Film-Tech Forum ARCHIVE: Source for a DB25 to 6 RCA cable?

This is topic Source for a DB25 to 6 RCA cable? in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Andrew Thomas (Member # 7000) on 12-29-2017, 07:07 PM:

I have a USL JSD60 and want to feed it 6ch analog from my Oppo Blu-ray player. Anybody know a source for this cable?

Posted by Leo Enticknap (Member # 534) on 12-29-2017, 07:41 PM:

We make them up for our installs, and am sure that we could do one for you. Contact sales [at] movingimagetech.com, or call 714-751-7998 if interested.

Posted by Derek Martin (Member # 7657) on 12-29-2017, 07:44 PM:

I got one for that exact job from Infinite Cables in Markham Ontario, works great. http://www.infinitecables.com/

Posted by Dave Macaulay (Member # 813) on 12-29-2017, 08:03 PM:

Not too hard to make for yourself if you can handle soldering to a DB25 connector, beware that cheap RCA-RCA cables have VERT thin wires that will be a bugger to work with. Or better music stores should have DB25-8xXLR cables (the JSD uses the THX pinout, might be identical to the Tascam pinout typical on music equipment - there's some confusion about pin 21), and you can get XLR-RCA adapters.
Best would be to call Odyssey Products and have them make one up. Mark knows the connector specs for pretty much every cinema audio device and they will almost certainly get it right.

Posted by Leo Enticknap (Member # 534) on 12-29-2017, 09:05 PM:

Rather than solder at the DB25 end, another approach would be to buy a parallel printer cable (if they are still made), chop off the DB25 plug at one end, add some heatshrink to strengthen the individual pairs and thicken them such that they can be held by the clamp in the RCA plug, and terminate them with RCAs. You'd need to continuity test DB25 pin to bared end of wire with a multimeter to figure out what color goes to what pin, though. Fiddly, but do-able, and probably less fiddly than soldering at the DB25 end.

Posted by Andrew Thomas (Member # 7000) on 12-29-2017, 09:35 PM:

I don't mind paying for a properly terminated cable [Smile]

Thanks guys!

Posted by Harold Hallikainen (Member # 5405) on 12-29-2017, 11:04 PM:

Remember that the JSD-60 has a differential amplifier input for the analog inputs. I'd run 2 conductor shielded cable to each RCA connector (+, -, shield) and connect the - to the shield at the RCA connector. Any voltage developed across the shield will then be subtracted out by the differential amplifier. Also, I believe the shield should be connected at both ends of the cable to minimize common mode voltage into the differential amplifier.

The same goes for the analog outputs on the JSD-60. They are servo balanced outputs that behave somewhat like a floating transformer output. If driving an unbalanced load, I'd wire it as above (2 conductor shielded cable with - connected to shield at the far end of the cable).

Harold

Posted by Brad Miller (Member # 2) on 12-29-2017, 11:59 PM:

We have those cables in stock if you need them Andrew.

Posted by Steve Guttag (Member # 268) on 12-30-2017, 08:01 AM:

We also make them (use Belden snake cable, AMP DB connectors with diecast shells and gold RCAs).

As for tying the shields in a 2-cond/shield wire, thre are two schools of thought here. You can just tie them at the JSD60 end and insulate them back at the Oppo end. This will let any noise drain at the JSD60, which will help keep a central point for ground. The Oppo's output is unbalanced but I believe iits chassis is grounded via the power cord (most consumer electronics have no real ground since they are only 2-prong devices but the Oppo has a 3-prong power cord). So, if the RCA connectors are tied to chassis, then I'd tie the shields, if they float off of ground, I'd fload the shields and let the JSD60 be THE ground reference for the shields. The differential input of the JSD60 only really cares about the potential difference on the two wires connected to them and will have a high CMRR. Tying the shield at the Oppo end is a matter of trying not to create a ground loop. The longer the cable, the bigger a deal this becomes.

I talked to Mark (Odyssey) at CinemaCon about making a breakout board. The idea was a DB25 to RCA (where there would be RCA connectors on the breakout board). Then one could run 3 or 4 stereo RCA cables (5.1/7.1). I don't know if he ever made it though. Since we make our own cables, the cost overhead of breakout boards typically exceeds our cost of the materials and then we can make the cable to any desired length (or even terminate on-site if we are running it through conduit since sometimes the Blu-ray player lives in the pedestal and we need to get the audio to the soundrack..