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vinyl to digital: proper recording levels to minimize noise

 
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mattspringer



Joined: 29 Apr 2008
Posts: 11

PostPosted: Mon Jan 03, 2011 5:58 am    Post subject: vinyl to digital: proper recording levels to minimize noise Reply with quote

I've got a bunch of vinyl recordings to digitize for ultimate mp3 conversion, and I'm trying to figure out the best way to set recording levels to avoid both a hum and a hiss. My turntable is part of my home stereo system, and I am connecting a microphone cable from the headphone jack of the stereo receiver to the line-in port on my MacBook Pro.

I'm trying to set recording levels to have the loudest parts of the music occasionally in the yellow. I can do this either by adjusting the output volume of my stereo or by moving the gain sliders of the Amadeus Pro recording information window. My problem is that I'm dealing with a lot of background noise, and in some cases, the sample/suppress noise feature takes care of it; but in other cases, the noise is so loud that denoising degrades soft sections. If I turn up the stereo receiver output volume, the hiss (groove noise?) gets too loud and I can hear it while setting the levels; but if instead I turn up the gain sliders, I get a hum (ground-related?) only in one of the two channels that I DON'T hear while recording, but do hear when playing back the recording.

Clearly, I could just keep both volumes low enough to minimize noise and normalize the recording upwards in Amadeus. However, in some cases, this will involve quite an amplification, and I'd rather just figure out the source of the hum and get rid of it. I get the hum whether or not the record is playing, and its volume is unaffected by changing the output volume of the stereo, so even if the volume is all the way down, I get the hum. If I record while the cable is not plugged into the jack, then I don't get the hum. The hum occurs regardless of whether the laptop is using battery or power cord. The 3-prong electrical cords of the turntable and the stereo receiver are both plugged directly into a power strip.

Any advice would be greatly appreciated!
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rfwilmut



Joined: 17 Nov 2006
Posts: 255

PostPosted: Mon Jan 03, 2011 9:41 am    Post subject: Re: vinyl to digital: proper recording levels to minimize no Reply with quote

From your description the hum is in the headphone output circuitry (if it was a ground loop it would disappear when your ran the laptop on battery) and you are unlikely to be able to get rid of it. Does your hi-fi not have tape output RCA (phono) sockets? - this would be a better place to connect. If you have to use the headphone output you should turn the hifi up as loud as you can without causing peak distortion and turn the input level in Amadeus down so that the loudest sections just hit yellow. You'll need to do some tests: if you get distortion you'll need to reduce the hi-fi level. This way, since the hum is constant, you'll get the best difference between the audio and the hum.

The groove noise will be constant relative to the peak level however you set it. While there are hiss reduction facilities in Amadeus, you will get better results by using ClickRepair and Denoise:
http://www.clickrepair.net/
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mattspringer



Joined: 29 Apr 2008
Posts: 11

PostPosted: Mon Jan 03, 2011 4:50 pm    Post subject: Re: vinyl to digital: proper recording levels to minimize no Reply with quote

Thanks, that makes sense about the headphone circuitry. Yes, I could try what you suggest, which I assume involves taking a cable that has two RCA plugs at one end and a stereo minijack at the other, and plugging it into the back of the receiver. I'll give it a try tonight and will let you know. Cheers, Matt
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rfwilmut



Joined: 17 Nov 2006
Posts: 255

PostPosted: Mon Jan 03, 2011 5:10 pm    Post subject: Re: vinyl to digital: proper recording levels to minimize no Reply with quote

mattspringer wrote:
...which I assume involves taking a cable that has two RCA plugs at one end and a stereo minijack at the other, and plugging it into the back of the receiver


Exactly. That's much more likely to give satisfactory results.
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mattspringer



Joined: 29 Apr 2008
Posts: 11

PostPosted: Thu Jan 06, 2011 10:50 am    Post subject: Re: vinyl to digital: proper recording levels to minimize no Reply with quote

It's the oddest thing: I hooked the dual RCA plugs to one of the pairs of tape deck output jacks in the stereo receiver, and there was no hum when I tested it out, but when I did my first actual recording in that configuration, there was yet another hum of a different quality when there was no music playing. I was trying all sorts of things to get rid of it, and then accidently turned the stereo receiver's "recording source" knob to "tuner," which resulted in a loud pop and my sound level meters going to red; I turned it back to "phono" as the recording source where it had been before, and now the hum was gone! I got a great recording out of it with no need for any kind of denoising. I have no idea what happened, but the ultimate results were good.
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rfwilmut



Joined: 17 Nov 2006
Posts: 255

PostPosted: Thu Jan 06, 2011 11:38 am    Post subject: Reply with quote

Muck on the switch contacts, possibly.
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