Spdif/jack/ardour woes

Signal chain usbInterface/Alsa/jack/Ardour/mixbus

I just cannot use the analog outs on my keyboards as they sound sooooo much better with spdif.
Unfortunately I also have to use ADAT on my interface to add more inputs, so as soon as I use ADAT then spdif doesnt work as you have the option between one or the other.

So, my question is; did anything new appear on the horizon to enable me to route spdif via a separate interface into Ardour/mixbus ?

What it basically will entail is a spdif to usb device in conjunction with the usb interface that has both to be routed into Ardour.
As I understand that has not been possible in the past to route two usb sound sources into Ardour as Alsa apparently develops a migraine when it needs to clock and sync twop streams of usb data.
Anything changed allowing it?

There are ways to do it, but they are all outside of Ardour, and require some more advanced setup typically. For instance if running Jack you could utilize alsa_in and alsa_out to route to and from the second interface with resampling to match the different clock. Catch is always that you have two different clocks, which is less than ideal to put it mildly. You would be better off utilizing an interface that handled this for you rather than doing a bandaid on your system but to each their own.

      Seablade

With jackd I think zita-a2j would be the recommended solution over alsa_in.
If jackd is not needed for routing between applications, I believe the ALSA backend in Ardour includes the same capability now.

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Also note than since jackd 1.9.18 there is an internal zalsa_in/out client which incorporates the zita-a2j function into jackd. That feature has been available in the jackd v1 branch for quite a while, but has finally been incorporated into jackd v2 as well. Version 1.9.18 was released in 2021 April, so should be available in most distributions by now. I think using the internal client should probably become the default recommendation. I need to experiment with that a bit so I understand how it works and don’t give out incorrect instructions. As of 1.9.18 the CLI switches for loading zalsa directly when starting jackd had not been added, so you have to start jackd, then just jack_load to load the zalsa client:

jack_load zalsa_out -i "-d hw:Mio"

There should also be arguments available to specify sample rate, period size, etc. to the client, but those examples were not given in the 1.9.18 release notes, hence the need for a little bit of research and experimentation.

If only only need separate devices for Input and Output, Ardour’s ALSA backend allows this

However with the GUI you can only pick one device for Input and one device for output.
If you need multiple input and/or multiple output devices at the same time, some manual settings are required. see Multiple mics on Ubuntu - #2 by x42

Seablade:
I understand the clock issue therefore I mentioned it explicitly.
The reality is very different.
If you have e.g. four or more keyboards that you want to all link digitally, then there is no solution with what is currently available with interfaces. No interface I know of has a spdif mixer, where I can add several spdif keyboards. the Roland spdif mixer is obsolete and unobtainable and there is nothing modern that replaces it. Using that, at least I get an spdif mixer with usb link to the workstation. So the problem is having to USB sound sources as mentioned. Everyone seems to be using analog outs these days and that is a HUGE sound quality hit on keyboards w.r.t spdif.
It seems the industry is devolving regarding keyboards.

Robin & Chris.
I will have to read up on your suggestions.
A2j custs all my other applications midi capability.
So unless there has been a change that wont work either.
That results in maybe solving the spdif issue, but then cutting all native USB to applications as that then will go through alsa/jack it seems.

I’m not sure what you mean there, can you explain?

There have been almost no “S/PDIF mixers” ever, in the sense of devices that have more than one S/PDIF input or output, and this is for a very obvious reason: the format was specifically conceived of as a stereo “final” format, which is why digital mixers tend to have only a single S/PDIF input and a single S/PDIF output (if they have either). Muxing together lots of S/PDIF signals just isn’t a thing that has ever been remotely common in the audio tech industry.

There have not been many keyboards with S/PDIF output, either. Things haven’t “gone back” to analog outs - they never really moved away. Starting about 10 years ago, we started to see keyboards/devices with their own USB audio connection (even mixing consoles), and because of the way things have gone, this is now the common format for digital i/o with external devices like keyboards.

Shows how long it has been since I needed such a solution:)

Seablade

Just a quick glance. Certainly a small portion of the market, but solutions do exist, however you still need to make sure you maintain clocking throughout, something S/PDIF and ADAT are not particularly strong for for the record.

I would disagree with this actually, a lot of larger arranger workstation keyboards came with ADAT and many could be switched to S/PDIF IIRC, especially if geared for live usage. This was particularly popular with the last gen of keyboards, maybe two gens ago. USB interfaces only take you so far on the stage.

That being said I agree with the rest of your statement outside of stage use. Funnily enough even those keyboards that HAD ADAT or S/PDIF I don’t know that I have ever seen more than one person ever utilize them:)

   Seablade

Fair point. I was mentally focused on coax S/PDIF and forgot about the toslink version.

Still, not many mixing consoles had “large numbers” of toslink connectors either.

That is VERY true, and probably a large part of why I never actually see those keyboards with this functionality actually use it:)

   Seablade

Anywhere I know of this being done, there is a sample rate conversion stage before mixing in digital format. For example, the audioscience audio interface cards that feature aes3/spdif inputs has SRC on each input (defeatable if the devices are synced) before the mixer stage.
This would have the exact same effect as using a second spdif interface running through zita-ajbridge.

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