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dpaws  
#1 Posted : Friday, April 20, 2012 9:55:10 AM(UTC)
dpaws

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Hi Guys

I'm about to embark on a project which will leave me seriously out of my depth! The device is a digital music server which in standard form outputs only analogue stereo. However, I would like to extract a digital signal via SPDIF.

I don't have the full schematic, but the block diagram is here:

UserPostedImage https://skydrive.live.co...p;resid=A332BC3AEFC89F6B!648&parid=A332BC3AEFC89F6B!248&Bpub=SDX.SkyDrive&Bsrc=Share

https://public.blu.livef...Block_diagram.JPG?psid=1

I need to retain all of the original system functionality, "simply" hijack the digital signal as it passes through the device.

I assume I could utilise the Transceiver board but I have a potential problem. The digital source requires two system clocks (x44.1kHz and x48kHz) so I would need to upgrade the two clocks inside the unit at present and then slave the daughter board to them (I don't want to use the Metronome). The highest resolution handled by the player is 24/96 and that's sufficient for my needs.

Where on earth do I start? Is it apparent from the diagram where the ideal intercept point is? BTW I don't need the digital volume control in the circuit but if it's there that's fine as it'll be left on 100% or disabled by the software interface if that's possible.

Very much obliged...

Edited by user Friday, April 20, 2012 10:08:35 AM(UTC)  | Reason: Not specified

dpaws  
#2 Posted : Friday, April 20, 2012 10:06:18 AM(UTC)
dpaws

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Argh!!! Sorry guys, my HTML is lacking for some reason - I guess copy/paste the whole link :( or just mail me dpaws at hotmail dot com and I'll happily send a copy

Edited by user Friday, April 20, 2012 10:06:53 AM(UTC)  | Reason: Not specified

LeonvB  
#3 Posted : Friday, April 20, 2012 10:55:50 AM(UTC)
LeonvB

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I don't see the problem: the output towards the DAC is I2S. Look for the DAC chip, read the datasheet and identify the correct pins. Put a Teleporter in the device and you're done, and it's even better than S/PDIF.
dpaws  
#4 Posted : Friday, April 20, 2012 11:28:57 AM(UTC)
dpaws

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Thanks for the thought - I agree, it would be a neat interface. However, the next item in the audio chain is a NAD M2 digital amplifier for which I have no schematic or block diagram... Would you be confident in finding the right place to attach the other teleporter inside the NAD?

Also, please note that the "DAC" noted on the schematic is not the main DAC but is only to drive the internal effects speaker for the UI

Edited by user Friday, April 20, 2012 11:44:06 AM(UTC)  | Reason: Not specified

LeonvB  
#5 Posted : Friday, April 20, 2012 1:16:55 PM(UTC)
LeonvB

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If the DAC in the drawing isn't the DAC, you have to look at the microprocessor: it has an I2S interface to the FPGA chip. It likely uses this FPGA chip to do the D/A conversion.
Regarding the M2: that uses a Xilinx FPGA chip, so it is likely a similar construction can be found there. And even if you can't find it: you can create an external solution to feed it S/PDIF from the media servers' I2S signal.
On the whole though, it does sound like a lot of work. I'm puzzled: why don't you replace the media streamer for one with S/PDIF output?
dpaws  
#6 Posted : Friday, April 20, 2012 2:29:46 PM(UTC)
dpaws

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Ahha I keep asking the same question - though aesthetically it is a beautiful solution
dpaws  
#7 Posted : Friday, April 20, 2012 3:36:18 PM(UTC)
dpaws

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May I take your email address? Incredibly I've just obtained an M2 service manual with schematic...
LeonvB  
#8 Posted : Friday, April 20, 2012 9:46:12 PM(UTC)
LeonvB

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dpaws wrote:
Ahha I keep asking the same question - though aesthetically it is a beautiful solution

I don't understand why you keep asking that. If the FPGA does the D/A conversion you'll have no other choice. You want to intercept the digital signal, and that's virtually the only point where it is exposed. You can PM me.
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