Cheesy Sound Cards, Recording, Hums & Buzzes

[John]

I can always hear a humm/buzz in the speakers (even when you're not playing back or recording anything). I know that you can get interferance from things like power and lights, but I think it's comming from something (maybe the fan) inside my computer.

Is there anything I can do to get rid of the humms & buzzes when I record?

[Rexx]

It could be many things, ground loop hum is a common problem.
I often rid ground loops by lifting the ground on some devices while flipping the ac connection. Experiment until the noises are minimalized.

Try moving your speakers around (probably not the solution but it can't hurt to try)

Poor quality cables and connectors can lead to noise.
Draping audio cords over ac lines isn't helpful.
Light dimmers are rheostats that generate lots of noise (too be avoided)
CRT type monitors can cause hum in guitar pickups and cheapo mics.
If you have headphones it's a good idea to check various headphone outs that exists on your synth, mixer, soundcard... Just to isolate where the buzz hum is coming from.
Try disconnecting the input connections to your soundcard to see if it is your computer.
As you can see it's a process of elimination

[Enigma™]

also make sure your gain isn't too high for input levels on the soundcard as well - Try muting different channels in the mixer to see what it's coming from. Sometimes my Mic level jumps and causes the very thing you mentioned. Muting does the trick

[Spacehog]

I often rid ground loops by lifting the ground on some devices while flipping the ac connection. Experiment until the noises are minimalized.

It should be pointed out that the ground Rexx is talking about lifting is (I hope!) the audio ground (ie the shield on the audio cable) not the mains ground, which you should never lift to avoid potentially FATAL consequences. Don't screw with AC at all, even at the namby-pamby voltages you deal with in the US, a bit of hum is nothing when you're in hospital for weeks after a bad electric shock / burn.

As an aside, you can get clip-on ferrite collars that you can clamp round the end of cables that are designed to reduce RF interference. Most specialist electrical stores should sell them (I know we do in the UK). If you do think it's coming from your PC though, keep cable lenghts as short as possible, and you can isolate your PC from your audio circuit by feeding it through a transformer or a DI box (albeit a bit of an overkill method!) which would probably solve the problem.

Martin

[John]

Thanks for the ideas. I'm going to try them out this weekend.

- John.

[Cary]

More on ground looping...
Make sure everything is plugged in on the same circuit (not nessasarily the same outlet) as looping is caused by a difference of potential between multiple grounds.
Also check other stuff like your modem/cable modem connection. Different grounds from different services can cause looping. I have a very slight hum in my gear caused by a ground loop from my cable modem. One of these days I will get around to fixing it.

http://www.passlabs.com/pdf/ground-loops.pdf

[John]

Thanks again for the great sugestions.

Well I didn't wait for the weekend. I found my problem at lunch today.

I had a cable with a 1/4 inch stereo jack plugged into my headphone out on my keyboard and the other end was a 1/4 inch stereo jack pluged into an adapter plugged into the 1/8 inch line-in on my computer. Something (probably that adapter) was causing the humm/buzz.

I replaced the faulty cable setup with RCA's plugged into 1/4 inch jack adapters plugged into the mix-outs on my keyboard then that went to an 1/8 inch jack plugged into the line-in on my computer.

Big improvement. Thanks again, John.