Input Level Too Low

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Input Level Too Low

Permanent link to this post Posted by 3Zero » Sun Dec 27, 2009 6:01 am

Greetings --

With "all" (as many as I could find) levels 'cranked', I am still only able to reach a maximum input level of -10dB or so (as indicated on Audacity's input level meter). Can anyone offer any tips as to how to raise the input level another 6 dB or so?

I am transferring a (live) recording from a MiniDisc recorder to a PC running Vista via the line input on a(n internal) Sound Blaster Live! 24bit sound card. I am using the headphones jack on the MiniDisc recorder (no other option) to drive the input of the sound card. MiniDisc playback levels have been set to 'max' and line in gain/Audacity input levels set as high as they go as well.

In the past, I have used an outboard (home stereo) preamp between MiniDisc & sound card to boost gain further but am wondering if there are any other ways to increase the gain during the transfer besides adding another piece of equipment.

The recorded levels on the MiniDisc 'master' regularly reach -12dB with occasional peaks to -6dB (according to rudimentary MiniDisc meter), but overall level is low (no compression was used during live recording - I just set the input level conservatively).

Any thoughts???

Thanks!!
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Re: Input Level Too Low

Permanent link to this post Posted by waxcylinder » Sun Dec 27, 2009 11:19 am

Have you tried using Audacity's Amplify effect after recording capture?

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Re: Input Level Too Low

Permanent link to this post Posted by 3Zero » Sun Dec 27, 2009 5:26 pm

Yes - I have. My goal, however, is to maximize the signal level during capture. It seems to me that the greater the signal (without clipping), the better (just as in analog recording).

To illustrate the point, if one were recording an analog program with Audacity, it would clearly be preferable to set levels so that peaks were -6 or -3 dB rather than record with peaks of -50dB, followed by a whole bunch of after-the-fact amplification (via the amplify function). Recording at the max. permissable level ensures the most faithful transfer. This is my goal.
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Re: Input Level Too Low

Permanent link to this post Posted by waxcylinder » Mon Dec 28, 2009 12:03 pm

Actually, if you have your Audacity preferences set to the default 32-bit float then you should have plenty of headroom to apply amplification without deleterious effect onthe signal to noise ratio.

You can Export to 16-bit on Export (Audacity will do the downsampling for you) if you are making WAVs to burn to a CD.

See this article in the Wiki for more detail: http://wiki.audacityteam.org/index.php? ... _To_Use.3F

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Re: Input Level Too Low

Permanent link to this post Posted by 3Zero » Mon Dec 28, 2009 4:40 pm

WC

Thanks for your thoughtful reply. I hadn't thought of using the 32-bit setting but this is a good option now that I have switched to a more modern computer with a bit more processing power. This addresses at least one of my concerns - that being able to adequately encode/resolve low level detail in an already low volume signal. 32 bits should give me plenty of low level resolution.

If I were really picky, I'd pull out a quiet line level amp and boost the (analog) signal just before it hits the sound card. But for the purposes of this project, using the 32-bit setting in conjunction with the amplify function after transfer should do the trick.

I look forward to the day when I will acquire a decent portable machine capable of recording in the digital domain that will permit a direct digital transfer of recordings. I have my eye on the Sony PCM D-50 ...

Thanks again!
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Re: Input Level Too Low

Permanent link to this post Posted by kozikowski » Mon Dec 28, 2009 4:51 pm

<<<rather than record with peaks of -50dB>>>

Peaks at -50 means your show or transfer is broken. Peaks at -10 are perfectly normal for a television show whose "zero tone" (in the US) is -20. Even at 16-bit sound, performing a 6dB boost will not create problems. Noise floor on a 16-bit system is somewhere in the -80s or -90s, but PC sound cards tend to do much worse.

See, now if you were on a Mac, you could use the built-in S/PDIF connection and do it all digitally. No transmission loss.

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Re: Input Level Too Low

Permanent link to this post Posted by waxcylinder » Mon Dec 28, 2009 5:00 pm

kozikowski wrote:See, now if you were on a Mac, you could use the built-in S/PDIF connection and do it all digitally. No transmission loss.

Or if you have an Edirol UA-1EX external USB soundcard (or similar) connected to a PC - then you can use the digital SPDIF input on the Edirol and keep it all in digital :)

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Re: Input Level Too Low

Permanent link to this post Posted by steve » Mon Dec 28, 2009 6:14 pm

3Zero wrote:I am transferring a (live) recording from a MiniDisc recorder to a PC running Vista via the line input on a(n internal) Sound Blaster Live! 24bit sound card. I am using the headphones jack on the MiniDisc recorder (no other option) to drive the input of the sound card. MiniDisc playback levels have been set to 'max' and line in gain/Audacity input levels set as high as they go as well.

It strikes me as odd that you are getting a low signal. I would have expected that the headphone socket would be capable of going well above "line level". Is the original mini-disk recording particularly quiet?
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Re: Input Level Too Low

Permanent link to this post Posted by 3Zero » Mon Dec 28, 2009 8:03 pm

Thanks everyone - interesting discussion.

3Zero wrote:See, now if you were on a Mac, you could use the built-in S/PDIF connection and do it all digitally. No transmission loss.


Right - that would be best. I have the optional digital in/out module for my sound card, but alas, my MD recorder does not have a digital output.

waxcylinder wrote:It strikes me as odd that you are getting a low signal. I would have expected that the headphone socket would be capable of going well above "line level". Is the original mini-disk recording particularly quiet?


Yes, it is. I defeated the 'auto record level' feature and went manual. Since I can only adjust record levels while this particular MD recorder is PAUSED (not on the fly!) I purposely set the record level conservatively low. I don't think I 'went into the red' during nearly 3 hours of live recording, however, the average signal level is clearly on the low side. (No compression was used, etc.)

My goal here is to get the best possible result with the available equipment.

3Z
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