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Although some of my equipment uses unbalanced leads, in our main venue we have no "hum". . . using the same equipment, (leads etc), but adding lights and finding less power points (and therefore dasiy chaining extentions) we had that dreaded hum. Can anyone suggest why and possible solutions. . . and on a sidenote, if the venue provides faulty wall sockets, and like most we don't have a contract (and even with a contract) where do we really stand if we refuse to play?

I had a hum last Saturday, couldn't think of what had changed, as this is the same venue, and I hooked up my equipment the same way I always do. So, what I did was put a 3 to 2 prong adapter on one of my powered speakers, and VOILA, no hum. I run the whole night without a problem. As far as I know, that shouldn't hurt my equipment, all I know is that it worked. This week, I went and bought 2 more adapters, just in case I need them.

Rosario

If you have to do that on a powered speaker that means you only have one inner conductor. You need two for a signal ground. If that cable was working before one conductor came loose. You can run them with an adapter but I dont like to in case of a power surge or spikes on the line such as coolers kicking on and off.

You can refuse to use an outlet if it is faulty. What I would do is agrree to use it for that night with the understanding it would be fixed and in the meantime they are liable for damage to gear. It would be better to run a long extension cord to a good outlet. I have run 300 feet out at the lake with no problems.

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Thanks for the advice karyoker. I have extension cords with surge protectors on them, I'll run one of those next time, and hook my powered speaker to that.

Rosario

Here is a diaphragm out of a JBL EON I replaced. If you notice where the yellow wire hooks in the lighter color band is the coil. The windings are very very small guage.

coil

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Get this:

http://www.furmansound.com/product.php?div=01&id=PL-8C

or this

http://www.furmansound.com/product.php? ... =PST-6_PRO

Then run extensions to your speakers.

It's been my experience that the mysterious hum that seems to come and go can usually be traced to a Dimmer or any other type of Rheostat, Fluorescent Transformer or even a Neon Sign, in the bar that may or may not be in use on any given night. I've also found that faulty shielded cables that will either cause or magnify the same condition. Unlike most here, I isolate each of my individual rack units from the rack itself and each other to help prevent ground loops.

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All of my equipment is new. I use Whirlwind speaker cables, the only difference that there was when I got the hum, was that all of my setup is plugged into a surge protector, with battery backup. One speaker was plugged into a power strip with surge protection, but one speaker was plugged into a wall outlet directly. When I got the hum, I put the two prong adapter on the speaker that was plugged into the wall, and the hum stopped. I have another power strip with surge protection that I will use this Saturday for that speaker. I'm hoping that the problem will be solved that way. If I have to still use the two prong adapter, can my speaker get damaged, as long as it is on a surge protector?

Rosario

In essence when you use a three to two prong adapter all your doing is removing the ground from the circuit, which is never a good idea. It would be better if you can find a way to power both of your powered speakers from the same outlet (or another outlet that is known to be on the same circuit). If you are running equipment from two or more separate power receptacles, especially if they are widely separated and the building wiring is old or not up to spec, there may be residual 50 or 60 cycle voltage present between the two alleged ground connections. The residual will be small, in the order of millivolts, unless something is seriously wrong with the building system, but it may be large in terms of audio signals. If all else fails it would be better to disconnect the ground on one end of the XLR cable you are running to your speaker instead of lifting the electrical ground.

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Quickness of mind will deceive the eye

I was getting a humm from one of my venues. I figured out it is the Neon Lights. I was plugged into the same outlet the Neon Lights were. The lights transformers have to step up to a high voltage to illuminate the lighting fixtures.

I moved to another outlet without any Neon Lights, Beer Signs, and the humm is gone.

In a couple of private parties I have got the humm. Once from being on the same circuit as a fish tank, and once on the same circuit as a refrigerator. Moving the power fixed both problems.

Felix the KJ

Very true, some Neon Signs need the voltage stepped up to 15kv to function. I don't think the OP is even sure what is causing the Hum as of yet, be it a ground loop or outside interference at this point. Of course determining the cause is important to effect the cure. There are numerous variables when it comes to electricity and audio signals, but with some deductive reasoning and some trial and error they will find it. My last little noise maker was tracked down to one little foot and a half long patch cable.

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Quickness of mind will deceive the eye

You are correct. . . I don't know what caused it, just asking more for ideas. It's unlikely that I'll be back in that venue. . . . but more than likely that'll i meet another hum.

Can daisy chaining most likely to cause it? or the fact we only had two plugs and a lot of equipment?

Neither of those scenario's should cause a line noise problem, unless of course there is a faulty cable involved. I suspect there was something else on the circuit that you were having a noise problem with. Just a guess, it's kind of hard to tell from here.

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Quickness of mind will deceive the eye

Hi Marble,

I have a large computer battery backup power supply mounted in my rack. Everything important is plugged into the backup supply, and everything else is plugged into the surge side of the backup power supply. It adds about 12 pounds to the rack, but adds thousands of dollars in peace of mind!!! If I lose power I have several minutes to propely shut down all my euipment. This unit also acts as a humm suppressor because the equipment is actually running on a battery, and not a/c current from the wall outlet.

mrmarog (retired engineer for Hilton Industries & Mallory Electronics capacitor design)

Is this an excellent idea?? How many other computer kjs are using battery backups? I'm going that route soon.....

A UPS would be great for graceful shutdown for your PC. However there are many other, better, line conditioners out there. The Furman line conditioners cannot be beaten on a price/performance basis IMO.

s'cuse while I get comfy on London's lap...ahhh thats better...now I had the same prob...and always blamed the dimmer in the restaurant. Actually the prob was...I plugged the speaker over the other side of the room into a different socket to the rest of my equip. Try making sure that ALL your equip comes back to the same socket (I run a multiboard off one socket) it may mean that the speaker wayyyy across the other side of the room needs an extension cord and a lot of tape, but see if that cures the prob...it did for me

LL will you stop squirming...and what's that in your pocket?

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