SPDIF cable

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Armistice

Armistice

Son of Yoda
Not sure where to put this so I'll chuck it here...

I'm going to attempt to connect a couple of components via SPDIF - both have in and out SPDIF connectors, which appear to me to look quite similar to RCA connectors.

I'm wondering what to connect them with...

From my googling, I'm seeing that there appear to be both optical and "coaxial" type cables. The optical cables have a specifically shaped squared off on one side circular connector and an optical bulby thing at the end. The coaxial type cable seems to just be a normal metal connector.

I'm assuming I'm thus talking about using the standard cable, like this (which I already think I have one of, somewhere) rather than an optical cable like this - sockets for which I'm seen occasionally on the back of stereos and TVs.

Here's the back panel of one of the devices.

Am I on the right path here?

Cheers dudes...:thumbs up:
 
The ADAT IN in your link to the Fireface is the toslink (optical input). You can actually see the light coming out of the cable when connected at one end.

The other type is actually the same as the RCA cables used for VCR's and Tape decks. Showing my age. At least I didn't say 8-track tape and Betamax. lol

The two are completely different animals. That link (optical) makes the cable look similar, but if you saw one in person, you would quickly see the difference.
 
jimmys69 said:
The ADAT IN in your link to the Fireface is the toslink (optical input). You can actually see the light coming out of the cable when connected at one end.

The other type is actually the same as the RCA cables used for VCR's and Tape decks. Showing my age. At least I didn't say 8-track tape and Betamax. lol

The two are completely different animals. That link (optical) makes the cable look similar, but if you saw one in person, you would quickly see the difference.
Click to expand...

I've seen them both in person Jimmy...:D I'm just trying to work out which one I'd be using...

So, more info... I'm not talking about the ADAT in/out on the Fireface, but the SPDIF ones at very top right.

I can't find a pic of the other unit at good enough resolution to be certain but I found this on the spec: "S/PDIF In/Out 44.1 kHz (24 bit) with RCA Phone connectors (Master only)"

Which leads me to believe I would be using the coax type cable/s to link from it to the Fireface, rather than the optical ones... I don't think you use actual RCA cables for this, but 75 ohm coax cable - I'm sure I bought a "SPDIF" cable years ago in an ill-fated attempt to connect a multi effect guitar unit direct to my old standalone recorder.. :eek:

I remember it being purple. Shouldn't be hard to find in my black cable world, if I still have it... :D

Make sense?
 
I have never had an issue just using a typical RCA cable. Not the super cheapies that you find with old shitty audio gear though. Just decent quality one.

Never heard of using coax cable for spdif. It is just a standard RCA cable man. Sure you could find a $200 gold plated one, but it won't sound any better. It is just a digital signal. :)
 
That back panel has both optical and coaxial spdif. The coaxial spdif is an RCA connector, but you want to use a cable designed for video. The cheap RCA cables that come with stereo equipment are not good enough, even though they may work in a pinch.
 
Farview said:
but you want to use a cable designed for video.
Click to expand...

Yup, this. But I have used cheapo RCA cables and didn't have a problem. Albeit, cable runs were only 2m. When I had my Lavry's, I used the Toslink optical cables, only because I had them laying around. I never noticed a difference in performance either way. SPDIF is only 2-track, so not a heavy load.
 
Thanks gentlemen! As I suspected, and I'm sure that's exactly what I've got in that purple cable I bought 10 years ago... great big thick thing, sold as a video cable.

The other unit only has coax ins and outs, so that's what I'll be using.
 
I stand (well sit) corrected as far as what is best.

I have only used 3' RCA cable for a preamp once. Never had a issue. Best to go with the recommended cable. And the purple cable sounds sweet! :D
 
Farview said:
The coaxial spdif is an RCA connector, but you want to use a cable designed for video. The cheap RCA cables that come with stereo equipment are not good enough, even though they may work in a pinch.
Click to expand...

This. Any RF grade RCA cable should do whether it's video cable or made specifically for SPDIF. Sometimes you ca get away with audio grade cables, but RF grade is less prone to problems.
 
For SDIF I have made some cables using RCA plugs (good metal ones) and some 75 Ohm Coax like used on TV antenna. No problems at all. At a pinch a good RCA audio cable can be used, but if you are planing a permeant connection make the good cable.

Alan.
 
Bandwidth isn't the problem, frequency response is. A spdif signal is a very high frequency signal, compared to audio, so you need something that will pass frequencies that high. Cheap audio cables are not designed to pass that high of frequencies, that's why it isn't recommended.
 
I have used odd audio leads for S/PDIF connection without problems but yes, if you have the choice, do it right!

TV downlead is ok but a bit clunky. It is normally sold as "low loss" UHF cable but you don't need to run over half a gig! Seek out some thinner VHF radio cable but make sure it is of 75 Ohm impedance and not 50 Ohm as used by the "ham" fraternity, satellite and the Rubber Duck Brigade.

You will find it virtually impossible to get a cable with a stranded core but don't worry! Solid cores are pretty robust and in any case you don't generally thrash S/PDIF cables about? Get some nice big chunky RCA plugs and Gold don't hurt, super to solder!

Note that the S/PDIF protocol was intended for "consumer" connections over quite short distances? Two mtrs is probably a decent maximum.

Ah! Wiki states a max run of 10mtrs for S/PDIF but it is probably best to keep things as short as practicable.

Dave.
 
Thanks all, as I said earlier, I thought I already had a proper coax cable, purple, which I've managed to locate:

Cable.webp :D

And the two units will be on top of each other, so no great length is required, anyway...
 
The trouble with coax transmission is that the cable characteristics tend, as mentioned, to degrade the signal, with the usual length limitation of 10m on a proper 75Ohm connection - over this length the square waves start to look quite un-square, so the error rate creeps up, and eventually crosses the 'can't correct' border. The optical system also suffers from losses, especially if the thin fibre gets bent sharply.

All this said, I just use whatever cables I have laying around - and none of the decent ones I have cause problems up to 6m. These will sometimes work if I use two and a coupler, in an emergency - but the normal and very common hi-fi types that are 1.2m long all work.

50Ohm coax actually works pretty well, and the impedance mismatch has very little impact.

I still have a DAT machine that has SP/DIF and a readout of error correction status, and the changes in cable type make very little difference to the error correction until you try the skinny and very long cable, when it jumps up. I've got around 10m between two of my rooms and can send it down the patchy cabling fine, with a jack to phono at each end.
 
Well there you go. I learnt something. I've looked at the Sp connections on my stuff and just shrugged. Didn't seem to need it so didn't bother to find out about it. Now I know something. I don't know whether I need it though.
 
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