From: Joav Shdema
Hi Bob, Some discussions on the audio mailing list left me wondering should I make some changes to my audio cabling – regarding the digital audio transfer. I have searched your site, and others, but could not find a satisfying answer to my quest. Today I am, as most others , using 75ohm cables for S/PDIF and 110ohm cables for AES at 16/44.1 What are the recommended cables for 24/96 digital audio, are they different from the former and in what way (width, length, material, connectors, whatsoever), is there any new standard or practice I am not aware of?
As a producer/engineer who slowly make the transpose to higher bit and sampling rate – doing it right from the beginning is very important to me. Best, Joav
Desert Island Productions
As we move into 24/96, the integrity of the interfaces becomes extremely critical, the quality of the cabling, the length of the cabling, and impedances, voltages and connectors. There are only two high quality routes to go with, depending on your ingenuity.
The RCA connector is bad. It is not true 75 ohm. The voltage on S/PDIF is specified as 1/2 volt p-p, which does not survive long. Better to raise to 1 volt p-p. The XLR connector is bad—it is not true 110 ohm. Reduce the number of either connector in your system, and the performance improves, particularly at 96 kHz. I have seen some marginal connections that lock perfectly at 44.1, marginally at 88.2, and not at all at 96 K.
A router like the Z-Sys or the NVision is highly recommended. It will support all rates. By using a router, your connections get shorter and cleaner. The Z Sys can be outfitted with either BNC’s (AES -3 ID) or XLRs. With BNCs, you use low loss RG-59 U, BNC’s everywhere possible and convert all of your interfaces to 75 ohms. If possible, increase the output voltage of all your S/PDIF sources to either 1 volt p-p or 2.5 volts p-p, so they will survive cable routing longer. That’s the route I have taken.
Or with XLRs. In that case, I recommend Belden media-twist 110 ohm cable. It has the best bandwidth, reduction, and performance at 110 ohms. You can find further details on this topic at the mastering webboard website.
Hope this helps,