[eweitzman]

You're correct in what you're saying, but there's more.

Just think about mp3 playback for a minute. Two channels of stereo are encoded into 32 or so low bitrate, frequency-limited channels. Possibly with joint stereo processing that collapses some channel pairs into single channels. Or flac for that matter: two channels of PCM are encoded as polynomial coefficients and correction bits. How do you play these through your DAC1? Your media player (foobar, winamp, whatever) converts these mishmashes into two channel PCM which the DAC1 then converts to analog.

Now take a six channel format. Different encoding, more channels in the end, but the same deal in theory. Hardware support is another matter, but I don't see any reason why a multichannel pro audio interface couldn't spit out six discrete (digital) PCM channels after the DTS/DD data has been decoded, leaving the D-to-A conversion to something else, like a triplet of DAC1s.

Maybe this isn't done for commercial or licensing reasons. Can somebody who knows chime in?

- Eric

 

[infinitesymphony]

Quote:

Originally Posted by eweitzman /img/forum/go_quote.gif Maybe this isn't done for commercial or licensing reasons. Can somebody who knows chime in?

I don't know for sure, but my guess is that there isn't a market for it. The best solution would be a multi-channel DAC, but those are practically non-existent. The only current multi-channel solutions are home theater preamplifiers and receivers.

If Benchmark released a multi-channel / home theater preamp version of the DAC1 PRE, I'd be there. Add IR remote on/off and volume support and I'd be there.

 

[furball]

PCM digital signal only carries 2 channels.


DTS/Dolby Digital signals are encrypted. The encryption is there for copyright protection. Because of the encryption, the DTS/Dolby Digital decoder is both a decoder and a multichannel DAC, you cannot separate out the two. The multichannel digital to analog conversion is done at the decoder level, and the decoder only outputs analog outputs. The decoder will not output PCM style digital output for each of the 5 or 7 channels.

I am sure there are ways around this. But you have to dig around on google to see what you can turn up.


If you want better sound quality for DTS/Dolby digital materials, get a USB DAC card that has an optical or coaxial digital output, hook it up to your receiver, let your receiver decode the DTS/Dolby Digital signals.

 

[EliasGwinn]

Quote:

Originally Posted by eweitzman /img/forum/go_quote.gif Maybe this isn't done for commercial or licensing reasons.

I believe this is true. However, ...:

Oppo DV-980H w/3x S/PDIF digital outputs pre-installed

 

[furball]

There are a mind boggling array of multi-channel compression formats, that's why you see new receivers come on the market so quickly. Receiver manufacturers cannot even keep up with the developments of these new formats. The receiver you purchased last Christmas is already obsolete by this time now.

I say Benchmark should leave all this multichannel stuff and the constant product cycling to the likes of Yamaha, Denon, Sony, etc., and just concentrate on doing an outstanding job with PCM decoding. Otherwise we will see a new Benchmark once every quarter, and the resale value of old Benchmarks would plummet...

Quote:

Originally Posted by infinitesymphony /img/forum/go_quote.gif If Benchmark released a multi-channel / home theater preamp version of the DAC1 PRE, I'd be there. Add IR remote on/off and volume support and I'd be there.

 

[infinitesymphony]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif I believe this is true. However, ...: Oppo DV-980H w/3x S/PDIF digital outputs pre-installed

Whoa... So, only $3,485 for the ultimate 5.1-channel DAC1 experience.

 

[furball]

Isn't stripping out and outputting un-encrypted digital signal from SACD's/DVD-A's kind of...illegal?

Anyways, I have a question, suppose you do have the 2 channel stereo PCM stream from SACD's/DVD-A's, can Benchmark DAC1 decode those signals?


Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif I believe this is true. However, ...: Oppo DV-980H w/3x S/PDIF digital outputs pre-installed

 

[EliasGwinn]

Quote:

Originally Posted by furball /img/forum/go_quote.gif Isn't stripping out and outputting un-encrypted digital signal from SACD's/DVD-A's kind of...illegal?

I don't know.

Quote:

Originally Posted by furball /img/forum/go_quote.gif Anyways, I have a question, suppose you do have the 2 channel stereo PCM stream from SACD's/DVD-A's, can Benchmark DAC1 decode those signals?

Yes.

Thanks,
Elias

 

[eweitzman]

furball,

PCM refers to how data is encoded/represented: as 16 bit (or 24 bit, etc) periodic samples. The S/PDIF and AES3 transmission standards carry two interleaved channels of PCM and some control info, but their two channel nature is not a limitation of PCM. ADAT carries 8 channels of PCM for example.

Within a playback machine, you might be able to get at the individual data channels after decoding from format XYZ to PCM. Looks like switch-box.com has done that. I read sometime ago that one of the Oppo machines was capable of outputting SACD digital data via the HDMI connection. As it turns out, the DSD data is converted to PCM (24/88 IIRC) and that's what you get. Not DSD, but not reconverted analog either. One of the later HDMI standards (1.3 IIRC) allows protected/DRM data to be passed through the interface with a protection flag.

The legal issues with SACD and DVD-A are different.

Because they are both encrypted digital data on discs, it is illegal to rip the data from the media in the US. But once the data has been converted to PCM signals inside a properly-licensed and manufactured machine, the data can be transported outside to other devices such as our DAC1s. There's a further issue with SACD in that the technology is licensed from Sony who stipulate (via licensing) that the digital DSD data stream NOT be made available outside the box. DVD-A might have similar licensing issues, I don't know about that. I'm pretty sure you can backup or play the decoded "LPCM" hi-rez streams from "enhanced" DVD-V like DualDisc, DAD, and so on. Copying is still verboten because it's copyrighted material, but not because of the encryption sanctions in the DMCA act.

In the case of the Oppo, they must be using one of the DAC chips that accepts DSD data, converts it to PCM, and then converts the PCM to analog. These DAC chips are the basis of the cheap universal players. I think these chips also function as sample rate converters so the PCM version of the DSD data can be grabbed as an output from the DAC chip. That's probably how SACD gets to go down the HDMI pipe in the vanilla Oppo, and also probably what the modifier grabs and sends to the three S/PDIF outputs that he adds to the back of the case.

I was thinking that something like the RME Fireface 400 could output the six PCM channels that could be derived from DTS/DD. It has an ADAT optical port that provides 8 channels of PCM. Again, it comes down to hardware: how would you connect three DAC1s to the ADAT output? Is there a breakout box of some kind that can sit in the middle?

- Eric

 

[eweitzman]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif I believe this is true. However, ...: Oppo DV-980H w/3x S/PDIF digital outputs pre-installed

That's too cool!

- Eric

 

[furball]

Very well written. And thank you for pointing out my misuse of some technical terms.

Well, like you said, it seems there is no hardware that can do what you want to do.

Would a software solution work? Of course then you have to make the software decoder output to 3 S/PDIF output channels. These have to be custom built.




Quote:

Originally Posted by eweitzman /img/forum/go_quote.gif furball, PCM refers to how data is encoded/represented: as 16 bit (or 24 bit, etc) periodic samples. The S/PDIF and AES3 transmission standards carry two interleaved channels of PCM and some control info, but their two channel nature is not a limitation of PCM. ADAT carries 8 channels of PCM for example. Within a playback machine, you might be able to get at the individual data channels after decoding from format XYZ to PCM. Looks like switch-box.com has done that. I read sometime ago that one of the Oppo machines was capable of outputting SACD digital data via the HDMI connection. As it turns out, the DSD data is converted to PCM (24/88 IIRC) and that's what you get. Not DSD, but not reconverted analog either. One of the later HDMI standards (1.3 IIRC) allows protected/DRM data to be passed through the interface with a protection flag. The legal issues with SACD and DVD-A are different. Because they are both encrypted digital data on discs, it is illegal to rip the data from the media in the US. But once the data has been converted to PCM signals inside a properly-licensed and manufactured machine, the data can be transported outside to other devices such as our DAC1s. There's a further issue with SACD in that the technology is licensed from Sony who stipulate (via licensing) that the digital DSD data stream NOT be made available outside the box. DVD-A might have similar licensing issues, I don't know about that. I'm pretty sure you can backup or play the decoded "LPCM" hi-rez streams from "enhanced" DVD-V like DualDisc, DAD, and so on. Copying is still verboten because it's copyrighted material, but not because of the encryption sanctions in the DMCA act. In the case of the Oppo, they must be using one of the DAC chips that accepts DSD data, converts it to PCM, and then converts the PCM to analog. These DAC chips are the basis of the cheap universal players. I think these chips also function as sample rate converters so the PCM version of the DSD data can be grabbed as an output from the DAC chip. That's probably how SACD gets to go down the HDMI pipe in the vanilla Oppo, and also probably what the modifier grabs and sends to the three S/PDIF outputs that he adds to the back of the case. I was thinking that something like the RME Fireface 400 could output the six PCM channels that could be derived from DTS/DD. It has an ADAT optical port that provides 8 channels of PCM. Again, it comes down to hardware: how would you connect three DAC1s to the ADAT output? Is there a breakout box of some kind that can sit in the middle? - Eric

 

[EliasGwinn]

Quote:

Originally Posted by eweitzman /img/forum/go_quote.gif how would you connect three DAC1s to the ADAT output? Is there a breakout box of some kind that can sit in the middle?

RME TDIF-1

I doubt that the Fireface will convert 5.1 encodes to multi-2-channel PCM's, but I could be wrong. Also, there may be some freeware out there that can do it. If anyone finds anything, let the rest of us know!!

Thanks,
Elias

 

[joijwall]

Does all this mean DAC1 understands PCM only, or does it know other digital to analog conversions also?
I'm also curious about the different players, both PC based and regular CD-players (at least the ones that plays MP3, I guess a CD is PCM?).
Are all players equally perfect when converting WAV, AIFF, AAC, FLAC etc into PCM? That is, will all send the same PCM-bits? Or do I need to choose player carefully?
/Joachim

 

[Tarkovsky]

Hi there joijwall, Elias was kind enough to provide us with a guide on the different players out there and how to get bit-perfect playback. You can find it over at the benchmark website but it's also linked to further back in this thread.

 

[gjwaudio]

Quote:

Originally Posted by infinitesymphony /img/forum/go_quote.gif Whoa... So, only $3,485 for the ultimate 5.1-channel DAC1 experience.

Well... maybe, but how are you going to change the volume ?

For ULTIMATE quality from such a 3xDAC1 setup, you can't use software to change the levels or you'll be tossing out bits (and some of your "resolution"). How can you implement the analog-domain output control, and have all six channels track together - without introducing another six-ganged volume pot between the DAC1 analog outs and your amplifiers ?

Can you imagine the grief using some Rube-Goldberg-esque arrangement to turn 3 DAC1 knobs in sync ? Sure... a custom Benchmark DAC-Racque to triangulate the controls just right, so the flywheel buffered MasterKnob (actuated by remote controlled step motor) adjusts each sprocket-modified DAC1 volume control via precisely tensioned, non-magnetic carbon fibre chain-link belts.

Laughable indeed... straight out of Charles Rodriguez... but just in case, I'm off to the Patent Office !

Cheers,
Grant