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In Reply to: "24-Bit 192k 8 Times Oversampled Upsampling." posted by Todd Krieger on April 16, 2007 at 03:49:00:
nt
Follow Ups:
With classic "8x oversampling" synchronous conversion (and also 24/96 upsampling via DSD), the output signal is coupled to the input signal via a common clock. If there is jitter at the input, the oversampled signal will have a variant of that jitter as well, but the amplitude of the signal is purely a function of the digital filter algorithm. No additional noise is added.The problem with ASRC is the input and output are run by *independent* clocks. Now at the outset, this may seem desirable, but what happens is the input signal is oversampled at an extremely high rate- The ASRC enables the output to simply grab the sample closest to the output clock trigger. But the problem arises from the input jitter, which is transferred the intermediate oversampled signal, being shifted in time relative to the output clock. The input jitter is de-correlated from the output clock, but shifting the waveform (the jitter error) makes the output see a different **amplitude** than what it would have seen without jitter. This results in the jitter being transformed to noise.
This noise is not only due to input jitter, but in actuality due to the combined jitter of the input signal and output clock. And from listening, I think this high-frequency "haze" riding on the music is the by-product of ASRC. For when I listen to standard conversion, this HF "haze" is conspicuous in its absence.
To me (but not necessarily to everyone), ASRC-based digital playback is *very* fatiguing to listen to. And a lot of the initial sonic bliss people have with these products is soon followed by yet another round of sonic frustration.
How about Rega, are their players ASRC?
nt.
My best answer to that is an episode I once had in Tucson, AZ. I was in a computer lab at Raytheon, doing some legacy testing. Suddenly, out of nowhere, a nearby computer monitor (all were CRTs at the time) started emitting a **loud** HF whistle from the flyback transformer. I just jumped up and bolted out of the lab. A technician in the lab, in seeing me do that, wondered what the problem was.....I haven't heard every unit out there, and there may exist ASRC units that I may actually like. I think there's something wrong with the technology, but I'll never question anybody who likes how such products sound. No two people like the exact same things.
a better reply. Thanks anyway.
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