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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: RE: Tube DAC's ROCK posted by dazzdax on February 15, 2009 at 14:29:36:
"If I understand the explanation correctly, DAC chips don't have the biggest impact on sound quality but the filters that are being used to cancel the high frequency noise artifacts?"
The chips do have the biggest impact on sound quality, in my opinion, because the filters are already in the chips (unless an upsampling chip is used prior to the DAC chip, in which the upsampling chip's filter takes over), and are not exactly optimized for the best sound quality possible. (Although the new "minimum-phase" filters recently introduced is a giant step in the right direction, in my humble opinion.)
The filters themselves block, to varying degrees, the ultrasonic reflections, and push out the first alias much farther out into the ultrasonic band. They're used mainly because they're effective at blocking out the initial alias components (prior to any filtering) in the ultrasonic band but very close to the audio band. (These reflected signals can be called "noise", since they're not musically related to the desired part of the signal. Although the noise is correlated to the signal.)
"Well, I wonder if it is possible to design a filter that can get rid of those noise artifacts without damaging the wave shape and/or introducing gross phase shifts or is this something that is technically impossible within the boundaries of Red Book?"
That, my friend, is the confounding issue. Since half the sample rate (aka "Nyquist frequency") is 22,050 Hz, there is very little room to execute an effective filter to preserve bandwidth to 20,000 Hz. And the best filters in my opinion don't necessarily block everything at 22,050 Hz and above most-effectively, but preserve/reconstruct most of the waveform fidelity of what the signal was prior to digitization.
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Follow Ups
- RE: Tube DAC's ROCK - Todd Krieger 11:32:18 02/16/09 (0)
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