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I2S or TDM for DAC or DSP

Posted by maxidcx 
I2S or TDM for DAC or DSP
April 11, 2012 10:44AM

Very impressive board. I will probably go with it soon.
I have some preliminary question on the product and then some questions related to my project:

1) does the features of the board (upscalling, dejittering, downmix 4.0) are also valid for a PCM signal coming from bluray or dvd ? or is it only or specifically for SACD DSD stream ?

regarding my project, I d like to link the vanity93 to a dsp board based on ADAU1445 (or like a MiniDSP board) in order to have cross over for triamping and some other types of correction before the amps.
Then the DSP would drive good DACs like AKM4396, but in PCM mode only.

1) is it possible or at least easily achievable to identify and pickup an I2S or TDM signal on the board, after the fifo dejitering, including MCLK, LRCLK and Data for the 6 chanels ? the idea is to create a small PCB including a line driver like LV244 and then put the signals on an HDMI femelle connector screwed on the Oppo rear panel to link with the external DSP board.

2) I anticipate that it is not imediately possible ! then I have the option to put SPDIF receiver on my DSP board, say 3 WM8805 or so. In such configuration, can you advise on the conection for the MCLK/SPDIF to the DSP and to the DACs, to minimize the impact of jitter produced by the WM receiver and the DSP themselves...? Shall we consider the DSP and the DAC as Slave of the Vanity MCLK/SPDIF ? or shall we use intenal ASRC for the DSP and sync the DAC on the Vanity MCLK/SPDIF clock ?

Thank you and great luck for success
Re: I2S or TDM for DAC or DSP
April 16, 2012 04:31PM
Thanks for your post. The signal processing features are related exclusively to DSD playback (DSD->PCM conversion). PCM signals are just passed through. The re-clocking function is then applied on all digital outputs regardless of their content. Please have a look into the settings manual for details.

Unfortunately I2S or TDM is not accessible on the board. S/PDIF signals are encoded directly form FIFO buffer. On the receiver side I'd suggest to use three or four SPDIF receivers (WM8804/5 are indeed great) and clock DSP and DAC synchronously without ASRC. Clock lines require careful routing, proper termination and buffering at critical points.

Universal players are not easily possible to slave due to number of various sampling frequencies usually derived from the video clock. Also there would need to be a dedicated data line with the information of the current sampling frequency from a DAC to the player.

Should you need more information, don't hesitate to ask.

Best Regards,
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