Why is s/pdif not so popular?

Starstreams

Starstreams

Member
Just curious why more external FX units and even interfaces don't take advantage of more s/pdif I/O on the back? I don't know if optical ADAT is considered the new alternative, but I've heard from a few people that it can suffer from jitter. I won't speculate on that because I don't know. But as far as s/pdif goes, it seems to work great for me. It not only transfer midi data, but my reverbs, delay and chorus's comes into the computer all digital with no conversion. And s/pdif does not seem to suffer from noise as it's just 1s and 0s going down the line.
It just seems like a no brainier to me, that s/pdif would be cheap to implement. If you're lucky most interfaces will give you one, some don't give you any. I know on my T.C M1 FX unit, you can assign 2 independent stereo channels with the correct FX routing with one s/pdif in-out. The Right and Left each go to their own engine in the M1 and then are summed into stereo as two separate FXs. If there were 2 or 4 s/pdif connectors on modern interfaces, you could have more external FX units coming in all digital.
I know software plugins are the popular thing today, but there is still a huge advantage to using external units with regard to taking a load off the CPU. Especially with dense reverbs.
 
You've lost me here. If it's digital out/in, then your original signal has already gone through the A/D in the interface. Now, it's going to a digital device for processing, which is different from a plugin in the DAW only if it goes through a D/A->FX->A/D sequence. Then I'd think you need a clock connection or master/slave configuration capability to keep things in line. Do external FX devices like that exist?

To me (not having used external FX), much of the value was in the analog-ness of those boxes, and hooking them up via patchbays, vintage style mixing boards, et al. And, if you've got modern Apple silicon (assuming that's what M1 is referring to), is processing power really an issue?
 
It's just ancient now - but TOSLINK was often regarded as having higher jitter. The trouble I suppose is that while great for 16 bit, the spec was originally limited to 20 bits, later extended to 24 bit, with some compatibility issues, of course, between equipment. Originally it was also a 2 channel format - and the ADAT version with 8 channels uses the same connectors but is different in protocol. I suppose now, we're supposed to use Dante for interconnectivity. S/PDIF was great 25 years ago(ish).

Making a new gizmo, and using a data transfer format so old, is a risky thing. Hence why pro gear now has Dante. More channels, less restriction on what the content is etc etc.
 
When I was transferring 8 tracks simultaneously from an 8-track portastudio to a standalone DAW that could record 8 inputs at a go, but only if you used S/PDIF {ie, 6 mic inputs, one S/PDIF}, it was worth its weight in gold.
My Akai has the option of going to another DAW either by analog or by one S/PDIF. I've found repeatedly that if I use the S/PDIF connection, I get this scratchy little noise. It comes randomly and it can barely be heard but I can hear it. Whereas when I use phono to jack inputs, I never hear it. So it's very rarely I'll use S/PDIF, although when it works, it works ! To me, it's just a tool, not a way of life.
 
@keith.rogers

If you're FX unit is digital, why would it go though AD into your computer? It's going into the computer (which is already digital) and then being mixed in your recording software digitally, then being converters from digital to Analog going out of your interface to your outputs/speakers. So I guess the interface needs to do the DA out the way out, but why on the way in?
As far as the clock. I have an RME UCX II which uses their newest clock-steady clock, The RME interface is my master and the T.C M1 xl FX unit is set to slave in (it's) I/O settings as the RME's clock is a better clock to clock from.


@rob I see what you means. I don't' know much about TOSLINK other then it's a different protocol going down the same cable. So it sounds like the clock was more the issue with TOSLINK or the clock? Some guys at the RME fourm were saying that jitter is not an issue with ADAT with RME'ssteady clock, which is being used on all their new iterfaces.

@grimtraveller
You're only getting two channels with SPDIF I guess. Someone at RME's post this.

ADAT = 8ch@single-, 4ch@double-, 2ch@quad speed
SPDIF = 2ch @single - quad speed (44.1 - 192 kHz)
Simply two different protocols over the same type of link.
 
I need to figure out why there is no edit button on this forum for me. I make a million typos. This sucks. Who is the admin?
 
Some of my SPDIF is electrical phono sockets, and some is optical.
The focusrite 18i8 shares both SPDIF and ADAT trough the same connector, and has difficulty making the ADAT work anyway.
I have never actually used SPDIF.

Whatever is an edit button?
 
Starstreams said:
@keith.rogers

If you're FX unit is digital, why would it go though AD into your computer? It's going into the computer (which is already digital) and then being mixed in your recording software digitally, then being converters from digital to Analog going out of your interface to your outputs/speakers. So I guess the interface needs to do the DA out the way out, but why on the way in?
As far as the clock. I have an RME UCX II which uses their newest clock-steady clock, The RME interface is my master and the T.C M1 xl FX unit is set to slave in (it's) I/O settings as the RME's clock is a better clock to clock from.

.....
Click to expand...
So, I finally understood that this "M1" thing is the TC Electronics M-ONE multi-FX box which does have S/PDIF inputs. I'm guessing you're using this with your RME, but I'd never heard of it.

I have used ADAT with my old Focusrite when that was part of expanding my inputs for mobile recording, but never used the digital I/O for anything else, i.e., like outboard digital I/O FX. For many *home recording* folks, I'd hazard that it's just a level of complexity that never found a market because lower end folks (like me) can manage with ITB stuff, or in some cases whatever internal FX available with some units (like the compression in my Steinberg I've used for live stuff a couple times). When you have to configure routing software and account for different clocks (or bit depth S/PDIF, a spec that is really *old* in the digital world!), that's a hard sell. And, if you want outboard stuff, it seems like that's where the direction is to go with analog devices. Just my (admittedly limited) POV.
 
Yes Keith.rogers. The T.C M1 reverbs, sound amazing for the price. Yes, everything connects via (one) S/PDIF in/out cable. Audio and midi all go thought his. I can use the XLR in and outs, but but I would still have to hook up the midi to automate the M1 in logic's environment. But the S/PDIF does it all.

Reguarding Toslink, ADAT, S/PDIF and Light pipe. I just learned something today. In case some of you are still learning as I am. Here is what I read from Sound Gear.

​

Don't confuse Toslink and lightpipe!

  • A normal Toslink is the optical version of S-PDIF or ADAT and only two channels.

  • A lightpipe, although it uses the same cable but different connector, is capable of multi-channel.


TOSLINK is a connection type. It is the same for ADAT and optical S/PDIF. While ADAT and S/PDIF are not compatible, they can both use a TOSLINK connector and cable. There are devices that can put both ADAT *or* S/PDIF through their TOSLINK connector, but it has to be the correct format on both sides (either ADAT *or* S/PDIF).

Coaxial S/PDIF is S/PDIF with an RCA connector, non-optical. Same format, different connection type.


Toslink is normally understood to be the optical version of S-PDIF, I described it as I did to make it clear; as just saying "Toslink" is confusing as S-PDIF down a Toslink lead is *very* different from a multi-channel lightpipe signal and totally non-compatible.
 

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That image is the back of my T.C electronics M1 LX
Sorry to have to make another post. I can't edit anything on this message board.
 
Another note that someone just corrected me on today:
TOSLINK is the connection type and you can run two types of protocols over this optical link (ADAT, SPDIF).
SPDIF protocol can also be transferred via copper -> coaxial SPDIF.

Also, I meant to say T.C electronics M1 XL above, not LX
 
Starstreams said:
Reguarding Toslink, ADAT, S/PDIF and Light pipe. I just learned something today. In case some of you are still learning as I am. Here is what I read from Sound Gear.

​

Don't confuse Toslink and lightpipe!

  • A normal Toslink is the optical version of S-PDIF or ADAT and only two channels.

  • A lightpipe, although it uses the same cable but different connector, is capable of multi-channel.


TOSLINK is a connection type. It is the same for ADAT and optical S/PDIF. While ADAT and S/PDIF are not compatible, they can both use a TOSLINK connector and cable. There are devices that can put both ADAT *or* S/PDIF through their TOSLINK connector, but it has to be the correct format on both sides (either ADAT *or* S/PDIF).

Coaxial S/PDIF is S/PDIF with an RCA connector, non-optical. Same format, different connection type.


Toslink is normally understood to be the optical version of S-PDIF, I described it as I did to make it clear; as just saying "Toslink" is confusing as S-PDIF down a Toslink lead is *very* different from a multi-channel lightpipe signal and totally non-compatible.
Click to expand...

I don't know where you are getting your information from, but Lightpipe normally refers to ADAT format signals going through Toslink cables and connectors. There are other optical formats like MADI but I've never heard of anything other than ADAT being referred to as Lightpipe. The cables and connectors for SPDIF optical and ADAT Lightpipe are exactly the same (I use both regularly).
 
I agree. I don't believe I said it didn't. ADAT on my RME can use light pipe.
A bunch of people at Gearspace said it
2-channel "TOSLINK" and 8-channel "ADAT/Lightpipe"

I said
  • A normal Toslink is the optical version of S-PDIF, or ADAT and only two channels.
  • A lightpipe, although it uses the same cable but different connector, is capable of multi-channel
So you're saying Toslink can transmit more then two channels? Everything on the net seems to imply that it's only two. But I guess it could be how it's implemented?
 
Toslink (Toshiba link) is the physical format, the optical cable and connectors. It can carry stereo S/Pdif or Lightpipe signal formats, depending on what the hardware is designed to accommodate. I'm pretty sure it can also carry Dolby Digital and DTS surround formats as well, if the hardware is meant for it.
 
Starstreams said:
Member John Willett said it at Gearspace and other's agreed.
Click to expand...
I've never used S/PDIF, but used a Toslink (ended) optical cable with ADAT many times (Behringer ADA8200 and Focusrite Saffire Pro). I think a lot of people are confused by the terminology, but it's the data format that is different, and incompatible, from how I read about this technology.

And, if you ever thought that this would be something the average consumer wanted to futz with, this thread alone should clarify why it's never gained traction...
 
@ jamesperrett
I was aware that ADAT and SPDIF was a protocol. But I see what you mean about the channels not being limited to Toslink. This is really new to me, what I said above was myself thinking out load as I'm learning.
I found this link below that explains the history. Looks like you can transfer 8 channels. Not sure why everyone out on the net keeps associating Toslink with only two channels. Even a google search does. but I think it's like Keith said, people get confused by the terminology and standards and the cable vers the connector.
Here is a quote from the link below that confirm
"The Toslink format had, until then, been used for carrying the stereo SPDIF digital audio format over optical cables. But Alesis adopted the format to deliver 8 channels of digital audio at 48K/24bit and was christened officially as the ADAT Optical Interface, and more commonly known at the time, as the ADAT Lightpipe." https://www.pro-tools-expert.com/production-expert-1/what-is-adat
 
The problem is that people don't know how to explain things correct. Now I'm confused. But when I figure it out, I'll explain it in a way that makes sense. Two many people out there on the net giving half ass and incomplete examples which leaves too much ambiguity. Now I have to re do all my notes.
 
And people are confused associating the connector type with channels when it's the speed that's the factor of channels.

With ADAT protocol, you can send 8ch, but only at single speed because otherwise the bandwidth would not be sufficient.
Therefore, if higher sample rates are needed, ports are multiplexed to achieve the higher bandwidth.
For double speed you need to "bundle/multiplex" two, for quad speed 4 channels.
Therefore, you have a variable number of ports with ADAT depending on the sample rate.

With SPDIF, where you have per protocol / design only two channels, the bandwidth is fully sufficient from single up to quad speed (44.1 - 192 kHz).
 
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