André Gosselin

Native DSD versus DOP comparison

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I am almost sure this has already been discussed somewhere on CA, but can't happen to find it.

Could someone point me to a thread where the advantages/disadvantages of DOP vs native DSD are discussed ?

 

Thanks for you help

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This topic could lead to quite a heated debate around these parts! DoP simply uses PCM frames as a carrier for the native DSD data, so once successfully received and unpacked the resulting DSD data should be bit for bit identical to the original native DSD data. Any difference heard in playback quality between native DSD and DoP would then be due to the additional processing load required by DoP to unpack the data which can cause some undesirable side effects which could induce additional noise or jitter. That's my two cents on the topic, but please keep in mind the expression "you get what you pay for".

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I am almost sure this has already been discussed somewhere on CA, but can't happen to find it.

Could someone point me to a thread where the advantages/disadvantages of DOP vs native DSD are discussed ?

 

Thanks for you help

 

As far as I am concerned the only "disadvantage" for DoP is that it requires high rate PCM capability for those who want to be able to playback high rate DSD files: DSD 64 requires a 176.4 PCM package, DSD 128 requires a 352.8 PCM package, and DSD 256 requires a 705.6 PCM package. Not a lot of DACs can do 705.6 PCM, so DSD 256 delivery is generally limited to Native DSD streams.

Other than the above limitation, there is NO downside to DoP, as the "extra processing" required is negligible. "Packing" DoP is not like oversampling and filtering, which does require significant processing. I checked this on my Mac: using Jriver to send DoP DSD 128 required no more CPU activity than playing back native 24/96 PCM files.

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As far as I am concerned the only "disadvantage" for DoP is that it requires high rate PCM capability for those who want to be able to playback high rate DSD files: DSD 64 requires a 176.4 PCM package, DSD 128 requires a 352.8 PCM package, and DSD 256 requires a 705.6 PCM package. Not a lot of DACs can do 705.6 PCM, so DSD 256 delivery is generally limited to Native DSD streams.

Thanks for those important infos. Is there a link explaining the "maths/physics" behind those numbers ? They remind me of the advice that transcoding a DSD64 to PCM is best done at a 176.4 frequency, DSD128 at twice that frequency, etc. (advice coming from minimserver author who has implemented such a trancoding possibility in his excellent software).

 

Other than the above limitation, there is NO downside to DoP, as the "extra processing" required is negligible. "Packing" DoP is not like oversampling and filtering, which does require significant processing. I checked this on my Mac: using Jriver to send DoP DSD 128 required no more CPU activity than playing back native 24/96 PCM files.

Isn't there a small (or not so small) overhead inside the DAC (as opposed to the external music server) to recover the DSD signal from its DOP "camouflage" and which could impact SQ ?

 

Thanks

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Thanks for those important infos. Is there a link explaining the "maths/physics" behind those numbers ? They remind me of the advice that transcoding a DSD64 to PCM is best done at a 176.4 frequency, DSD128 at twice that frequency, etc. (advice coming from minimserver author who has implemented such a trancoding possibility in his excellent software).

 

 

Isn't there a small (or not so small) overhead inside the DAC (as opposed to the external music server) to recover the DSD signal from its DOP "camouflage" and which could impact SQ ?

 

Thanks

 

There is no reason to believe that unpacking (in the DAC) DoP would require anymore processing power than packing it (in the server) requires, and as I have mentioned, packing it requires virtually nothing in terms of processing power. There are no conversions involved or fancy maths (unlike digital filtering/oversampling), it is simple stuff.

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Is there a link explaining the "maths/physics" behind those numbers ? They remind me of the advice that transcoding a DSD64 to PCM is best done at a 176.4 frequency, DSD128 at twice that frequency, etc. (advice coming from minimserver author who has implemented such a trancoding possibility in his excellent software).

 

As for mathematics as for physics DoP or native DSD is no matter for sound quality. Like FLAC vs. WAV.

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Thanks for those important infos. Is there a link explaining the "maths/physics" behind those numbers ? They remind me of the advice that transcoding a DSD64 to PCM is best done at a 176.4 frequency, DSD128 at twice that frequency, etc. (advice coming from minimserver author who has implemented such a trancoding possibility in his excellent software).

 

 

Isn't there a small (or not so small) overhead inside the DAC (as opposed to the external music server) to recover the DSD signal from its DOP "camouflage" and which could impact SQ ?

 

Thanks

 

The math is very, very simple. A "word length" of 16 bits is used to pack the DSD bitstream for DoP. Multiply 352,800 by 16 and you get 5.6M, in other words DSD128. So that's why you need 352.8K PCM capability to transmit DSD128 over DoP, 705.6K to get DSD256, and so forth.

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"Packing" DoP is not like oversampling and filtering, which does require significant processing. I checked this on my Mac: using Jriver to send DoP DSD 128 required no more CPU activity than playing back native 24/96 PCM files.

 

What about the processing required to unpack at the USB receiving interface, which means processing near the DAC chip most of the time?

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As for mathematics as for physics DoP or native DSD is no matter for sound quality. Like FLAC vs. WAV.

 

Except when your computer is directly connected to the DAC (most of them are not totally isolated) by USB, the extra processing can cause noise affecting the D/A at the DAC.

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What about the processing required to unpack at the USB receiving interface, which means processing near the DAC chip most of the time?

 

Is the DoP marker/flag read at the USB receiver? If so you make a great point. Where is the marker read when DoP arrives via SPDIF, for example?

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Is the DoP marker/flag read at the USB receiver? If so you make a great point. Where is the marker read when DoP arrives via SPDIF, for example?

 

Doesn't DSD require SDIF rather than SPDIF?

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Doesn't DSD require SDIF rather than SPDIF?

 

My point was that there are many DACs that support DoP via digital inputs, for example SPDIF inputs (like Chord, etc). I wondered where the marker was read in that signal path.

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My point was that there are many DACs that support DoP via digital inputs, for example SPDIF inputs (like Chord, etc). I wondered where the marker was read in that signal path.

 

"Many" might be a little strong according to your/Jesus/Brian's invaluable DSD Database (https://docs.google.com/spreadsheets/d/1GPtrINDXXFW9Nm7A7YJ6Jsiu54hKXD7vUmrAbtwrSG0/edit?pref=2&pli=1#gid=0) :) , but it's a worthwhile and interesting question to which I don't know the answer.

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The one issue I have experienced with DoP was that I would get a rather loud & annoying pop when the last song of an album finished playing. Supposedly, it was my DAC (USB board to be more precise?) switching from DSD to PCM mode that caused the pop. Generally, this is some type of "mute" feature to avoid this from happening but apparently my DAC (USB board) did not have it.

 

In converting PCM to DSD, I always had this issue. In playing DSD material, I generally got a slight tick between tracks as well.

 

I updated my USB board (JLSounds) to a newer version with firmware that could handle native DSD (non-DoP) and that solved everything. No more pops, ticks, etc.

 

I had talked to Andreas Koch at RMAF a few years ago and he admitted that it really depends on how well DoP has been implemented by the developer.

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The one issue I have experienced with DoP was that I would get a rather loud & annoying pop when the last song of an album finished playing.

 

May be random values was at part of last DoP's frames because real audio stuff can't fill the last frames to end?

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My point was that there are many DACs that support DoP via digital inputs, for example SPDIF inputs (like Chord, etc). I wondered where the marker was read in that signal path.

 

Ted, there are only a small handful of DACs which allow DoP over SPDIF, like Chord. As these companies are also ones who typically do things their own way, I suspect that one would have to inquire directly with them.

 

In any case, the actual processing required to unpack DSD is virtuually nil, no matter where it is done. creating I2S for the DAC out of a USB stream, for example in a USB receiver) requires so much more activity (100s of times more) that it is absurd in the extreme to suggest that unpacking DoP will have any effect whatsoever. Additionally, this is just another reason why manufacturers should use isolated USB receivers (from the DAC chip), to qualm somewhat crazy audiophile fears.

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Sorry for the "many" but our database has 40, and I have experienced it on several (yes, I do mean several) dacs inhouse, including 4 Chords, 3 Myteks, an MSB and one or two others. DACs like Chord, Mytek and MSB are pretty popular around here. So, no, I was not being hyperbolic.

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Sorry for the "many" but our database has 40, and I have experienced it on several (yes, I do mean several) dacs inhouse, including 4 Chords, 3 Myteks, an MSB and one or two others. DACs like Chord, Mytek and MSB are pretty popular around here. So, no, I was not being hyperbolic.

 

Hey Ted, no worries, that is actually a lot more than I was aware of!

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Don't forget my $450 Gustard :D

I tried it with Gustard U10 USB to SPDIF / AES converter.

DoP worked both through AES and SPDIF.

 

13499d1404642713-direct-stream-digital-vs-everything-else-coax_dsd64.jpg

 

So the DoP processing has to be implemented in some common part, it doesn't seem to be input interface specific. I'm not HW developer, but many DACs use Altera FPGA, including my Gustard. Could it be here?

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