Behringer DCX2496 digital X-over

[tomtom]

Originally Posted by mhelin

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) :
Index of /jahonen/Audio/DIY/DCX2496DinSRC

Hi mhelin - do you please have contact on guy make this? - or some more info - i like it very much

thanks

Tomas

[AndrewT]

Emi susceptibility.

Is there a way to make the DCX less susceptible?
Is it a mains input problem, or a radio signal problem?
Is it a case/chassis that is not screening well enough?

[linuxworks]

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.

[AndrewT]

LDOs operating with a smidgen of Vdiff?

[mhelin]

Originally Posted by tomtom

Hi mhelin - do you please have contact on guy make this? - or some more info - i like it very much

thanks

Tomas

Try this one (not sure though if the email link is still valid):

diyAudio - View Profile: jahonen

[tomtom]

thanks!

[oettle]

Originally Posted by mhelin

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) :
Index of /jahonen/Audio/DIY/DCX2496DinSRC

Third one which uses CS8416 SOIC part which is difficult to find these days.:
Improved digital input stage for the Behringer DCX2496

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.

[mhelin]

Originally Posted by oettle

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.

[mhelin]

Originally Posted by linuxworks

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.

[mhelin]

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.