Grace Design m905 Reference Monitor Controller

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Caleb
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Joined: Thu Apr 04, 2013 10:14 pm

Grace Design m905 Reference Monitor Controller

Postby Caleb » Sat Feb 08, 2014 8:13 pm

Version: 1
Status: Complete
License: Custom Licence

http://www.gracedesign.com/products/m905/m905.htm
The XMOS L2 processor in this product provides receive and transmit of digital audio in various formats: USB, AES3 single and dual wire, S/PDIF, TOSLINK, ADAT (+ SMUX). USB may be synchronized to any of the inputs as well as Word Clock. USB interface permits playback of PCM sample rates up to 192kHz as well as DSD and dual-rate DSD. 
The program was largely derived from the elements of the L2 MultiChannel reference design. Some optimizations include: greatly improved jitter performance of S/PDIF, AES3 and ADAT clock recovery, elimination of USB explicit feedback, successful receive of 192kHz AES3 "black", DSD.
Clock jitter performance if further imporved by a secondary VCXO-based PLL, which is typical of Grace Design monitoring products. 
 
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Bianco
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Postby Bianco » Sun Feb 09, 2014 1:49 pm

Is this project to be open sourced?
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Caleb
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Joined: Thu Apr 04, 2013 10:14 pm

Postby Caleb » Mon Jun 30, 2014 6:54 pm

A great deal of the code is direct from the reference project. Not much else is relevant without the conext of the hardware, host microcontroller interface protocol and product feature set. There's a proprietary host microcontroller interface and control of custom secondary mclk PLL. And, there's a great deal of work done with implicit feedback to appease macintosh in the context of utilizing ADAT and SPDIF receivers independant of USB streaming from host. All that additional code - no we won't be publishing. There's a lot of it that I'd do completely different now that I've gotten through a couple of producd designs with XMOS USB audio and understand it quite a bit more. I'd be willing to discuss specific issues / solutions if there's something particular you iterested in. 
Along the way I helped Henk Muller fix a SPDIF Rx bug that failed to lock on 192kHz "AES Black" / muted AES data at 192kHz. This fix is found in that module on github; perhaps it made it into the current reference project - I'm not sure. 

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