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In Reply to: RE: How hard should I strive to get maximum signal? posted by Phil_in_CA on March 24, 2012 at 18:24:04
I appreciate your replies.
I have been within -6db on peaks and am recording at 24/96 that I convert to flac.
So far, I haven't heard anything untoward, but the thought stuck me this afternoon as I was recording some classical which goes from a whisper to a roar. The quiet parts got me to thinking...
Anyway, thanks for your comments and your time.
Phil and Muffin (RIP)
Follow Ups:
-48dB peaks in 24 bit is the same resolution as CD at full scale. Only those who are interested in "the loudness war trials / competition" need worry about trying to make up for the 'small mans' syndrome...
Go for best sound quality and use your volume control to determine listening levels.
"-48dB peaks in 24 bit is the same resolution as CD at full scale."
This assumes that the -48 dB digitization was done nearly perfectly. One might achieve an approximation to this if one were to start with a proper digitization and reduce it arithmetically, since this would get a result that was correct to within 1 least significant bit. However, if one were to feed a low level analog signal to an ADC the result would not be what you said unless the analog noise in the converter was below -144 dB. This is far better from any ADC that I've heard of. ADCs tend to have more noise than DACs and the best current DAC chips are at about 135 dB and this is under laboratory conditions. A complete DAC running in a box connected to a system will not have this performance.
I've seen 16 bit digital recordings with peaks as low as -30 dBfs that ended up sounding acceptable (if not excellent) after they were boosted digitally to a reasonable level. This will depend on the converters used, i.e. for decent results they would have to have no gross non-linearity at low levels and no loud hum, birdies or other spurious signals, and have been properly dithered. (At this level turning up the analog volume on the playback of the unboosted file would be a very bad idea. If there were enough gain to get reasonably loud music than any glitch might blow up some gear.) Of course there will be a lot of noise, but if the original was noisy to start with this might not matter too much. My comments applied to some recordings that I was given that had been recorded or transferred digitally at very low levels. They were what they were. If I had been doing a digital transfer and gotten these results I would have redone them after thinking carefully about how and why I had made such a mistake.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
You are right! I have notice that some CD's don't -fizz out- or lose sonic connectivity (whatever that means..read between the lines if you will) at low levels but some, especially ill transferred opera and classical / symphonic works certainly do. I am sure you have seen the reconstructed waveform of low level,(recorded in 16 bit) convoluted waveforms. The old Cool Edit pro (now Adobe audition) shows the reconstructed approximation, unlike Sony Sound forge.(which does not)
Since the advent of 24 bit being made available, there is no reason at all not to be using it for the recording, editing or mastering stage. I tend to set the recorders to peak around a -10 on the loudest of sounds.
"The old Cool Edit pro (now Adobe audition) shows the reconstructed approximation, unlike Sony Sound forge.(which does not)"
iZotope RX also allows such a plot. It is only an approximation as the peak factor depends on the reconstruction filter. With a perfect SINC filter there is no worst case bound for an infinitely long signal, but it can be over 10 dB for a CD track. (You wouldn't want to listen to such a recording even if it were reproduced "undistorted".)
"I tend to set the recorders to peak around a -10 on the loudest of sounds."
Sounds about right to me. Pink noise at -23 dB RMS (-20 according to the mathematically ignorant AES) peaks about at that level. This signal comes in around 0 VU according to the Nordic scale for digital audio, so there is comparable headroom here as with magnetic tape. The actual values vary a bit depending on the "crest" factor of the signal, which will depend on the musical instruments playing, the frequency response of the microphones and their location and the room acoustics.
I had one live recording where all but one of the peaks were around -15 dBfs that digitally clipped when a wind gust collapsed the performance tent. Sometimes there are worse problems than digital clipping. In this case the recording continued and a few minutes later the music resumed. :-)
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
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