Post by yves on Jan 24, 2015 5:20:55 GMT -5
first, i'm not sure about "the ringing is caused by the signal is band limited". the audio note CD-4.1x cd player which doesn't employ over sampling and digital filtering looks good on time domain :
even a cheap, $60 nos dac MUSE Mini TDA1543x4 does look good on time domain : archimago.blogspot.com/2013/02/measurements-muse-mini-tda1543x4-nos.html
here is another effect of different digital filters to impulse response : www.stereophile.com/content/dcs-vivaldi-digital-playback-system-measurements
(note that beside ringing, digital filter also affecting phase linearity like analog filter)
as for square waves which is in the frequency domain, i think most will agree that nos dac doesn't measure good on frequency domain, but they DO look good on square waves : www.dddac.com/dddac1794_test_specs.html
i'm not sure either about "the ringing is at frequencies you won't hear". the impulse response from ps audio dac is about 0.1 ms and the ringing is about 0.4 ms each way (before and after). 0.1 ms = 0.0001 s. with f = 1/T = 1/0.0001 = 10000 hz = 10 khz.
second, agree that all dacs use some filtering, wether it's digital or analog filtering. with EVERY kind of filter, we want the good thing to pass and the bad thing to go away. but unfortunately most of the time, the bad thing also pass. it means there are also some side effects. BOTH digital and analog filtering have its weakness. what i found does not make sense is applying that filter at high frequencies WOULD NOT affecting lower frequencies in the audible range. why ? because those filters are actually wide bandwith low pass filter. more steep filter will have more side effects. and like you said, even if the dac doesn't have filtering most pre-amps, power amps and speakers has their own filters. even our ears too ! www.metrum-acoustics.com/Design%20Philosophy%20Metrum%20Acoustics.pdf
third, i'm not saying that DSD avoids filtering. like you said before, in a pure DSD process, mixing and equalizing in DSD format is impossible. so in a true DSD playback, the filtering is done in the analog domain (not using digital filter). but unfortunately (just like in that weiss' white paper), some DSD players are not pure DSD like the ones who use Sabre ES9018 chip. they converted DSD to PCM first then applying digital filter which make it not a pure DSD and lossy conversion.
The Sabre ES9018 chip does *not* convert DSD to PCM first. What it does do is it uses a Delta Sigma Modulator that is 6 bits wide, and the reason why it does that is because of the simple fact a Multi-Bit Modulator (MBM) can achieve greater accuracy than a 1-bit modulator can, *regardless* of whether the DAC is playing PCM or DSD. So the industry has almost completely moved away from 1-bit modulators for playback of both PCM *and* DSD, i.e. almost every modern DSD capable DAC uses filters in order to actually, contrary to popular oldschool "DSD belief" of course, *improve* accuracy.