Film-Tech Forum ARCHIVE: CP650 External Digital

This is topic CP650 External Digital - Coax Out from DVD in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Andrew Shingleton (Member # 2257) on 08-25-2004, 03:10 AM:

Hello all. We're planning on running a DVD player through our CP650's (all with the EX decoder). I've searched around and I think I've found almost all the info I need to do this, but I just wanted to check with the experts before I go and break something.

The easiest way that I think it can be done is to somehow connect the digital coaxial output on the DVD player to the I/O Connector on the CP650. According to the manual the pins required are 1 (AES/EBU Input -), 2 (AES/EBU Input +), and 15 (Chassis).

Am I on the right track here, or do I need to do something totally different? Any info on the exact way these need to be wired up would be much apreiciated. [Smile]

Posted by David Buckley (Member # 2600) on 08-25-2004, 05:35 AM:

Edit: Although whenever I've done this wirh stereo digital audio I've used a converter box (more expensive versions of the recommendation below) I've found a note that suggests that you can just connect he coax up to the AES/EBU input and it works. As the AES/EBU signal is phase sensitive not level sensitive, it doesnt matter which way round you go, just connect the '+' and '-', and leave the ground floating. Well worth a try.

And now the expensive solution...

The tool to convert from toslink or coax to AES/EBU is the M-Audio CO3 at $200 or under. You'll need to make up a cable to connect the XLR of the CO3 to the D type connector on the decoder. Pins are + Pin 2, - Pin 3, Gnd Pin 1.

However, although this unit will do the electrical and data format conversions between the consumer and professional formats, I dont know if the data produced by your DVD player will be acceptable to your Dolby decoder. I'd guess it would be, but dont know. If its not, then you are somewhat schtuck. If it is, you're home and dry.

Posted by Antonio Marcheselli (Member # 373) on 08-25-2004, 05:42 AM:

I've connected the digital out of my Pioneer DV 535 directly to my CP650/EX (as you explained) and it works with no problems at all.

Bye
Antonio

Posted by Steve Guttag (Member # 268) on 08-25-2004, 07:32 PM:

Yeah well, kinda sorta...no!

There is AES3 (aka AES/EBU) which is a 110-Ohm balanced twisted pair system

There is AES3-id which is a 75-Ohm coax medium using BNC connectors and is also a professional medium (hence it is AES3)

Lastly, there is S/PDIF which is also a 75-Ohm coax but it is a consumer medium that generally uses Phono (aka RCA) connectors.

TOSLINK is fibre medium that is strictly consumer.

The voltages on the various copper mediums are NOT the same...S/PDIF is the lowest at around .5V. AES3-id is nominal around a 1-volt and AES3 is up there with several volts (don't have the numbers handy)

If you are going from AES3 to either AES3-id or S/PDIF you can do it passively with inline type transformers (note, you have an impedance change plus a level change). Canarie and others make such units. Canarie even has one with an attenuator to knock down the level of the AES3 when it converts to AES3-id.

Believe it or not, the consumer S/PDIF and the various AES digital have different headers so there is no guarantee that cross connecting them will work with all equipment (but I haven't found the piece that didn't work and deal with quite a bit of level difference). A pro AC-3 decoder like Dolby's DP564 will read the header properly and know if it is a consumer or pro signal.

For more info on the AES stuff see Rane's excellent paper: RANE AES3 paper

Now back to your CP650 question...presumming you are not using the studio only Cat. 778 card which disables all analog outputs...you will find that on older CP650s (I wanna say it is the Cat774 card or so), there is a pair of terminals on the Option I/O port that are for S/PDIF or AES3. On the EX board inside are programable links (the board has to be removed from the chassis to get to the links). These links will allow you to properly connect you S/PDIF source to the CP-650 with the proper impedance and level.

On current CP650s there is a new board (Cat771, I think...it is actually a lower number than the old board). There are four S/PDIF inputs (no AES3) and you should make sure you refer to the correct pinout information since it has changed. S/PDIF 1 input is the one you want for AC-3 decoding from your CD player. Note, the Cat. 772 board with the crossover, also is S/PDIF only.

Steve

Posted by Andrew Shingleton (Member # 2257) on 08-26-2004, 09:25 PM:

Firstly, thanks to everyone for your replies and emails! [Smile]

I'm pretty sure I'll be able to do this with no real drama's now. We found an updated version of the CP650 manual (Issue 2 - we only had Issue 1A) which has a nice diagram about how to wire it up from coax and also illustrates where the jumper needs to be for S/PDIF.

One question though - I assume that after wiring the process up to a DVD player like this, running format 80 will result in 5.1 digital? That was my basic assumption, but it just occured to me that I haven't specifically read that anywhere.

Thanks again! [Smile]

Posted by Steve Guttag (Member # 268) on 08-26-2004, 09:39 PM:

Correct...Format 80 is "Master Digital" and will decode AC-3 or PCM as appropriate. You can also set the CP650 so PCM will be given a "Pro-Logic" decode or just left as a straight stereo Left/Right signal.

Steve

Posted by Andrew Shingleton (Member # 2257) on 08-26-2004, 09:51 PM:

Excelent! Cheers everybody! [thumbsup]