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Old 12th December 2012, 02:21 AM   #3371
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I have more partial good news. a friend gave me an AKM demo board (4103a) and that gives partial success with temporary i2s wiring. it does have a hw-mode that takes 128x rate, like the cirrus does. and for a few seconds, I was able to hear audio come out of the demo board while connected to the behringer. so, that chip has a chance of working, too.

maybe the i2s is just very weak and having 3 dac chips on the bus is strain enough and I'm pushing it over the limit. on both the cirrus and the akm, the sound dropped out a lot. I did use very very bad wiring, but I also abused the wiring on the audio widget and that thing is almost unsinkable it just always works, even with junky and long 'wrong' cables on the i2s lines. it does have a pretty strong and clean master clock and the behringer has a pretty weak looking one. the data lines are all private per dac chip but all the clock lines are shared.

some buffering might be worth looking into.
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Old 12th December 2012, 02:25 AM   #3372
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Quote:
Originally Posted by mhelin View Post
Have you checked the SDIN, SDOUT, CSB and GPO0 status flags, these should indicate any errors in hardware mode (which seems to be quite complex to set):
http://www.wolfsonmicro.com/document.../en/WM8805.pdf

Search "Table 17".
I have not looked at any status lines. in fact, I first had all lines tied up or gnded. then I thought gnding might be harsh for a line that could report status, even if I don't read it. so I pulled down with 1k's. I'm still not looking at the lines, though.

with spdif-in, I could see checking for errors. but I didn't think to check for error lights when you are taking in i2s and putting out spdif.

anyway, the more I look at the 8805 spec sheet, the more I think that hw-mode just can ONLY support 256x fs. and that is just NOT what is inside the dcx2496. leds or no leds, I don't think this dog is gonna hunt.
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Old 12th December 2012, 08:28 AM   #3373
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Actually there is a 24.576 MHz oscillator inside DCX2496. You might want to upgrade to Oettle's ASRC+clock module and use the 24.576 MHz clock supplied by it (might be good idea to use a proper shielded cable, if possible mount your S/PDIF transmitter closer the clock source):
Pilgham Audio - SRC/Clock

There is also another design (guess the best one, though ideally it would need an extra buffered BNC connector for your S/PDIF transmitter) here based to TI's ASRC (includes MSP430 micro) :
http://koti.mbnet.fi/jahonen/Audio/DIY/DCX2496DinSRC/

Third one which uses CS8416 SOIC part which is difficult to find these days.:
http://freerider.dyndns.org/anlage/B...ut-Stage-E.htm

Last edited by mhelin; 12th December 2012 at 08:39 AM.
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Old 12th December 2012, 10:59 AM   #3374
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8416 is an spdif receiver. how does that help getting spdif out of the box?
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Old 12th December 2012, 04:43 PM   #3375
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Quote:
Originally Posted by mhelin View Post
Actually there is a 24.576 MHz oscillator inside DCX2496.
do you have a handy tap location for this clock? I'm willing to try it.

update: I see clk12 and I guess that's the 12mhz clock that is there on master clock for the dacs. but I also see clk24! that must be what you are referring to? ic20b which is a 74hcu04 - that is doing some clock doubling already for me, it seems.

I'll see if I can find it and tap into it, IF that's the right one. thanks
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Last edited by linuxworks; 12th December 2012 at 04:56 PM.
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Old 12th December 2012, 07:56 PM   #3376
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SUCCESS!

yes, the 24.576 line is truly 24.576. just what the doctor ordered

photos of where the new tap location is for the master clock and also a level matching chip on my perf board (dip8 socket with 'flying soic' cmos schmitt trigger, running on 3.3v and outputing 3.3v but accepting the 5v level 24mhz clock input).

with all this in place, the wolfsons are now putting out spdif to my outboard dacs!

I am noticing some drop-outs every now and then, so the wiring probably still needs cleaning up. I might try skipping the ribbon and handling each line by itself via small coax (rg174 or equiv) runs.

but the basic idea IS now working!
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Last edited by linuxworks; 12th December 2012 at 08:17 PM. Reason: typos!
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Old 12th December 2012, 08:25 PM   #3377
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update: the wiring seems fine, I think. my home AC power line is glitchy and when I turn off my heating system, entirely, there are no more mutes happening every few minutes. one thing I did notice about the dcx2496, overall, is that its very sensitive to rfi and bad power. if I turn on a fluorescent light or a kitchen ceiling fixture light, the dcx chokes and chokes for several seconds before it recovers. always been that way, too, even before I got my hands on its insides

and so, when I work around my bad AC power (turning off the heating system, manually), the wiring or circuit can't be blamed anymore. I'm not hearing any muting or interruptions or bad samples or anything out of place when I listen to it.

for test, I've disabled the 24db/oct crossover slope I normally use and just run the channel in fullrange mode. then into a regular dac and regular amp and spkrs.

at some point, I'd like to capture the spdif-out using a digital sound card, then compare the files and see if anything gets dropped, over an hour or more. for right now, though, I'm listening to some quiet piano and if there are drop-outs or glitches, I'll hear it. and I'm not hearing any, with my AC power problems solved, at least.

I was about to shift over to the cirrus parts but it looks like I can use the board that I built afterall. yay!!
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Old 13th December 2012, 02:26 AM   #3378
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here's my system, together, with two DACs handling the HP/LP split.

notice that the two small DACs on the right have both of their status LEDs green. they are truly getting 24/96 audio from the output of the behringer!

from the 2 DACs, its as it was before, going into my cirrus 8ch vol control system and then out to a pair of stereo amps.

its playing now
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Old 13th December 2012, 04:16 AM   #3379
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photos of the working board (half wired).

being only half wired (one transmitter, only) makes the wiring a bit easier to follow, for those that may want to.

after I took this photo, I finished the board up and its now working with all 4 channels active.

the wiring was not really that bad. of course, a green board would be better...
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Old 13th December 2012, 08:53 AM   #3380
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That's incredible, congratulations!

And it looks like you're in for a PSU mod, too...

Cheers,
Sebastian.
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