Optical to SPDIF ?

[Matthew Seed]

Hi guys I have a Fractal Audio Axe Fx II that I want to get into my new UAD Apollo Twin Duo. I would like to use an SPDIF cable but I have 2 questions.

1. Is there such a cable as SPDIF to Optical in. My axe fx is SPDIF but the UAD is Optical in only.

2. Whatever this cable ends up, I need it to be about 8 to 10 metres, is that gonna work at thT length and is it down to quality to make it work or would a budget cable work equally as well ?

Thanks guys.
Matthew

[James Perrett]

Yes, you can buy optical to co-axial convertors (they are both SPDIF) from places like CPC. I use a CPC optical to coax convertor which seems fine (although I've not used it at high sample rates).

I suspect that Hugh will know the exact figures but a 10m run should be no problem. I use cables sold for video use for my co-axial SPDIF connections and 5m long optical cables which came from Studiospares (as far as I can remember). Neither are particularly expensive.

[Matthew Seed]

Thanks James. So there is no cable that goes from one to the other it's more of a convertor needed. One more question then might be I know longer lengths of cables like this can be a problem, which out of the two would be the worst carrier.

Do would it best to get a 2 metre SPDIF and an 8 metre optical, or the other way round or each even length.,.. ..or of course am I talking rubbish and it doesn't make any difference.

Thank you
Matthew

[Hugh Robjohns]

Coaxial SPDIF was orifinally designed for short distance connections of less than a metre. It uses an unbalanced coaxial cable to carry a DC voltage toggling between 0 and 1V at about 3MHz. In practice coaxial SPDIF can be persuaded to run a few metres but with increasing jitter. High quality 75ohm coax works better than unbalanced audio cable.

The Optical version uses light pulses instead of a DC voltage, but the data format is identical. The quality of the light-fibre determines how far the signal can be persuaded to travel, and internal dispersion in the fibre leads to increased jitter again.

The cable/fibre induced jitter is only relevant if the cable/fibre is connected directly to a D-A converter.

In general, I've found that optical will travel further than coaxial with less signal degradation... But if you really need to get the signal over 10m it might be worth considering converting to the balanced AES3 format and back again. SPDIF-AES3 and AES3-optical converters are available.

H

[Matthew Seed]

Hi Hugh, thank you for helping out much appreciated.

I thought I'd heard that SPDIF was not meant to be too long. I might be able to get away with 8 metres wth a bit of re jigging. I'm not sure what AES3 is Hugh, sorry I'm not that techy when it comes to all this. If you had to get aN 8 metre signal out the back of a Fractal Audio Axe FX2 into a UAD Apollo Twin Duo what would you do? And if you could spare me time to tell which to buy I would really appreciate it ?

Matthew

[molecular]

I think your guitar processor has an AES out as well as SPDIF which would make life easier.

[Matthew Seed]

Thanks for the info. Again, not being that techy when it comes to cable technology AES i find confusing, is it an XLR jack on the ends. I think the AXE FX II has AES as an output but not sure if the UAD Apollo has it as an input, can't seem to read that anywhere. Is AES a better bet than SPDIF or optical cable then, would you say......if my UAD can take it that is ?

Matthew

[Hugh Robjohns]

This article explains the differences between the various forms of AES3 and SPDIF:

http://www.soundonsound.com/sos/feb07/a ... facing.htm

The optimum solution in your case depends on how much you want to spend. As I say, ideally I would use AES3 for the longer cable runs and convert as necessary at each end, but AES3 converters are generally quite expensive.

The Lake box below is one of the most versatile and cost-effective, but the Mutec is a high quality unit, too. ...but I doubt you want to spend this kind of money!



http://www.thomann.de/gb/lake_people_dfc_c430_formatkonverter.htm



http://www.thomann.de/gb/mutec_mc_11_2.htm

So... a far more cost-effective solution would be a simple Lindy coax-optical converter:



http://www.thomann.de/gb/lindy_audiokonverter_spdif_digital.htm

...and you would then either need a long coax SPDIF cable, or a long Optical one... I'd go for the longer optical cable option -- but buy a decent one. If it works, great, but it will depend to some extent on how sensitive and competent the digital interfaces in the equipment are. A friend runs two 10m optical fibres between his control room and machine room, and some equipment works with it, and some just doesn't!

H

[Matthew Seed]

Thank you so much Hugh for taking the time and that article has helped me better understand the differences too.

Budget is an issue unfortunately so i may go for the cheapest converter but spend as much as i can afford on the cables.

I guess with this option its a long optical and then just the shortest SPDIF i can find.

Would i be right in saying that my UAD Twin doesn't have an AES input option ? There is an AES output on the AXE FX so that would have been neat and simple.

As a final world would you still say a long optical / Convertor / short SPDIF would be a better bet than AES to AES or AES to convertor to Optical on the AUD (if the UAD doesn't accept AES) ?

Thanks again
Matthew

[ef37a]

If you can solder get some big, chunky RCA plugs from CPC and use low loss TV down lead (yes I know it has a solid core but he is not going to skip with it!).

I have used 20mtrs of that without bother and I only used the cheap, 15 quid converters both ways to get S/PDIF in and out of a Minidisc recorder and a 2496 soundcard.

Dave. (thought I had posted this a day or so ago?)

[Matthew Seed]

Thanks Dave. i don't think i should start making my own cables with my limited knowledge of what i am doing here.

I have just spent the last 3 hours rejigging my home studio setup and managed to get the distance down to 5 metres. Its not quite how i wanted to lay things out but with my concerns over this connection growing i wanted to shorten the gap.

Sorry to re ask the question but at 5 metres is Hugh's suggestion there still the best bet ?

Thank you for any help guys
Matthew

[James Perrett]

I use both 5m optical ADAT and 5m coaxial SPDIF connections from the studio to the computer in another room and haven't had problems with either type of connection.

[ef37a]

Thanks Dave. i don't think i should start making my own cables with my limited knowledge of what i am doing here.

I have just spent the last 3 hours rejigging my home studio setup and managed to get the distance down to 5 metres. Its not quite how i wanted to lay things out but with my concerns over this connection growing i wanted to shorten the gap.

Sorry to re ask the question but at 5 metres is Hugh's suggestion there still the best bet ?

Thank you for any help guys
Matthew

Well Matthew I disagree. I think you are at just that stage where you are moving out of "normal" setups and it really is a big advantage to be able to make and mend your own cables.
You also say "budget is an issue"? Now you will not save a great deal making your own leads, unless you want scores of them. but the ability means you can have what you need very quickly and precisely. Whilst it is probably true that ANY cable variant and "special" is available on the net, it can take a long time to find it and you can never be sure of the quality and value (i.e. you will get ripped for specials!).

Home recording used to be very DIY centred, the availability of ultra cheap, ultra high spec products (we would have KILLED for a 70dB noise floor 40 years ago never mind 100dB!) has changed that and I welcome the change but the "making and mending" skills will be lost at our peril IMHO.

Go-orn! Have a go!

Dave. (5+5mtrs should be fine BTW!)

[ed.king]

From my experience use optical for the longer run as recommended above, very important to get good quality cables especially co-ax for s/pdif.

[John Reid]

Matthew, just wondering if you realise that you would have to make the Axe Fx the clock master, which would mean you'd be condemned to running your lovely 192kHz Apollo at 48kHz?

[Matthew Seed]

Hi John, I know people will think I'm mental but I've always recorded at 44.1KHZ. I was aware of having to up that to 48 for using the axe fx though.

The honest truth is I have never fully understood the advantage of recording at the likes of 192 if it's going to end up at 44.1 in the end. I suspect I'm I'll informed on some benefits of this as I am well aware of the amount of pro kit that runs 192.

Bare in mind I am an amateur musician who records for fun.

Matthew

[molecular]

Hi John, I know people will think I'm mental but I've always recorded at 44.1KHZ. I was aware of having to up that to 48 for using the axe fx though.

The honest truth is I have never fully understood the advantage of recording at the likes of 192 if it's going to end up at 44.1 in the end. I suspect I'm I'll informed on some benefits of this as I am well aware of the amount of pro kit that runs 192.

Bare in mind I am an amateur musician who records for fun.

Matthew

Only some people will think you're mental. I wouldn't worry about it myself - I only ever record at 44.1 or 48, and those high end pro studios I have been in have worked at 44.1 or 48. The number of threads on here where the pros and cons get discussed must number in their tens if not hundreds, if you fancy digging them out and reading them. If I've picked up anything from those threads myself its that, apart from in some very specific circumstances, being able to record at 192 is way way down the priority list, below wearing clean underwear but possibly above making sure you don't step on any cracks on the way to the recording session.

[John Reid]

I intended less a discussion about sample rate and more on the point that the whole studio would have to be clocked by the guitar effects unit in order for the digital output to be used without sample rate conversion. Apart from questions around the quality of that clock, I think having digital I/O on an effects unit is only really useful if the effects unit can be a clock slave.

In the OP's case and based on what he's said though, there will be no issue.

[ef37a]

I intended less a discussion about sample rate and more on the point that the whole studio would have to be clocked by the guitar effects unit in order for the digital output to be used without sample rate conversion. Apart from questions around the quality of that clock, I think having digital I/O on an effects unit is only really useful if the effects unit can be a clock slave.

In the OP's case and based on what he's said though, there will be no issue.

I may easily be wrong here but! I seem to remember Hugh saying something to the effect that it is better to have your "worst" clock as master because the slaves will improve it?

Nearest analogy I can come up with is a TV sync "puller"?

Kevvy hat on.

Dave.

[Guest]

Any problem with using the analogue ins and outs? I had a similar situation going from a Kemper Coax to Babyface Optical, but in the end ditched it all for analogue after watching Misha Mansoor on YouTube recording using XLRs between his Axe FX and Focusrite Scarlett.

Wasted a bit of cash on cables and some cheap arsed converter beforehand though

[John Willett]

Hi John, I know people will think I'm mental but I've always recorded at 44.1KHZ. I was aware of having to up that to 48 for using the axe fx though.

The honest truth is I have never fully understood the advantage of recording at the likes of 192 if it's going to end up at 44.1 in the end. I suspect I'm I'll informed on some benefits of this as I am well aware of the amount of pro kit that runs 192.

Bare in mind I am an amateur musician who records for fun.

Matthew

Well - I was at a recording at Abbey Road with the LSO a few years back (I was a guest, not the engineer at that one) and it was recorded at 24/44.1 direct to Sequoia.

Higher sampling frequencies are used to minimise any filter artefacts getting down into the audible frequency range - which is why I normally use 88.2 or 96kHz, but don't see the point of going to 192kHz.

[Matthew Seed]

Thanks guys for the input. I think I might just use the analogue outs for now. It's proving very difficult and costly to get the digital signal safely across this distance.

I think I might stick with 24 / 44.1KHZ too. I've done a bit of reading and find mixed opinions on the pluses of recording higher than 44.1 that still relate to me.

Matt