Can an 828mkII play nice with an 8m?

[RodneySauer]

I am using a new MOTU 8M for my 8-channel recording studio (using the ethernet connection to the Mac). I left my old 828mkII attached via Thunderbolt-to-Firewire, since it's convenient for MIDI, and its extra channels are handy.

But I've had a few glitches where DP decided that the old 828mkII should be the "real" audio interface, and changed all of the inputs and outputs in a project from the 8M to the 828, and I had to select each input and output and set them back to the 8M. So I'd like to unplug the 828 from its Firewire cable, and have it just send digitized audio via an optical cable to the 8M, and let the 8M pass those signals along to the computer via ethernet. I realize I'll lose MIDI, but my keyboard can use USB MIDI instead.

My question is: if I attach the 828 to the 8M, how do I tell it what audio channels I want sent along the optical cable? The manual says it sends 8 channels of audio over optical, but it doesn't say which (there are 10, if you count the 8 channels of line-level and the two front preamps). Also, do I need to attach a Word Clock cable so that the 828 can sync to the 8M's clock? Is that just a standard RCA cable, or something fancier? Or does it even matter for recording, since the 828 won't be used for playback? Does the optical cable carry clock timing?

The manual is not good at explaining this, and the "MOTU Audio Setup" application that launches when I turn on the 828 doesn't give any options on what gets sent by the optical outs.

Thanks for any help (or even just pointing me to links that explain how to do this).

[mikehalloran]

There's more than one way to hook things up but, not having an 8M, I don't want to waste your time.

I would call MOTU support or submit a tech link.

[wylie1]

If you use the 828mkII as your main plug in your 8m to the 828 via ADAT optical DP will show you have 16 inputs.
8-16 will show as ADAT inputs.

[RodneySauer]

Okay. I think the next thing is to just "plug things in and see what happens." And then I'll call MOTU.

[wylie1]

Good stuff, what I told you was basic the 8m has allot of new tech MOTU may have a better set up to get more out of the 8m.

[RodneySauer]

Right: I know that the 8M has cool ways to link the new modules... but I'll be linking some old tech to it. I'll report back when I see what happens.

[HCMarkus]

That 8m should be connected via Thunderbolt for best performance, yes?

[RodneySauer]

That 8m should be connected via Thunderbolt for best performance, yes?

That's the weird thing. Ethernet is much older and cheaper and runs long cable lengths, but it transfers lots of data very fast. The specs look very good either way -- especially with at most 18 channels, which is the most I can do with these two units. (In fact, the ethernet protocol is how multiple AVB interfaces send audio data to each other, since Thunderbolt is less flexible.)

[wylie1]

Have you got everything online yet.
I'm wondering how you've set it up.

[HCMarkus]

That 8m should be connected via Thunderbolt for best performance, yes?

That's the weird thing. Ethernet is much older and cheaper and runs long cable lengths, but it transfers lots of data very fast. The specs look very good either way -- especially with at most 18 channels, which is the most I can do with these two units. (In fact, the ethernet protocol is how multiple AVB interfaces send audio data to each other, since Thunderbolt is less flexible.)

As long as you are not worried about throughput latency, Ethernet looks great but, last time I checked the really long thread over at BeerGutz, for fastest response when recording VI's or monitoring audio thru DP, Thunderbolt was the clear winner.

https://www.gearslutz.com/board/music-c ... rface.html

Just an FYI; only you know what is the best choice for your workflow Rodney.

[wylie1]

I didn't think the 8m would have all the DSP effects in it but it looks like it does so you might be better to use the 8m as the main and plug the 828 into it.
there maybe pros and cons ether way I'm just guessing.

[RodneySauer]

I've been busy on other projects, but I made some progress on using my old 828mkII as external A/D converter to add more channels to my new 8m today, so I thought I'd post.

I connected the optical out from the 828 to one of the optical ins of the 8M, using a standard optical cable.

My plan is to have the 828 independent of the computer, but you have to edit its internal routing while it is connected to the computer via Firewire.

In the MOTU Audio Setup utility, set the 828's Optical Outs to ADAT (might as well set optical ins to None). If you use TOSLink, you only get two channels, while ADAT gives you eight.

Also, select 44.1 or 48 kHz, to match your 8M's speed. At higher frequencies, ADAT can't handle eight channels; you're on your own for that.

Then start up CueMix to tell the 828 which channels you want to send out via ADAT. Since the ADAT protocol only handles eight channels, and there are ten channels in the 828mkII, you'll have to give up two of them.

The key to getting this to work was finding this Motu tech note. Note, though, that those instructions are for D/A, and we're doing A/D, so you want to do the opposite of what is described (as they note in passing at the end). Here's my shorthand version of the set-up.

In CueMix, Combine all of the channels to stereo pairs (whether or not you'll be recording in stereo; this is just so you can get eight channels onto four buses).

Set the Mix to Bus 1, set output to ADAT1-2. Max the gain on the channel pair that you want to go to the first two ADAT channels, and mute all the others.

Set the Mix to Bus 2, set output to ADAT 3-4, and repeat the step above for the next pair of channels. Same for Buses 3 and 4.

I decided to send Mic/Guitar 1-2 to ADAT 1-2, and then Analog 3-4 to ADAT 3-4 and so on, so that the numbers stay somewhat logical.

Now you can quit CueMix and unplug the firewire cable from the 828mkII.

In the 8M's routing page, send ADAT A1 (along the top of the table) to AVB Stream 2 1 (along the left), send ADAT A2 to AVB Stream 2 2, etc. through ADAT A8 to AVB Stream 2 8.

In Digital Performer, assign your new channels to the track you want to record to. DP uses a different numbering system, where AVB Stream 2 1 shows up as 8M:8M 9. In the 8M's routing I'm hearing a bit of static that I need to trace, so I may be having issues with clock (or possibly my Ethernet cable is loose). I was hoping that the 8m could slave to the 828 (since that's the way the optical cable is going), but it doesn't give me an option in the Configuration settings to do that; so maybe it can't put a clock signal on that same cable. I may need to use another cable of some kind for clock sync. Any hints along those lines would be welcome.