So my question is, does anyone here know of any type of device/ power bar etc, that can help compensate for this type of a problem?

it's a good gig for them but event the patrons come and ask them "what's the hum?" They don't know, I don't know.

Any ideas?

Thanks!

[Blues Dues]

Jan 3, 2010 22:31:17 GMT -5 tim said:

Well, some friends of mine have a pretty good local band, and they play at various venues around a tri-county area. OK, so I went up town to hear them Sat. and one member and I got to talking on their break and he asked me so i thought I'd try to get some ideas here.

One place they play is an older brick building with everything that can plague an older brick building.

I'm sure the wiring is sub-standard and I dont' know if it has fluorescent lights causing fits or not. But all the amps and PH have a "hummmmmm" that they can't get rid of. The guitards amp hums the worst. Not totally obnoxious, but really annoying.

It seems that today's equipment(for the most part) doesn't have any provisions for a "reverse" switch on the amps, and with three-prong plugs it's kind of hard to do the old "turn-the-plug-around" trick.

Even with a reverse switch, I've seen instances where when flipped the hum only got louder.

The manager says all the bar/ kitchen equipment is in good order, but that's left to be seen.

So my question is, does anyone here know of any type of device/ power bar etc, that can help compensate for this type of a problem?

it's a good gig for them but event the patrons come and ask them "what's the hum?" They don't know, I don't know.

Any ideas?

Thanks!

You may need to experiment at the venue and with the owner's help to identify the source of the problem. Tell him that patrons are complaining and you want to see if you can cure it.

I think it depends on the source of the hum or 60 hertz noise.
If it's RFI radiating from lighting fixtures like florensent lights or other ballast type devices, you should be able to tell by simply turning the lights off temporarily. Older equipment in the place could also be introducing it either via RFI or on the AC line.
With the owner's permission and help, set up an amp with a guitar plugged in, turn up the volume until the hum is very noticeable and then, one by one, have someone turn off each circuit breaker in the power distribution box. See if any of them dramatically reduces the hum and then see what electrical device is powered from that breaker. Older electrical appliances and equipment can actually introduce 60 hertz hum in the power lines, particularly if they draw high currents when running.

www.federalpacific.com/literature/drytrans/10transformernoise.pdf

Another possible solution is to power the band's amps through one or two devices called an "Electrostatically Shielded Isolation Transformer". These transformers do not step the voltage up or down. They are used to isolate the load side from the primary voltage source. I'd check with a local electrician regarding the use of them. They need to be sized appropriately for your equipment's current draw.

Another possible solution may be to use a power conditioning unit. "Monster" and others build units that have both active and passive filters in them. They are typically used in higher end home theater or audio gear applications.

Here's some info on isolation transformers:
www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz

and here's some info for those of us that like screwing around with old, vintage guitar amps and have lived to talk about it:

www.instructables.com/id/Isolation-transformer-upgrade-for-old-guitar-amps/

RCE

[tim]

Thanks Rchard. That was fairly comprehensive and I'l be sure to pass the info along.

Tim

[papajohn]

Yeah all of the above. I've tried a million different solutions. Some work in certain places and some work in a few. If the place has flourescents lights, you're sure to have problems and if it's old, you're sure to have problems. I got fed up enough to go out and buy a Furman Power Conditioner. I don't recall the model number but I do recall it was about six hundred bucks. I can look it up if you need but I'm sure it is easily found online. It not only smooths out the signal and the noise but it keeps the power at a constant voltage. That made a huge difference with my bass amp. We plug most of our equipment into it and don't seem to really have any hum problem, but that could also be because I've lost too much of my hearing.
John

[brian]

I use a TDK 106 EMI filter that I purchased years ago. Basically, it is a line choke that is effective on some forms of outside noise. At a studio in an old brick building (second floor) in Weymouth, we spent months trying to find the culprit of an intermittant relentless hum, only to find out that the source was a defective 'starter' on a flourescent fixture in the store DOWNSTAIRS !!!! Good Luck !

[chuckochs]

All of the above suggestions are good ones, and illustrate the point that this type of noise can sometimes be VERY difficult to isolate, much less eliminate. The problem can emanate from the environment, or may be caused by problems within the bands rig. You have to eliminate one or the other.
A couple of brief additions: A condition known as "ground looping" can occur when more than one AC outlet is used by the band. This is a BIG no-no. Always plug the ENTIRE band into the same outlet. You may use distribution strips to plug in various amps, but ALWAYS plug the whole rig into the SAME outlet. This goes for the mixing board also, even if it is remote from the band. Use an extension cord! Besides the almost guaranteed hum that you will get if you DON"T do this, you are also creating a shock hazard. Ever get a shock when you touch your lips to the microphone?
Now-someone mentioned AC cords on amps. All modern amps, as well as other gear, come with 3 conductor grounded AC cords. Do NOT attempt to defeat this safety feature with adapters, or mods to the amp or cord. Death could be the result! If you own a vintage amp with a two prong cord, get it replaced by someone who knows what they are doing. If all the gear in the rig has proper 3 prong cords, and all is fed from one common AC source, than any other noises will be external to the rig itself. I once spent 2 days tracking down a similar problem in a cable TV studio in Falmouth going over their entire system before I finally found, and eliminated the problem.