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108.3.18.39
In Reply to: RE: New Developments in USB DSD DAC's and ADC's posted by alexcount on December 20, 2010 at 17:02:17
HowdyIt's not my glass interface :)
The EMM Labs equipment (both pro and consumer) use AT&T ST glass fiber e.g. http://www.frys.com/search?query_string=4706599)
They use transceivers of the type pictured: Avago HFBR-2416TZ (http://www.avagotech.com/pages/en/fiber_optics/general_purpose_industrial_control_data_link_820nm/hfbr-2416tz/) Some relevant app notes are: Application Note 1121, Application Bulletin 78 and Application Note 1123.
In general Meitner uses three links between the transport and the DAC, clock out from DAC to Xport, clock into DAC from Xport and data into DAC from Xport. The clock from the DAC to the transport is optional in which case the transport shoves data down the DACs throat :)
The data is simply bytes of samples @ 64Fs (or 128Fs), each bit for a different channel. The clock runs slower and they obviously use a PLL to multiply it up. There are other details but since all I know is by using my scope and FPGA, any more would be speculation :)
I chose to put two HFBR-2416TZ interface modules on my board simply because I have a EMM Labs CDSD transport and it's simpler hooking up a fiber cable (or two) than hooking five clips onto chips in a S9000ES...
The problem is that Sony doesn't like raw DSD bits running around so I wouln't count on anyone supporting this interface.
I'll write ASIO drives first if I write my own USB drivers, but there are now some turnkey USB chip/driver solutions which don't involve licencing issues and support the expected USB modes as well as async.
-Ted
P.S. For more details about my board if you are curious: http://www.audioasylum.com/forums/pcaudio/messages/8/80732.html I am having fun with it.
Edits: 12/20/10Follow Ups:
"The problem is that Sony doesn't like raw DSD bits running around so I wouln't count on anyone supporting this interface."
Why do you think that Sony could stop people from sending raw DSD bits around? How might they do it?
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Howdy
I never said that you couldn't send bits around: in fact I've told people that I do it. Sony doesn't care about random DSD bits, they only care about bits which are copyrighted flying around loose :) The SACD pit width code and encryption seems to work well and is well designed.
I just said that I double that the interface as implemented will ever fly for a company. There are two obvious issues if you market an interface:
.) In my mind the moral issue of facilitating others to break the copyright laws. (I only rip SACDs I own and I don't share bits.)
.) If you send the bits (sourced from SACDs) around unencrypted you'll never be able to market your device as a SACD device and I believe it's also a violation of the DMCA.
-Ted
All bits are born copyrighted. You have to buy a first license from Mr. One and a second license from Mr. Zero. :-) In Fascists states, breaking DRM on material that you own so you can enjoy "fair use" is a crime, but then there are many other innocent activities that are crimes in Fascist states.
There are patents on the method of storing the encryption key ("pit processing") on SACD disks, but these certainly don't apply here. There are other patents on editing DSD, none of which really work anyhow. There are patents on DSD compression and on DSD modulators. The basic format (pulse density) has been used for a long time—I was using it in some code I wrote for an Apple II in the late 1970's, but I won't say what the code used for. :-)
I don't mess with SACDs because of the DRM. It was one of several reasons why SACD failed in the marketplace.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
HowdyOr one of the reasons it's done as well as it has...
(Not that I like the RIAA)
-Ted
P.S. That's the beauty of good encryption: you can know everything about it and still not break it (or at least have a devil of a time.)
Edits: 12/23/10
The Playback Designs MPD-3 will be out at CES and will be able to accept DSD and DXD over USB.
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