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.
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.
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