In Reply to: I thought this was "Mythbustered" already?? posted by Presto on April 16, 2007 at 15:45:19:
If you use a DAC with ASRC, you end up applying three filters to the audio:
1. ASRC resamples the data to try and reclock the data (to reduce incoming jitter)
2. the oversampling filter built into the DAC chip then apply oversampling on the resampled data
3. Finally, the analog reconstruction filter converts the output of the DAC (which is not entirely analog - typically it's a set of multi-level current pulses) into an analog signalSome would argue this is one filter too many, since there is no such thing as a "perfect" filter.
ASRC would make sense if there was a way of bypassing the DAC oversampling filter (unfortunately, not really possible with today's flagship DAC chips which use a "hybrid" architecture)
Non-oversampling would make sense only if the DAC chip was "perfect" (unfortunately, the NOS type designs tend to use the TDA1541 which is notoriously non-linear at low levels - not to mention it's only a 16-bit chip anyway)
And bypassing the analog reconstruction filter is usually not a good idea (results in too much ultrasonic artefacts).
For me, KISS is the best approach - just use a modern flagship DAC and live with it's oversampling filter (which is required to convert the signal to the hybrid format required by the DAC chip), feed it a signal that's as clean and unprocessed as possible, and use an analog stage that's as simple as possible that meets the DAC chip requirements.
Sounds simple, but in practice very few designs get there. Even a lot of pro audio cards like the Lynx and RME use a PLL generated clock which in my opinion is almost as bad as ASRC. And for consumer players, we have all sorts of issues which have been discussed here ad nauseam.
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Follow Ups
- I think the issue is that it's an extra set of filtering ... - Christine Tham 17:45:25 04/16/07 (26)
- Lynx and RME cards. - Presto 20:16:02 04/16/07 (25)
- Re: Lynx and RME cards. - laznos 20:35:39 04/17/07 (5)
- Correct - Christine Tham 20:45:12 04/17/07 (4)
- Re: Correct - RogerGraham 19:26:07 05/08/07 (0)
- Re: Correct - laznos 21:45:51 04/17/07 (2)
- Re: Correct - Christine Tham 22:28:15 04/17/07 (1)
- "Slave-Able" CD Transport..... - Todd Krieger 01:45:20 04/21/07 (0)
- Re: Lynx and RME cards. - Christine Tham 21:11:03 04/16/07 (0)
- Re: Lynx and RME cards. - Dawnrazor 20:58:41 04/16/07 (17)
- Re: Lynx and RME cards. - Presto 22:40:32 04/16/07 (16)
- Re: Lynx and RME cards. - Dawnrazor 23:12:11 04/16/07 (15)
- Re: Lynx and RME cards. - Presto 13:35:34 04/17/07 (14)
- Thanks for the list - Christine Tham 17:17:47 04/17/07 (3)
- For multichannel / tri-amping? - Presto 18:29:41 04/17/07 (2)
- Re: For multichannel / tri-amping? - Vincent VRS 20:07:57 04/17/07 (0)
- Re: For multichannel / tri-amping? - Christine Tham 18:51:33 04/17/07 (0)
- Re: Lynx and RME cards. - Dawnrazor 13:59:22 04/17/07 (9)
- You're luckier than me. - Presto 16:17:44 04/17/07 (8)
- Re: You're luckier than me. - Dawnrazor 22:56:18 04/17/07 (7)
- I'm not smart... - Presto 10:14:20 04/18/07 (4)
- Remember - KISS is best - Christine Tham 14:52:29 04/18/07 (3)
- Re: Remember - KISS is best - endust4237 14:06:48 05/01/07 (0)
- just a bit more information on clocks to help you understand - Christine Tham 18:13:39 04/18/07 (1)
- Thanks Christine. You're a walking wiki. That's a keeper. :o) nt - Presto 13:46:55 04/19/07 (0)
- Re: You're luckier than me. - Christine Tham 23:25:59 04/17/07 (1)
- Oops - Dawnrazor 08:07:47 04/18/07 (0)