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anonymous 9 July 2004

Every studio has a certain amount of hum-problems, the more gear the more problems, I suppose.. Especially combining balanced and unbalanced gear seems to generate some problems, you may have outside factors that give you hum and probably a million reasons more. I've been trying to get my studio as quiet as possible for the last days but a couple of (very small) problems remain. I hereby welcome your best hum-elimination tricks and tips.

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KurtFoster Fri, 07/09/2004 - 12:17

Upgrade / replace all the wall fixtures and wall switches. This is a cheap fix for hum plagued rooms. Often hum is being generated by poor contacts which create arcing, thereby inducing static and hum into the lines.

Check to make sure all your wall recepticals are in phase with each other..

Try to isolate all your audio gear and run it off of a single common electrical circuit. In commercial buildings it is easy to get an electrician to go into the main panel and place all the wall plugs that power your audio gear onto the same leg / circuit. Try to have appliances, lights and hvac run off a different leg if at all possible leaving only audio on one leg ...

The key is to insure that all your audio gear only has one common path to ground ... If you have to, you can star ground the system by disconnecting all the equipment grounds and tying them all together and then running that lead to one physical ground, like a stake driven well into the earth.

jonyoung Fri, 07/09/2004 - 20:08

Kurt's advice about a dedicated circuit & ground is right on the money. Also, check all recepticles and switches to see if the wiring is to the "stab-in" slots on the back. Change them to the screw terminals if so. Any dimmers in the house? They could be on the same circuit as your gear power source, even if in a different room or on a different floor. Either lose them or upgrade. If you have a DAW, sometimes the power supply in the computer will generate noise to the soundcard outputs. Unfortunately, the list is almost endless :? . Good luck.

anonymous Sat, 07/10/2004 - 02:05

Thanx for the good advice, though I got most of that covered and it´s fairly quiet now. I had one ugly hum that I just could not figure out and started powering up the studio piece by piece. And it came from an AD/DA converter when it was powered up...a high end converter supposed to be... Then I realized it has an external power supply and when I started moving the supply around the hum faded in and out as I was moving it ! Found a spot where it´s quiet and, voilá ! Why it´s so sensitive remains a mystery.., anyone ?

anonymous Mon, 07/12/2004 - 13:24

Seems like you've got it resolved, but I had an interesting experience worth mentioning. I have dedicated power to my room with a short run from the main ground. I've got hum-frees on all my rack gear...and I was still having a lot of background noise in the lines.

Solution! I got rid of all my surge protected, flitered power strips and use simple 12 guage outlet strips from the hardware store. Nothing but outlets wired in a row for rooms that aren't pre-wired. All the problem went away. When I leave, I unplug them. Other than that,itsbeen hastle free/noise free power.

anonymous Tue, 07/13/2004 - 01:52

Wow! No surge protection. I have everything with a hard drive (Roland 2480, Masterlink, etc) plugged into APC back ups which guarantees a solid 110-120 current with no sags or surges, and lets me shut down everything properly if there's a power outage.
I've never had any hum problems, but as mentioned I also rewired
all outlets and made sure it was all on one circut. Also, never plug a
surge protector into a surge protector to increase your number of
outlets. That could mess you up as well.
http://www.karynwhittemore.com

Thomas W. Bethel Tue, 07/13/2004 - 05:37

Hum can come from various sources. The one thing you do not want to do is to lift the grounding pin on your equipment to get rid of the hum. It is dangerous and can result in someone getting injured or killed.

There are some very good resources on the web dealing with hum and grounding.

http://www.hometheaterbuilder.com/issue/602_ground_loop.htm
http://www.cinemasource.com/articles/gnd_loop.pdf
http://www.epanorama.net/documents/groundloop/index.html
http://members.tripod.com/~AMN92/hum.htm

and my favorite for all kinds of information including grounding and signal interconnects

http://www.rane.com/library.html

As to Kurt's reply. In the U.S. the National Electric Code defines the "phase" of outlets. Black to Brass - White to Silver - Green to ground. These have to be the way things are wired UNLESS you have two pin receptacles with no indication of hot and neutral (in such a case you should have an electrician put in the proper outlets with ground.

We spent a good deal of time and money on our electrical setup in our mastering studio. All of our equipment is isolated from the incoming power by isolation transformers and all of our computers are on battery backup and power conditioners. All the wiring for the audio is on one leg and any other devices that could cause noise are on the other leg of the 220 service. Our lightning dimmer is a variac/autoformer and generates no noise. Any wall warts are physically isolated from the equipment and everything is run balanced with no unbalanced circuits. Our star grounding terminates in a 6 foot copper stake driven into moist earth and all ground lines are 10 Ga or better.Our noise and hum levels are very low and we are very careful when installing new equipment that we do not compromise this setup.

Best of luck on your setup. Sounds like you have most of the problems licked.

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