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In Reply to: RE: Don't trust everything you read on this forum posted by Christine Tham on July 13, 2007 at 20:46:52
DSD, if you can exceed it's massive headroom, clips softly, like tube amps ... no hideous tearing noises.
Dr. S.
Follow Ups:
Yes, DSD behaves differently than PCM when amplitude exceeds full scale. But the noise increases exponentially, together with a corresponding loss of detail. And you end up with a bitstream that is illegal to master onto an SA-CD, so you need to reduce levels, which means processing the signal.
You just aren't manacled by the absolutely no clipping mandate of PCM.
The Good Doctor
I seem to recall he said it was better to record under -3 to -6dB below full scale, otherwise DSD loses definition at the top end.
whether or not DSD behaves better at higher than 0dB FS is kind of a moot point, because the signal is illegal by Scarlett Book standards, and if you try to play it back on a DAC, the signal may clip anyway (because the Vref+ and Vref- is still set at fullscale, so the DAC is physically incapable of generating higher than fullscale voltages).
0dBfs = -6dB 'SACD' or another way; The nominal maximum level for an SACD is 6dB below PCM's absolute maximum of 0dBfs.
The maximum legal limit of an SACD's amplitude is +3.1 dB SACD or -2.9dBfs PCM. The mentioned 'Scarlet Book' also sets limits for ultra-sonic noise and DC offset.
What I actually said is that I hear problems with pushing levels up to the +3.1 maximum level and prefer to keep my maximum to 0dB SACD, with occasional peaks going up to about +1.5 dB SACD.
Really fast transients (essentially inaudible) are not really the problem; it's when the peak duration is around 200 samples or longer that it starts to become noticeable.
There is nothing gentle or soft about signals that exceed the +3.1 level; it's illegal because it is gross over-modulation of a system that behaves best with 50% modulation (-6dB), but will tolerate 76% modulation (-3.1dB) - just don't spend any 'musically significant time' at that latter level...
Now, if you'll excuse me, I have to go and finish making someone's CD really $%&$%ing loud.
:)
Graemme
NT
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