Hi mhelin - do you please have contact on guy make this? - or some more info - i like it very much
thanks
Tomas
I suspect its some LDO stuff inside. some other products that make use of LDOs also seem to drop-out at the slightest change in power or static. my emu 0404usb sound device is like that, even when I avoid its switching wallwart and give it a linear supply, if there is any electrical faults or even a soldering iron pulsing on and off, that will cause drop-outs on the EMU. it uses a lot of LDOs inside.
I don't really understand why this happens, but a few boxes I have (some diy, some commercial) are very sensitive like this.
after replacing the whole psu module on the behringer (a plan for later) I'll know for sure.
its not about the case, since its a decent enough metal case and it gets grounded via the 3 prong IEC.
I don't really understand why this happens, but a few boxes I have (some diy, some commercial) are very sensitive like this.
after replacing the whole psu module on the behringer (a plan for later) I'll know for sure.
its not about the case, since its a decent enough metal case and it gets grounded via the 3 prong IEC.
The I/O signals between the existing SRC CS8420 and the DCX DSP board are all 5V type. The I/O signals of the jahonen mod all seem to be 3.3V type. Might be this works somehow but it’s an incompatibility which can cause problems.
Good point, though I guess there are reasons why 3V3 is used. Maybe it has been made it possible to regulate the power lines a little bit better. The schematics don't show it but BOM does, there is a LDO type TPS70851 3.3V/1.8V regulator on board. The ADSP-21065L anyway is a 3.3V device so it doesn't matter in fact.
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!
Excellent you got it working (and thanks for the beer even though it's about 5300 miles from here, maybe you can send be the PCB for the S/PDIF transmitter board instead if you end up making one). There are so many mods you need to do for this Behringer to get proper results, modding the PSU might be a good one. Designing better PCB for the transmitter with SMA PCB connectors for coaxial cables might be good idea, maybe it would be worth adding the third transmitter as well for channels 5/6. One thing I've been wondering is the use of the 12MHz oscillators, are they really needed? Have you tried using the transmitter without them? The data sheet doesn't tell how the chip should be configured if you use only the transmitter but not the receiver at all.
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Regarding the coaxial connectors, could these be soldered on the DCX2496 PCB (to the resistors and vias, maybe using epoxy or some plate with holes drilled for connectors to make it physically stronger):
1-1478966-0 - TE CONNECTIVITY / GREENPAR - SOCKET, SMA, BULKHEAD | Farnell Suomi
and these put on the S/PDIF transmitter PCB:
5-1814400-1 - TE CONNECTIVITY / AMP - SOCKET, SMA, RIGHT ANGLE, 50OHM | Farnell Suomi
Also how about adding the Word Clock send? Guess that would reduce jitter if the receiver DAC has the WC input.
1-1478966-0 - TE CONNECTIVITY / GREENPAR - SOCKET, SMA, BULKHEAD | Farnell Suomi
and these put on the S/PDIF transmitter PCB:
5-1814400-1 - TE CONNECTIVITY / AMP - SOCKET, SMA, RIGHT ANGLE, 50OHM | Farnell Suomi
Also how about adding the Word Clock send? Guess that would reduce jitter if the receiver DAC has the WC input.
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I plan to find out if those stupid tin cans ARE needed 
its not clear. I've been thru the data sheet many times and its still not obvious if they are needed for all functions. I guess I'll remove them and it will be easy to see first-hand.
I like the idea of small coax connectors on the board. the little ones you find for GPS antennas (many kinds) would be perfect. they have all the specs we would need, and beyond. that covers the new pcb but it does not solve the tap-points problem.
one idea could be to have a small board sit right on the behringer and provide a break-out, like my hot melt glue idea, but better and more proper. small wires that go from the behringer to the breakout, then you could have the SMA coax connectors go from there. ideally, it would be great to just buy pre-made thin rf coax cables and just use them.
for the real pc, yes, I would do 3 chips. no reason not to. on my perf, I didn't need to do 3x the work (lol) and space was tight as it was. on a green board, though, I'd absolutely include all 3 pairs of channels.
I do tend to like wolfson chips, but the cirrus does not NEED (or want) any xtal boxes. and for diy, the cirrus parts are easier to solder, too.
its not clear. I've been thru the data sheet many times and its still not obvious if they are needed for all functions. I guess I'll remove them and it will be easy to see first-hand.
I like the idea of small coax connectors on the board. the little ones you find for GPS antennas (many kinds) would be perfect. they have all the specs we would need, and beyond. that covers the new pcb but it does not solve the tap-points problem.
one idea could be to have a small board sit right on the behringer and provide a break-out, like my hot melt glue idea, but better and more proper. small wires that go from the behringer to the breakout, then you could have the SMA coax connectors go from there. ideally, it would be great to just buy pre-made thin rf coax cables and just use them.
for the real pc, yes, I would do 3 chips. no reason not to. on my perf, I didn't need to do 3x the work (lol) and space was tight as it was. on a green board, though, I'd absolutely include all 3 pairs of channels.
I do tend to like wolfson chips, but the cirrus does not NEED (or want) any xtal boxes. and for diy, the cirrus parts are easier to solder, too.
The used 3.3V devices all need a 3.3V supply. So the 3.3V supply is correct. The problem is that the used devices are all 3.3V devices which need and generate 3.3V I/O signals which is incompatible with 5V devices on the DCX DSP board. For correct operation a 3.3 to 5V converter for all I/O signals would be needed.
No devices in digital audio signal path are 5V devices, all are 3.3V. The DSP and the converters all use 3.3V supplies, only the analog parts of the A/D and D/A converters use 5V (for better SNR). See Behringer Diagrams, Schematics and Service Manuals for FREE
E: Is it possible older revisions of DCX2496 were using 5V supplies? Got to check mine some day.
E(2): Seems the 5V supplied 8420 on DCX outputs SDOUT via a voltage divider (220ohm/+330ohms), other signals directly to 3.3V chips.
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I wished you were right. There is only one version of DCX and there all relevant devices (IC 1, 19 (VIO), 20, ...) use 5V. Have a closer look at page 2 and 3.
Does anyone have any information on exactly what IC19 does? It's a Quick Logic QL3004 but I can't seem to find any data on it.
It looks like either a level translator or some sort of re-clocking or switch interface.
All digital I2S paths run into and out of this IC before making their way to the I2S inputs on the SHARC DSP.
The SHARC datasheet specifically mentions that it supports direct I2S connection to any I2S standard ADC or DAC, so has anyone tried bypassing the entire front and back end, sending input directly to and output directly from the SHARC DSP? This could allow bypassing all on-board clocks and digital circuitry with the exception of the 30MHz clock for the DSP itself.
I might try it with my Amanero USB-I2S board this evening on the input side... that would allow a nice USB connection directly on the back of the DCX-2496 for digital input, which runs directly into the SHARC. No need for on-board ASRC, clocks, etc...
Cheers,
Owen
When you want multichannel for home theatre where source may not always be the computer. Small computer with ability to switch between analogue input and software sources as well as 8 to 12 analogue outputs is well down the price per performance scale in my opinion. Why 12? 3 way left/centre/right speakers, LFE channel, rear speakers ...
Even 6 channel of dacs and a good stereo adc for a 2 speaker stereo system is a significant investment for a system that might be used for a prototype and untested speaker system.
Basically if I was to do a computer setup I'd be either using a really cheap mulitchannel adc/dac at least through the prototype phase, even fully built it is a cumbersome environment and has a learning curve associated with it that if installed in a living space with significant other and family members using the same space it has constraints that they may not be willing to live with.
Meanwhile the guy using a DSP platform has things working Good Enough TM
I guess you havent been following the conversation, by this point after Owen's mod (and to a degree linuxworks) above, the DSP is the only thing left running in the case, no dacs, no ADCs, no clocks, no analogue outputs.
thus my comment.
also pretty sure both of them already have ADCs, DACs and Amps covered
thus my comment.
also pretty sure both of them already have ADCs, DACs and Amps covered
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I considered that... starting from scratch with just the SHARC DSP and an ESS DAC and ADC would be ideal, but the value of the finished chassis and polished user interface of the Behringer would be tough to beat.
I really love the fact that the Behringer is self contained, and isn't tethered to a PC. You can swap between a digital source or analog inputs, and the UI is really top notch once you know how to use it.
The only problem is that it sounds like absolute rubbish, and I don't say that lightly. Most of Behringer's stuff does fall into the "good enough" category, but unfortunately the DCX2496 does not. There is obscene levels of noise when using the AES/EBU digital input, and there's something about the sound that really grates on my nerves. It seems to measure acceptably well, but it certainly doesn't sound that way.
I've got a project going where I actually need mine to work properly and sound good, so I'm finally looking into what I can do about it.
Step 1 will be the PSU, then step 2 is the digital input (to alleviate the AES/EBU noise issue). Step 3 will either be a digital output scheme, or an internal ESS9018 DAC in multi-channel mode.
Before I go down that path though, I want to know if IC19 is doing something horrible to the clocks. If it is, then it will have to be bypassed, but the solder points on the SHARC DSP are not very pleasant to try and tie into
Cheers,
Owen