Long S/PDIF leads.

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Long S/PDIF leads.

Post by Arpangel »

I dug out my old DAT machine yesterday, it was covered in mould, it was green, but it still works, after a bath in WD40.
I need it to compile tracks from old tapes, and it’s going straight into my interface via S/PDIF, owing to practicalities, it’s about 5 metres away from my interface, I’m sure this isn’t an issue, but can I just use a standard 5m phono lead, or do I have to have a fancy "S/PDIF lead"
I’ve tried a phono lead, and it works, just worried about possible low level drop-outs?
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Re: Long S/PDIF leads.

Post by ef37a »

Yes, you can get clicks and distortion if the cable is too long or has poor connections in the path.

Several years ago I experimented sending S/PDIF down long cables and found there was no problem with over 20mtrs of 'low loss' TV UHF cable. You need chunky plugs, https://cpc.farnell.com/neutrik/nf2c-b2 ... l2EALw_wcB

Don't worry about the solid core cable. You should not be moving it about a lot and in any case it stands a fair amount of abuse.

(I also found MIDI was fine over 40mtrs of twisted pair CAT5e)

Oooof! and ***k! Just seen the price of those RCAs! AFAICT you just need the size for cable entry. Gold plate is nice but by no means essential. I would look for something from 'Pulse Audio' e.g.

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Re: Long S/PDIF leads.

Post by Hugh Robjohns »

Arpangel wrote: Mon Nov 29, 2021 7:40 am... it’s about 5 metres away from my interface, I’m sure this isn’t an issue, but can I just use a standard 5m phono lead, or do I have to have a fancy "S/PDIF lead"
I’ve tried a phono lead, and it works, just worried about possible low level drop-outs?

S/PDIF was intended for short distant connections at the back of a hi-fi rack. The original spec suggested up to 1 metre. In practice it will go much further (5m should be fine), but only if you're using low capacitance, 75 ohm cable.

Standard analogue audio cable is likely to have quite high capacitance and you'd be much better off using standard 75 ohm video cable. You can buy ready-made leads with rca-phono plugs, or with BNCs to which you can fit bnc-phono adapters (I use the latter, so the cables can be used as word clock cables too).

A poor quality cable will either not work reliably, or it will introduce jitter and single bit dropouts which may not be obviously audible on music, but usually is with steady tones.
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Re: Long S/PDIF leads.

Post by James Perrett »

I have a few 5m S/PDIF cables here made up from 75 ohm co-ax with gold connectors. However nowadays I'd just buy budget video cables from CPC. Short ones are under a quid each and 5m ones are just under three quid.

https://cpc.farnell.com/pro-signal/psg0 ... =ac-152/bl

for example. (I use the 1m version of those between the DAT and minidisc machines and the patchbay).
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Re: Long S/PDIF leads.

Post by Hugh Robjohns »

Perfect!
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Re: Long S/PDIF leads.

Post by Martin Walker »

As the others have said, the important bit is 75 ohm video cable - and those needn't be at all expensive.

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Re: Long S/PDIF leads.

Post by Arpangel »

Thanks! I didn’t know any of this.
The problem is my Tascam DAP 1, the sockets are recessed, there’s not much gap around them, and you can only use phono plugs with thin barrels, the expensive ones are too thick, and only go in half way.
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Re: Long S/PDIF leads.

Post by ef37a »

Arpangel wrote: Tue Nov 30, 2021 8:04 am Thanks! I didn’t know any of this.
The problem is my Tascam DAP 1, the sockets are recessed, there’s not much gap around them, and you can only use phono plugs with thin barrels, the expensive ones are too thick, and only go in half way.

What maximum diameter plug can it handle Tony? I have a couple of good quality ones that are not too fat, you are welcome to them. You could either fit them to new cables or make up short adapters with line sockets. You can also drill/ream out smaller plugs to accept thicker cable.

FYI: I once enquired of Neutrik which of their RCA plugs were '75 Ohms'. "None" they said but said the 'miss match' was small and not a problem so long as the cable was 75R. For those here who may not know? BNC connectors can be had as 75 or 50 Ohm examples.

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Re: Long S/PDIF leads.

Post by Arpangel »

ef37a wrote: Tue Nov 30, 2021 9:30 am
Arpangel wrote: Tue Nov 30, 2021 8:04 am Thanks! I didn’t know any of this.
The problem is my Tascam DAP 1, the sockets are recessed, there’s not much gap around them, and you can only use phono plugs with thin barrels, the expensive ones are too thick, and only go in half way.

What maximum diameter plug can it handle Tony? I have a couple of good quality ones that are not too fat, you are welcome to them. You could either fit them to new cables or make up short adapters with line sockets. You can also drill/ream out smaller plugs to accept thicker cable.

FYI: I once enquired of Neutrik which of their RCA plugs were '75 Ohms'. "None" they said but said the 'miss match' was small and not a problem so long as the cable was 75R. For those here who may not know? BNC connectors can be had as 75 or 50 Ohm examples.

Dave.

Thanks a lot Dave, I’ll have a dive in my toolbox later, I’ve got a few phono plugs kicking around in there, if they don’t fit the bill, I’ll take you up on your offer, we’ve also got a conveniently large reel of 75 ohm cable left over from aerial activities!
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Re: Long S/PDIF leads.

Post by MOF »

Given that it’s a one off and that DAT machines aren’t heavy why don’t you move the machine close to the recorder.
I made up a 75ohm cable with gold RCA connectors when I used DATs and a computer.
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Re: Long S/PDIF leads.

Post by Arpangel »

MOF wrote: Tue Nov 30, 2021 12:08 pm Given that it’s a one off and that DAT machines aren’t heavy why don’t you move the machine close to the recorder.
I made up a 75ohm cable with gold RCA connectors when I used DATs and a computer.

The logical thing to do.

:D

Dave, I’m OK, I’ve taken the suggestion above, and I found an old 80’s "proper" dif lead in my cable box, and it fits.

:D
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Re: Long S/PDIF leads.

Post by Yearofthegoat »

I used an old 25m component video cable (used to send video to a projector in the days before HDMI) without issue, just to see if it worked. Bonus is you get 3 cables!

I currently have a 5m one linking my audio interface to an amp. It was easy to separate the individual cables, they just pulled apart. Nice to reuse old kit.
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