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Old 25th July 2009, 05:27 AM   #1
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Default ADAT receiver

I made ADAT receiver board, based on AL1402G to output 4 channel I2S.
It looks like working now.
board was made by ExpressPCB, costs $91 for 3 mini boards.

Next I have to modify my CUDA-FIR channel divider to handle ASIO in/out.

I'm using E-MU 1010 PCI + EMU expansion board to accept word sync clock.
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Old 25th July 2009, 05:34 AM   #2
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here is schematic.
major parts are below, very simple.

U1 DS1812-5 DS1812-5+CT-ND
U2 LP2950-5 LP2950ACZ-5.0NS-ND
U3 LP2950-5 LP2950ACZ-5.0NS-ND
U4 TORX177 TORX177PLFT-ND
U5 AL1402G AL1402G
U6 74HC04

most expensive one is of course AL1402G, it costs about $24/chip.
bought from http://www.profusionplc.com/

Also I bought http://www.zzounds.com/item--ARTSYNCGEN masterclock generator. I will test 44.1kHz sync-mode when I get cable (ordered to Amphenol)
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Old 25th July 2009, 05:50 AM   #3
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Photo for LRCK, and SDATA5/6.

Q: what is this board for?
A: to supply I2S x 4 signal, to my full digital 4 way amplifier.

Q: why ADAT, not LAN?
A: I tried some network-CPU, like Atmel NGW100, NetBurner, AVR32, and tired. I could not build reliable, fast enough, stable multichannel LAN DAC. and these hardwares are too much (too many ICs).

Q: limitation?
A: 44.1kHz / 16bit / 8channel. It's good enough for me, If you want more, ADAT can be multiplied.

Q: what are you using as player?
A: iTunes / WMP / my own - etc. The output goes through "Virtual Audio Cable" to my FIR channel divider, then output to device by portaudio interface. This route will be changed to E-MU patchMix, it will handle ASIO i/o.

Q: board? or gerber?
A: ExpressPCB will not make gerber file, board file can be sent by eMail on request. (as is!)
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Old 25th July 2009, 07:24 AM   #4
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Hi Koon.

44.1/16 only! Hmmh. That's not very much.

Ever thought about building a PCI-E interface with separate powersupply?
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Old 25th July 2009, 09:56 AM   #5
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i see 3000 ps jitter too as limitation unless you use SRC or slave the source somehow to the endpoint .
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Old 25th July 2009, 04:51 PM   #6
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Hi,
Q: how to get 24/96?
A: use more expensive ADAT board, like RME.
2 ADAT channels can supply 24/96, 4way.

Q: dedicated board, separated power?
A: There is generic PCI IO board, http://www.hi-tronic.ca/?section=sho...&device=HT0601
and I have FIFO-to-I2S FPGA. (with separated power, only one clock here)
so it's possible but total building / price is not attractive than ADAT.
Power supply is separated on PC and on my ADAT receiver-Amplifier.

Q: Jitter?
A: Yes I purchased ARTGEN WORD SYNC clock generator, it's spec says < 100ps.
ADAT itself will be some thousands ps. if 1/30 improvement make sound quality, I can try more expensive clock generator.

TAS5518 re-sample signal and make it's own PCM data to convert PWM.
So I'm not expecting ARTGEN can make some change.
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Old 25th July 2009, 05:59 PM   #7
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especially for PWM, jitter is paramount. You need 20 ps for 16bit PCM equivalent perfomance.

You need total rejection of some form, nothing else would do IMHO.

1. ASRC for realtime
2. some sort of streaming (USB or Ethernet) into FIFO buffer with synchronous readout.

these are both known for total jitter rejection, TI has the 4 channel SRC4194 thats suitable for you. It has 28 bit math and 5th order lagrange interpolation preceded by 16x OS .

Heres a good document that 'd help :

http://www.tcelectronic.com/Media/fr...ocks_tc(1).pdf
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Old 25th July 2009, 06:45 PM   #8
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So, for TAS5518, itself has own clock and SRC,
"32-Bit Processing PWM Architecture With 40 Bits of Precision"
"8x Oversampling With 5th Order Noise Shaping at 32 48 kHz,"
for each channel to prepare PWM signal.

Of course I don't deny <20ps WORD SYNC generator, ASRC, FIFO for your own DAC etc.
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Old 25th July 2009, 07:07 PM   #9
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both Intersil and Zetex include an ASRC before their PWM modulator, I doubt you can get clean jitter spectrum like that without sacrificing something , eg. latency using a FIFO buffer.
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Old 25th July 2009, 07:27 PM   #10
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the TAS5518 definately has no ASRC.
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