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Old 29th September 2003, 02:58 PM   #1
liz is offline liz  United Kingdom
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Question PCM to DSD conversion

Hi everyone

I need a means of converting a standard SPDIF output from PCM (probably just 24bit I2S to start with) into left and right DSD data streams with the appropriate clocks.

I've tried using a signal converter from dCS but this proved unsuitable for the application so I'm thinking of developing an FPGA-based solution.

Just wondering if anyone has developed or even just used a PCM to DSD converter? Any recommendations?


Thanks

Liz
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Old 30th September 2003, 05:12 PM   #2
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Default Re: PCM to DSD conversion

Just wondering if anyone has developed or even just used a PCM to DSD converter? Any recommendations?


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I have used the dCS972 and the 3 wire sdif2 interface works well. Can you convert this into what you want; there is adequte info on sdif2.
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Old 1st October 2003, 09:13 AM   #3
liz is offline liz  United Kingdom
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Thanks for the reply fmac.

I'm trying to ***** the performance of a DSD device using a signal source that originates as PCM data, so the conversion process needs to produce a very stable output and so far I've found the dCS972 SDIF2 IF to be too jittery for this application.
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Old 1st October 2003, 02:29 PM   #4
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I'm trying to ***** the performance of a DSD device using a signal source that originates as PCM data, so the conversion process needs to produce a very stable output and so far I've found the dCS972 SDIF2 IF to be too jittery for this application. [/B][/QUOTE]
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Can you not relock? I'd like to know what level of jitter you have found as I don't particularly like the sound of upsampled DSD on the 972/954. However, the 954 is supposed to have dual pll and you may be able to get the recovered data streams from there. I have found the cable connections to be very important.

Is the new firewire type interface any better?
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Old 1st October 2003, 02:46 PM   #5
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Since DSD is basically a SD-signal at 2.8.... Ms/s some 64x oversampling DA converter might probably be "misused" for this purpose.

Regards

Charles
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Old 1st October 2003, 05:12 PM   #6
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[QUOTE]Originally posted by phase_accurate
[B]Since DSD is basically a SD-signal at 2.8.... Ms/s some 64x oversampling DA converter might probably be "misused" for this purpose.

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Can you plrease explain how this relates to Liz@s and my posts?
Thanks.
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Old 2nd October 2003, 08:53 AM   #7
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Quote:
Originally posted by liz
Thanks for the reply fmac.

I'm trying to ***** the performance of a DSD device using a signal source that originates as PCM data, so the conversion process needs to produce a very stable output and so far I've found the dCS972 SDIF2 IF to be too jittery for this application.
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I looked up the 972 manual and the DSD data stream looks good. I have also examined the clock out on a scope and it seems to be one of the best I have seen; very square, well damped and no broadening.

One aspect about the dCs connection I have doubt about is the twisted pair connections inside the unit which is far from tidy. May be worth running true 75R outputs from, the pcbs.
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