Old wiring= 60 cycle hum= I go nuts


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I've been using my apartment as a studio. I'm lucky enough to live above a vacant store. Plus my roomates are either in my band or very tolerant.

Anyways, it's working out beatifully except for horrendous hum. Mostly from the guitars & bass but sometimes it comes through the monitors too. Yes, my guitars have single coil pick ups but I sheilded the shit out of them and don't have this problem elsewhere. I've read some stuff on this and heard that the ancient wiring in my apt may be the culprit. But I haven't read why, or what can be done about it, short of tearing out the walls and re-wiring the joint. Obviously, with the old wiring, there are no grounds. It occured to me that this might be the problem and perhaps a temporary ground could be set up. I can't see how it could hurt but I'm wary of trying it without some confirmation.

There IS one outlet with a ground. I checked it out w/ a voltmeter and did find current from the ground to the hot. I don't trust that it's actually properly grounded though and I don't know how to tell. When I used this outlet to plug my amp into, there was no improvement at all.

Please help if you can. Otherwise I'll go nuts.
Just a piece of advice: Speaking from experience trying to work on the electrical system in a house, if you aren't an electrician I'd suggest hiring one to come out and tell you what you've got, and what can be done about it. I learned the hard way not to mess with electricity, and it's worth $200 or so everytime I move into a new place to have an electrician come out and run a new circuit or rewire stuff when necessary.

Maybe it's possible to run a new circuit from the switchbox with better, more modern wiring and put some outlets on it, separate from the rest of the apartment. The old wiring could stay, and you would have all your equipment for recording isolated from other electrical devices in the house. I'm not all that sure how the switchbox would be setup in an old building like that, so you might not be able to improve anything without upgrading the entire place. Again, an electrician could probably tell you in about 15 minutes if any of this is possible.
One interesting source of line noise is
from common light dimmers. You know the slide or rotary type that make bulbs dim or bright. They all introduce "Hum" and the only way to rid of it is to lose the dimmers.

Just thought I'd mention that because I had that very problem and an elctrician informed me of this anomolie.
I rent, so I can't really do much to change the wiring. There are no dimmer switches in our apartment. It occurs to me that the vacant store below might have flourescent lighting. They are very slowly turning it into a coffee shop and I think they sometimes leave it on.

Nope. I just checked. The lights are off and the hum is still there. I could live with gating it, except that it's so bad that it becomes clearly audible during quiet or sustained parts. Sometimes I like to use alot of fuzz and then I'ts nearly impossible to gate because the headroom between signal and noise is almost zero!

Anyways, I'm not an electrician but I am a maintenance guy so I do know something about it. At least I could probably set up a common ground for everything. I just don't know if that would help.

[This message has been edited by Ptron (edited 04-24-2000).]
Try lifting the ground wire on all balanced connections in your audio path at all the outputs of the equipment. Leave them at the input. This will still allow any interference on any cable to get to ground of the next device in line, plus, it removes the potential of ground loops, which is why you have a 60Hz hum. Create one cable that has the ground lifted at one end and go through your whole signal path to see if it is just one piece of gear that is causing it. If it is not just one piece, start modifying the cables to remove the ground at the inputs. You don't really need to do this though on any mic to preamp connections at the mic is not really grounded except to the preamp, so, it does not have another potential ground except someone touching it.

If this does not remove the problem, you have at least one piece of gear that is having troubles.

60Hz hums are the result of at least one piece of gear having to ways of getting to ground. Since you are using 2 prong outlets, you have removed any possibility of it being in the AC per se. Some audio components ground differently then others, although, most new gear follows the same grounding scheme (finally! this was not the case even 10 years ago) so usually, new gear will not have any issues. Older gear in the audio MAY be the problem.

Anyway, try the above and it should go away.

Thanks for the advice Sonusman but I think I may have misused the term "60 cycle hum". The buzz I'm getting through my monitors comes and goes and is relatively minor. Also, It doesn't show up in the recordings so might be a power amp thing.

It's really the hum from the guitars and bass that's giving me a headache. I've seen those devices that claim to "condition" the power. Is this the kind of situation they're for?
What kind of amp do you have for monitors?

Power conditioners are really no big deal. They make sure that sudden spikes in the voltage will not mess up your components to the degree that they are capable of. Nothing is full proof though. But generally they do the job.

You may be thinking of a Line Voltage Regulator, which "captures" voltage between a minimum and maximum and creates a constant. On the Furmen Line Voltage Regulator I have, if the incoming voltage is between 95 and 140 volts, it will output a constant 115 volts. Cool, and very good for digital recording. It also "conditions" the power, meaning handles voltage spikes. It is an expensive little box, I paid about $470 3 years ago for mine.

Next time the hum comes back around, see if a refridgerator or furnace is coming on. When it goes away, see if either turned off.

I asked about the amp because cheaper amps sometimes have thermal isssues that can cause hum. I have found that many cheapo amps like the Samsom stuff are very prone to this.


[This message has been edited by sonusman (edited 04-25-2000).]