Trouble with 'metallic' sounding interference

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Hi all,

I'm looking for some help with a problem I am having with ripping vinyl to my computer. I have been doing this for the past year with no problems however after a recent house move and an upgrade to Windows 7 I'm encountering some irritating interference on recording. I can't hear it all the time and it only seems to affect mid range and bass frequencies. The best way I can describe it is a kind of metallic scraping or clanging.

The sound from my record deck is perfect. The interference only occurs after the sound has been processed by the computer.

I've tried changing the soundcard to an external one and the interference is still there. The external card was a cheap hong kong import but I hope this shouldn't matter. I tried shielding my graphics card too, but no joy. I am using pretty standard cables and don't want to splash out on fancy ones unless I'm sure this is the problem.

Prob best to let you hear for yourself, the first 30 secs or so of this record are just 4/4 bass drums and give the best example of the interference.

This is my recording - http://www.mediafire.com/?4jznac5slhlj435

This is how it should sound - http://www.mediafire.com/?eq9i10y8myj0e91

Any ideas on what is wrong much appreciated.

Cheers.
Steve

[Trebor]

IMO the "interference" is distortion caused by the signal being too high (too loud)...

Overload distortion and clipping on A2 (need to turn down the gain).png (44.88 KiB) Viewed 2437 times

There are hardware gain controls : an actual physical knob on your turntable.
And a software gain control : computer settings on your "USB Audio Codec" ("levels" slider).

Reduce the gain setting on the USB audio codec if this distortion did not occur with this hardware before the upgrade to windows 7.
You'll need to cut the gain by about 10db until the waveform does not quite reach the extreme +/-1 values, ( a.k.a. 0db), i.e. no clipping.

see ... http://wiki.audacityteam.org/index.php? ... ud_or_soft

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Thanks for reply. I gave it a shot and i'm pretty sure it's not the gain setting. It's there with the gain turned down too. Any other help welcome.

Thanks.

[Trebor]

A2 is severely clipped, look at the flattened peaks and troughs …

A2 is severely clipped.png (67.28 KiB) Viewed 2428 times

Something is turned up too high .

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Yeah I agree there. It is a loud recording but I have recorded about 250 LPs at the same level under XP and they display none of the metallic interference I'm getting now. With the gain turned down on the turntable output and at the control panel for the soundcard I'm still getting the metallic noises.

[Trebor]

I’ve just re-read your question,
I mistakenly thought you were using one of those USB turntables.
Sorry .

Make sure the output from your turntable is “line-in” and is plugged into the “line -in” socket on the sound card / computer.

You may have to select the “line-in“ option from within the software if your sound card only has one input socket.

If you feed a "line in" level signal into a "mic" socket on the sound card/computer the "line in" signal is too high and the sound is distorted as a result.

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No problem. Just to clarify, Audacity is set to line in and I have my record deck running into a gemini mixer then out its booth output and into the line in port of a soundblaster audigy on my PC. I've spent the past hour unplugging everything electrical I can find but this has had no effect. Is it perhaps possible that that the electicity supply itself is causing interference?

[billw58]

Read Trebor's post again and look at the waveform. Something is clipping somewhere. It is not interference. You were fine on XP but are having problems on Vista - that's the change that triggered the problem. Look closely at your Vista sound control panel settings. One of the Windows elves can help you with the fine points of that.

-- Bill

[billw58]

OK, I downloaded the two samples, and there is something very interesting about the distorted sample.

compare.png (49.36 KiB) Viewed 2406 times

First, one file is inverted compared to the other - I've inverted the "good" one to make comparison easier. I also lined them up time-wise.

I have View > Show Clipping turned on, but note that there are no red lines in the Audacity waveform display to indicate clipping. This says that the clipping is happening before the sound gets to Audacity.

This is not interference. Stop wasting your time unplugging things and thinking about shielding your video card. Find the source of the clipping.

-- Bill

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That makes sense. So my problem is somewhere between the sound entering the souncard and getting to audacity. Something I've noticed which would confirm this is that no matter what recording software I use I'm getting the same distortion. I'll have a good look at the soundcard settings panel tonight. Thanks.