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Old 02-03-2008, 10:37 PM   #1
marcus82
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Default sound card hum??? and how to eliminate

I'm pretty new to the audio recording world. Previously I had been working strictly out of Reason. So I've run into the first of many (i'm sure) adventures in audio recording.

Whenever I set up an audio track (stereo or mono) my track automatically meters at about 30 on the track meter. I can hear a faint humming, kind of like the hum i hear when i plug my guitar into my amp. I read something about a 60 cycle hum and I used ReaFir to elimnate noise at that frequency. This worked pretty well with reducing the noise.

Currently I'm running a computer with a stock soundcard, 756 mb of RAM, 2.2ghz processing speed, windows xp sp2, asio4all, um i guess that's enough info. Also as i'm using the stock soundcard i have to plug my guitar into the cpu with a 1/8" converter.

I'm assuming that a new soundcard will fix most of my problems (less hum, proper guitar i/o's etc.) but, how much of this hum should I expect to naturally exist on my audio tracks? What is the best way to eliminate this hum? Will i have to work to eliminate the hum from each and every audio track i record?

Just need some general help and guidance on this. If you give me a few keywords i can do a more thourough google search.

Thanks folks
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Old 02-04-2008, 02:55 AM   #2
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You should try using:
1) noise gate (ReaGate for example)

2) ReaFIR in substract mode (noise reduction): http://www.cockos.com/wiki/index.php/ReaFIR#Subtract)
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Old 02-04-2008, 03:19 AM   #3
Jack Winter
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There could be many sources to your hum/noise. First of all plugging straight into your soundcard is not optimal. Mainly because there will be an "impedance mismatch" which will change the tone of your guitar. The preamps on a built in soundcard are normally noisy and of low quality, so you will have a problem to get a good quality sound with good "signal to noise ratio". That being said I have a laptop where I do exactly the same, and then run the signal through guitarrig, and the result is totally ok for having some fun, but not studio quality.

Most likely the noise you have is picked up through your guitar's pickups. If you have a stratocaster or another guitar with single coil pickups, try chosing a configuration which uses 2 pickups, normally they will then function as "humbucking" pickups, and cancel out a large part of the noise. CRT monitors are normally very noisy, so try to step away from your monitor. Turning the guitar around so it faces against or away from the monitor will probably help too. If this is the problem and if the guitar is properly grounded then you will hear how the level of the noise lowers as you touch the strings.

-30dB on the input is very noisy (my inputs through a mixer is around -85dB), and probably means that you have cranked the gain on the mic preamp on your sound card. If you have a possibility see if you can't amplify the signal outside of your computer. See if your amp has a line output (do not plug the speaker output into your computer), or maybe you have an FX pedal or some such that gives out an ampliedfied signal. If you plug such a signal into the lineinput of your soundcard you should get a much better result.

Good luck and rock on,
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Last edited by Jack Winter; 02-04-2008 at 03:31 AM.
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Old 02-04-2008, 07:47 AM   #4
marcus82
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okay. thanks for the info. great job of explaining why i could possible bet getting so much noise. One thing though - my noise level is at -30db even before i plug in anyputs into the sound card. I guess that's simply because the sound card is cheap. I don't really see too much of an increase when i plug the guitar into the card.

I read another article that basically said that I will always struggle with noise no matter what. does this mean that when recording audio I will always have to take the additional step of noise removal? or is there some configuration i need to create so that all my projects automatically open up with some kind of noise reduction in place?

thanks
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Old 02-04-2008, 10:23 AM   #5
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You should setup your hardware correctly instead of tinker with effects.
For a guitar, you need an audio interface with high-gain input. Against ground hum, you need that: http://www.thomann.de/gb/palmer_pan_04.htm
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Old 02-04-2008, 11:05 AM   #6
Alistair S
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It's a laptop, so I have to ask - does the hum disappear when you unplug the power supply?

Ground loop issues with laptop power supplies are VERY common, though this usually comes up when you have other gear involved.
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Old 02-04-2008, 11:12 AM   #7
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stock soundcard is a terrible idea for any kind of multitracking application. that'd be like trying to race a non-modded civic dx.

get at least a m-audio mobile-pre, emu 0202 or lexicon alpha as a minimum. usually you can find stuff like that at a local consignment shop for dirt cheap ($80 or so - which makes for a great deal).

anything that can work with both high and low-z inputs are fine. if you're ridiculously cheap and only need to record guitar you could pick up something like this:
http://www.zzounds.com/item--MDOJAMLAB
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Old 02-05-2008, 04:24 AM   #8
Jack Winter
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I just tried my laptop, and the noise is indeed at about -30dB, still allows me to have some fun but hiss is noticible and it won't make any professional recordings. I have only mic input, no line input on the laptop so can't try that one. On the desktop I tried quickly to check, but I don't seem to able to access my builtin soundcard, and I am too lazy to muck around too much with it. Should be better than -30 dB though... My external RME multiface hooked up to a mixer gives me somewhere between -80 and -90 dB. Huge difference. One thing though, on my laptop I had only hiss, with some clicks and no hum. It doesn't disturb me all that much. If you have hum, then there is something else wrong...

If you are serious about recording, the only viable solution is a better soundcard. To chose, ask yourself what you budget is. How many tracks do you need to record at once. Most people manage 2, a guitar and vocals, stereo output from a keyboard or FX unit, etc. Do you need builtin preamps and phantom voltage and an instrument input, or do you combine the soundcard with a small external mixer (nice to have). What kinda interface USB/Firewire/proprietary. Then what OS do you wanna use it with. It gets complicated quickly If you only need 2 channels you can probably buy a pretty decent external solution for not so much money which allows you to plug in a guitar and a mic, and allows you to carry it with you. Will give you much more satisfactory results.

You can also try with noise reduction techniques, but it will never give you a satifactory result. It will always degrade the results...

Best of luck,
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