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Digital recorder input volume-level question

 
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CP Heaton
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PostPosted: Sat Jul 13, 2019 12:10 pm    Post subject: Digital recorder input volume-level question Reply with quote

I recorded a 2/12-hour show from soundboard with Roland R-07 recorder. Input volume level 28. All settings (limiter, low cut) off. Analyze>Waveform Statistics showed 25,000+ instances of clipping. I did Effects>Amplify>99% and Waveform Statistics showed zero clipping. Would appreciate explanation of why this may have happened. Was my input volume level that close to ideal? I record only once a month. Will try level 27 next month. Apologies if I have asked this before. If so, have forgotten the answer. Thx. CP=
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Jim Edgar



Joined: 01 Mar 2010
Posts: 100

PostPosted: Sat Jul 13, 2019 6:28 pm    Post subject: Digital recorder input volume-level question Reply with quote

In digital recording, -0 dB is not "ideal".  We aren't "saturating tape." It is not good to be that hot. 

There is no reason to be pushing your headroom to that extent. I'm not familiar with the Roland, but if it has decent A/D converters and can record even in 16 bit/44.1 khz, you can work with peaks much, much lower. 


Simplifying greatly, 16 bit gives you -96 dB noise floor.  That means if you recorded the raw audio with peaks in the -12 dB range, you could easily increase it after the face and still not have noticeable system noise. 24 bit increases that to -144 dB. That gives you the headroom to absorb dynamics without distorting. 


All that the negative amplification step did was change the highest value. It no longer "clips" because the values are less than -0dB. The result could be unlistenable (due to the clipped audio you created in the record step). Digital distortion is a bad thing. 


If you are trying to recover that audio, I would work on a copy, then use a very light compression step (AUDynamicsProcessor) with a fairly high threshold and with the headroom curve just below 0 dB (for example Threshold = -13 dB and Headroom = -12.5.  Compare that to the result with your Amplify test.  First thing you'll notice is that the tops are not chopped off of all the clipped waves. 


That might save your audio. Might not. Depends how badly things were clipped at the initial record.  


With digital recording, lower levels are generally better. You can always bring them up later.


- Jim
Jim Edgar

VO: JimEdgarVoices.com | @jimedgarvoices | Source-Connect - jimedgarvoices


For audio/studio help: JustAskJimVO.studio | Schedule a session














On Sat, Jul 13, 2019 at 5:10 AM CP Heaton <heaton5@cox.net (heaton5@cox.net)> wrote:

Quote:
I recorded a 2/12-hour show from soundboard with Roland R-07 recorder. Input volume level 28. All settings (limiter, low cut) off. Analyze>Waveform Statistics showed 25,000+ instances of clipping. I did Effects>Amplify>99% and Waveform Statistics showed zero clipping. Would appreciate explanation of why this may have happened. Was my input volume level that close to ideal? I record only once a month. Will try level 27 next month. Apologies if I have asked this before. If so, have forgotten the answer. Thx. CP
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Jim Edgar



Joined: 01 Mar 2010
Posts: 100

PostPosted: Sat Jul 13, 2019 6:29 pm    Post subject: Digital recorder input volume-level question Reply with quote

Pesky autocorrect...

"Simplifying greatly, 16 bit gives you -96 dB noise floor.  That means if you recorded the raw audio with peaks in the -12 dB range, you could easily increase it after the face and still not have noticeable system noise. 24 bit increases that to -144 dB. That gives you the headroom to absorb dynamics without distorting."


should have been "...after the _fact_..."


- J



Jim Edgar

VO: JimEdgarVoices.com | @jimedgarvoices | Source-Connect - jimedgarvoices


For audio/studio help: JustAskJimVO.studio | Schedule a session













On Sat, Jul 13, 2019 at 11:27 AM Jim Edgar <jimedgarvoices@gmail.com (jimedgarvoices@gmail.com)> wrote:

Quote:
In digital recording, -0 dB is not "ideal".  We aren't "saturating tape." It is not good to be that hot. 

There is no reason to be pushing your headroom to that extent. I'm not familiar with the Roland, but if it has decent A/D converters and can record even in 16 bit/44.1 khz, you can work with peaks much, much lower. 


Simplifying greatly, 16 bit gives you -96 dB noise floor.  That means if you recorded the raw audio with peaks in the -12 dB range, you could easily increase it after the face and still not have noticeable system noise. 24 bit increases that to -144 dB. That gives you the headroom to absorb dynamics without distorting. 


All that the negative amplification step did was change the highest value. It no longer "clips" because the values are less than -0dB. The result could be unlistenable (due to the clipped audio you created in the record step). Digital distortion is a bad thing. 


If you are trying to recover that audio, I would work on a copy, then use a very light compression step (AUDynamicsProcessor) with a fairly high threshold and with the headroom curve just below 0 dB (for example Threshold = -13 dB and Headroom = -12.5.  Compare that to the result with your Amplify test.  First thing you'll notice is that the tops are not chopped off of all the clipped waves. 


That might save your audio. Might not. Depends how badly things were clipped at the initial record.  


With digital recording, lower levels are generally better. You can always bring them up later.


- Jim
Jim Edgar

VO: JimEdgarVoices.com | @jimedgarvoices | Source-Connect - jimedgarvoices


For audio/studio help: JustAskJimVO.studio | Schedule a session














On Sat, Jul 13, 2019 at 5:10 AM CP Heaton <heaton5@cox.net (heaton5@cox.net)> wrote:

Quote:
I recorded a 2/12-hour show from soundboard with Roland R-07 recorder. Input volume level 28. All settings (limiter, low cut) off. Analyze>Waveform Statistics showed 25,000+ instances of clipping. I did Effects>Amplify>99% and Waveform Statistics showed zero clipping. Would appreciate explanation of why this may have happened. Was my input volume level that close to ideal? I record only once a month. Will try level 27 next month. Apologies if I have asked this before. If so, have forgotten the answer. Thx. CP

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CP Heaton
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PostPosted: Sat Jul 13, 2019 11:19 pm    Post subject: Digital recorder input volume-level question Reply with quote

Thx for insights, Jim. I did record at 16bit/44.1khz and recorder has up to 24bit/96khz available. Will use 24bit next time. Any point in raising kHz (rookie question)? Initial recording apparently not badly distorted. Many instances of clipping but apparently not grossly clipped, to my ear.
Thx for specific recommendations re AUDynamicsProcessor. I will try.
Recorder has “Rec Mode” setting of 2xWAV-24bit. It makes 2 WAV recordings with one 20 input-volume levels below the other, IF the higher one is at least 42. I don’t suppose there is any point in using that feature, since the 42 will be uselessly distorted and I could use 22 alone if I wished.
I have been starting on the high side and working down to find a satisfactory input-volume level with no clipping. I will try working up from a lower level. Unfortunately I do recording like this only once a month, and I am on stage so cannot monitor what is happening.
Thx for the education. Fortunately for me, I have been getting acceptable results despite myself. CP

Quote:
On Jul 13, 2019, at 2:28 PM, Jim Edgar <jimedgarvoices@gmail.com (jimedgarvoices@gmail.com)> wrote:
Pesky autocorrect...
"Simplifying greatly, 16 bit gives you -96 dB noise floor. That means if you recorded the raw audio with peaks in the -12 dB range, you could easily increase it after the face and still not have noticeable system noise. 24 bit increases that to -144 dB. That gives you the headroom to absorb dynamics without distorting."

should have been "...after the _fact_..."

- J

Jim Edgar
VO: JimEdgarVoices.com | @jimedgarvoices | Source-Connect - jimedgarvoices

For audio/studio help: JustAskJimVO.studio | Schedule a session











On Sat, Jul 13, 2019 at 11:27 AM Jim Edgar <jimedgarvoices@gmail.com (jimedgarvoices@gmail.com)> wrote:
Quote:
In digital recording, -0 dB is not "ideal". We aren't "saturating tape." It is not good to be that hot.
There is no reason to be pushing your headroom to that extent. I'm not familiar with the Roland, but if it has decent A/D converters and can record even in 16 bit/44.1 khz, you can work with peaks much, much lower.

Simplifying greatly, 16 bit gives you -96 dB noise floor. That means if you recorded the raw audio with peaks in the -12 dB range, you could easily increase it after the face and still not have noticeable system noise. 24 bit increases that to -144 dB. That gives you the headroom to absorb dynamics without distorting.

All that the negative amplification step did was change the highest value. It no longer "clips" because the values are less than -0dB. The result could be unlistenable (due to the clipped audio you created in the record step). Digital distortion is a bad thing.

If you are trying to recover that audio, I would work on a copy, then use a very light compression step (AUDynamicsProcessor) with a fairly high threshold and with the headroom curve just below 0 dB (for example Threshold = -13 dB and Headroom = -12.5. Compare that to the result with your Amplify test. First thing you'll notice is that the tops are not chopped off of all the clipped waves.

That might save your audio. Might not. Depends how badly things were clipped at the initial record.

With digital recording, lower levels are generally better. You can always bring them up later.

- Jim
Jim Edgar
VO: JimEdgarVoices.com | @jimedgarvoices | Source-Connect - jimedgarvoices

For audio/studio help: JustAskJimVO.studio | Schedule a session












On Sat, Jul 13, 2019 at 5:10 AM CP Heaton <heaton5@cox.net (heaton5@cox.net)> wrote:
Quote:
I recorded a 2/12-hour show from soundboard with Roland R-07 recorder. Input volume level 28. All settings (limiter, low cut) off. Analyze>Waveform Statistics showed 25,000+ instances of clipping. I did Effects>Amplify>99% and Waveform Statistics showed zero clipping. Would appreciate explanation of why this may have happened. Was my input volume level that close to ideal? I record only once a month. Will try level 27 next month. Apologies if I have asked this before. If so, have forgotten the answer. Thx. CP



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