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Behrigner DCX 2496 SPDIF input mod

Posted by Presto (A) on February 10, 2008 at 22:21:57

Hey gang:

I found this really cool site (www.dcx2496.fr) that has a bunch of very interesting mods for the Behringer DCX 2496 UltraDrive Pro. I thought I would try this SPDIF input mod first - it just made sense to properly terminate the SPDIF input to the standard with a 75 ohm terminating resistor and a couple of caps. I also skipped the connector, and hardwired the cable (!) directly to the chip socket using 2 short jumpers. I'll post a pic tomorrow. My IC socket is rotated 90 degrees from his, and I shorted 2 pin "pairs" for added connectivity. (I trimmed off 4 of the 8 pins, leaving the two that go to board traces on the 8420 and bended the other two pins so that I had 2 "free" socket points for jumper wires that go to the cable.)

I think there is no question this improves the jitter situation compared to to stock implemetation that has a few flaws for spdif, namely:

1) Runs spdif in using an XLR jack. Not 75 ohm characteristic impedance.
2) Runs though relay that flips from analog to digital
3) Runs through board traces on i/o board
4) Runs thruogh a ribbon cable (untwisted) to the DSP board
5) More board traces on the DSP board
6) Transformer has a 100 ohm terminating resistor! (AES/EBU value)

Six no-no's. Hmmm. And some say the digital input of the DCX has issues. That's a no brainer!

So I skipped all that and hardwired a cable DIRECTLY to the 8420 input terminals, using only about 1" of board traces from the old transformer location to the nearby 8420.

Now, I am still using the original 4 op-amp output and it still sounds... like a Behringer. But the SPDIF input mod is definately an improvement. Soundstage locations sharpened up dramatically, and edge detail has improved. There is MORE edge detail and texture with LESS shrillness and glare.

Thanks to the guy who made this very cool DCX mod site: Thierry Martin.
The site is mostly in French with some English pages available (translation under way).

I really recommend this mod. It took patience and I destroyed a few IC sockets customizing them (a few dollars worth) but I am really happy with this mod. Solder sucker, self-adhesive cable tie downs, and other tricks were needed to make a big cable sit in place and connect to a really small spot. I used scape capacitor lead jumpers from cable to IC socket allow a little bit of cable wiggle without tearing the IC socket loose or damaging the board or board traces. Delicate, but surely do-able. Most people would want to convert one of the input XLR sockets into SPDIF or BNC and wire a miniature coax to the socket. I plan to do that eventually myself, but not until I do the next mod - the passive output mod to bypass the existing rather cruddy output stage.

Have fun. And go slow.

Presto

Photo credits: from www.dcx2496.fr (by Thierry Martin)

• Cool DCX 2496 Mod Site by Thierry Martin   (Open in New Window)

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