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Hi,
After numerous trials The DAC keeps unlocking constantly for S/PDIF and I2S. I tried the following:
1. USB/I2S converter switched off: No result for SPDIF.
2. Connected 4*SPDIF directly to Din with new ribbon cable: much less unlocks, but still not listenable. INA(Toslink1) gives better result then INB(Toslink2)
3. Changed DPLL settings: no result for SPDIF and I2S
4. Collected all power GND on a star GND connected to chassis: no result
5. Connected USB/I2S converter directly to Din: A few unlocks when switching TL lights on or off, but good music for hours without unlock.
This indicates to me nothing is wrong with the DAC or whatever circuit. It seems to me the sidecar is the bottleneck in all this, but honestly said: I really
don't know it anymore. I pulled all the tricks I know but as earlier said: I'm an analog man and this is my first digital project. It's clear to me now analog is totally different.
Please try to guide me in the right direction,
Kind regards,
Henri
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Update: 1. Made a direct connection between Toslink module and Din. So, no pulse transformers in between. S/PDIF is ok then. Hours music without one unlock. 2. Tested 4*S/PDIF and Sidecar, separatly and connected to eachother, with a 2MHz block wave (Max. range of my function generator). All ok. One question: Sidecar switches between S/PDIF an PCM. Should unused signals not be shorted to earth? F.I.: If you choose PCM, relays should short S/PDIF signals to GND and if you choose S/PDIF, relays short PCM signals to GND. I believe it would keep unused signals from interfering with others, also present at a very short distances on the relays contacts. Realising this is relatively easy to do, but sidecar has to be redesigned a bit  Conclusion: All circuits are fully functionable. Is there something I'm overlooking? Thanks for reactions Henri
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You would not want to short them to GND, because not all sources would handle a short to GND well at all. :)
Not all sources can be transformer coupled. You may simply want to omit the input transformer especially for TTL level sources.
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Hi Russ, Thanks for the reaction. Indeed not all sources tolerate shorting. Though in HF this is a commonly used practice. I'm reading some articles about proper grounding an I plan to rearrange the complete wiring of the DAC. http://www.rane.com/note151.htmlhttp://www.jensen-transf...an/generic%20seminar.pdfI've also drawn a scheme for proper grounding my DAC. See attachment. Can someone tell me if this a correct way to get rid of groundloops and assuring there is only ONE simple return path to ground? I think this will render a cleaner and more stabile signal. I'm not an expert in this matter thus all help is very welcome, kind regards, Henri Edited by user Friday, April 13, 2012 2:17:54 PM(UTC)
| Reason: Not specified henri47 attached the following image(s):  dacinterconnect.png (149kb) downloaded 298 time(s).You cannot view/download attachments. Try to login or register.
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YOu do very definitely want to use the GNDs on the ribbon cable as they help isolate the channels from each other.
For Toslink (TTL) either convert it to consumer level - or remove the input transformers on the SPDIF 4.
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Hi Russ, The only thing I don't wish to connect is the VD connection between Dac and Sidecar because I will power the sidecar trough the terminals on the side. Perhaps the scheme is a bit misleading, but alll the cable connections stay in place except VD. As for the SPDIF signals I first will try to take the signal off the toslink module directly without TTL levelshifting and see what happens. If connecting the TTL level signal directly to Din, the music plays with a few unlocks/hour; unlocks caused f.i. by switching on TL light etc. BUT: Connect the same signal to the sidecar and the mute light stays on. Looking at the SPDIF signal gives a perfectly stable signal without overshoot or ringing. Same story for I2S: direct connection to DAC: All ok; but: Via Sidecar: mute light stays on. Yesterday I took 4*SPDIF module and Sidecar apart and tested them thoroughly. All seems to be ok. It puzzles me why the DAC does'nt accept these signals. I attach 2 picures; One is a view of the inside enclosure and one is a close look at DAC-Sidecar-4*SPDIF assembly. Are the SPDIF lines too long? If so I rearrange the backpanel in the way that inputs are directly behind the 4*SPDIF module. BTW: What do you think about the new wiring scheme? Is it worth the trouble? Thanks for trying to help me on this Russ. It is highly appreciated. Kind regards, Henri henri47 attached the following image(s): insideBII.jpg (193kb) downloaded 255 time(s). P1050439.JPG (157kb) downloaded 263 time(s).You cannot view/download attachments. Try to login or register.
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I certainly don't see any harm in wiring it that way. My feeling is that if you replace the ribbon with some discrete wire and things start to work, it probably points to there being a faulty connection with the ribbon cable. Best of luck. I am happy to help. Edited by user Saturday, April 14, 2012 12:44:36 PM(UTC)
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I have marked up your drawing with some comments... Brian Donegan attached the following image(s): dacinterconnect.png (228kb) downloaded 248 time(s).You cannot view/download attachments. Try to login or register.
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Hi Russ ,Brian I checked the ribbons already many times and I'm almost 100% sure they are ok. But I'll follow your advice and try to solder the connections, just to be sure. @Brian: I attach a new scheme. Is it this you propose? Many thanks for your comments. kind regards, Henri henri47 attached the following image(s): dacinterconnect1.png (146kb) downloaded 220 time(s).You cannot view/download attachments. Try to login or register.
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Hello Brian, Did what you suggested ( but did not yet connect Safety earth to chassis) and guess what: SPDIF signals are much more stable now :d/ . Almost no unlocks. I2S has to be tested yet. I'll let you now what happens. btw.: Is it normal I measure around 300mV HF modulated noise on +5V of Placid HD. I do not think so. See attached picture. Could all the trouble I have may be linked to a problem of extreme noise ( oscillation?? ) on the power lines? kind regards, Henri henri47 attached the following image(s): P1050458.jpg (142kb) downloaded 172 time(s).You cannot view/download attachments. Try to login or register.
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Update: In the previous post I only used 1 Toslink module. The other was not connected (no power and no signal). After powering up the second Toslink module The first gave unstable Lock again!  The second Toslink module did the same. The first Toslink is connected to InA the second on InB on 4*SPDIF board. It seems they have a bad influence to each other  Back to square one? kind regards Henri
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What happens if you set SPDIF autodetect to OFF?
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LeonvB wrote:What happens if you set SPDIF autodetect to OFF? Then SPDIF input won't work at all. :)
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henri47 wrote:Update: In the previous post I only used 1 Toslink module. The other was not connected (no power and no signal). After powering up the second Toslink module The first gave unstable Lock again! The second Toslink module did the same. The first Toslink is connected to InA the second on InB on 4*SPDIF board. It seems they have a bad influence to each other Back to square one? kind regards Henri Henri have you omitted the signal transformers as I indicated for TTL SPDIF?
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Hello Leon, Just switched S2,5 to ON (Bypass) . It has no effect at all. kind regards, @ Brian: No, I did not, because when 1 SPDIF signal only is connected, all is normal. The DAC is not unlocking. Connecting the second Toslink makes both Toslinks unstable. I did conclude it's probably not a matter of using transformers or not. But I may be wrong of course. Edited by user Sunday, April 15, 2012 6:11:36 AM(UTC)
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Henri the Placid HD will sometimes oscillate if you have it set to source a lot of current and have little or no load, the reason is that the error amp runs out of current to adjust the shunt element. It also can happen if there is not enough headroom at the secondary. Check the rectified voltage at the Placid HD and ensure it is not sagging too much.
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Henri, even easier than omitting the transformers on the SPDIF 4 would be to put a voltage divider at the outputs of the TOSLINK modules to get the TTL voltage levels down. Something simple like 221-270R series and 47-75R to GND should suffice. No need to be very exact here. The comparator will be much happier with the lower levels. :) Edited by user Sunday, April 15, 2012 6:29:42 AM(UTC)
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I measure for Placid HD:
AC in: 10,3V
GND___TP Vin: 11,74V
VD: 5,16V
Tp out __ TP Shunt= 0,075V
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Hi Russ,
could possibly do it.
Is a schematic available for the Toslink module? If so it must be possible to shut down the level shifter and connect to the consumer SPDIF signal.
Thanks Russ
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Hi Russ Installed the voltage divider 270 sries , 75 toGND, but no effect. Voltage divider reduced SPDIF level to 0,5V (was 2,V) Update: unpowered second Toslink2 board and all is ok again????? Update 2: unpowered Toslink 1 and added power and signal to Toslink 2: More unlocks than with Toslink1 Edited by user Sunday, April 15, 2012 7:27:52 AM(UTC)
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