Film-Tech Forum ARCHIVE: Extending Dolby Digital cable

This is topic Extending Dolby Digital cable in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Matthew Taylor (Member # 2310) on 08-01-2011, 04:41 PM:

The Dolby Digital cable that connects my FP30 to a CP500 is quite short. I figured that I could extend it by using a standard 25-pin printer cable where the pins follow through exactly.

The trouble is, it seems that the blocks aren't being read accurately and I get a 'F' reading all the time. Why would this be? Could it be because the cable isn't correctly shielded?

Posted by Steve Guttag (Member # 268) on 08-01-2011, 04:58 PM:

Not just that...it isn't correct on many counts! Not in impedance, current carrying...and so forth.

In the typical cheeseball DB25 extension cable you have some really small gauge wire (maybe 30awg) with an overall shield.

In the Dolby reader cable, you have 22awg twisted pair cables (x4) with individual shields plus TWO overall shields (foil and braid).

If you use the real stuff (Belden 8164) , you can go hundreds of feet.

I'm sure someone in the UK, like Bell can get you what you need and it will work.

-Steve

Posted by Matthew Taylor (Member # 2310) on 08-01-2011, 05:20 PM:

Thanks Steve, that definitely makes sense. I'll get some decent cable.