Advice on the 1248

[sebner]

I am currently using the 828 MKII interface with DP7. I am contemplating upgrading to the 1248 based on wanting to increase my sample rates (would like to record at 24bit/96KhZ) and increase the number of monitor mixes for my studio from 4 to at least 6 ( I like to record as live as possible in the studio). Right now I am able to create 4 stereo mixes and use the main out for a 5th mix. In looking at the manual and other documentation on the 1248, it looks like i will be able to get at least 6 independent stereo mixes of all the inputs, be able to record at 24/96 with 8 analog inputs and using the 8 adat inputs, plus 4 mic preamps, and 2 high impedance inputs if necessary. Is this accurate? It looks like at higher sampling rates I would not be able to use all of the inputs and outputs in the adar/spdif banks. But it does say there are 7 aux sends int he mixing section. I wonder if they are including the spdif as assignable to one of these aux mixes. I am guessing I would have to convert the spdif output to analog to use it as a separate mix ( I can do that now I think). Any thoughts?

[TinenTech]

I'm still trying to figure out the feature set myself from the literature.

It's pretty clear that the AVB mixer in the new MOTU interfaces can provide 14 Aux signals, configured as 7 independent stereo aux sends. The two front panel PHONES jacks appear separately in the matrix, so you have two right there. The 8 rear-panel analog outs will take care of 4 more stereo headphone mixes, for a total of six stereo headphone mixes. (You still have your Monitor Out for control room speakers, and a main out.)

You could also assign Aux sends to the ADAT output pairs. Here the issue is your sampling rate. The two ADAT Optical output ports can handle 16 channels at 48kHz (8 ch. per pipe) or 8 channels (4 ch. per pipe) at 96 kHz, using the "SMUX" method. The stock chips for ADAT I/O were designed for a maximum 48k/8 ch., so they're doubled to go up to 96 kHz.

The trick, if you use the ADAT Optical outs at 96 kHz, is how are you going to convert them back into analog for the headphones? There are lots of SMUX A/Ds (mostly in 8-channel mic preamps), but I'm not aware of a standalone SMUX D/A converter.

If you have an old ADAT you can leave in REC/INPUT mode, or an Aphex 141, or an old Alesis AI-3, you'll get 4 outputs/2 stereo mixes from each. (Channels 5-8 will just sound like a copy of 1-4.) To get 4 more outs, you'll need another ADAT/Aphex/AI-3.

Unless...and this is a guess...MOTU's "type II" does the ADAT optical differently, with all eight channels sending on each pipe, even-numbered samples on one pipe and odd-numbered samples on the other. Anyone (If so, a single ADAT D/A will give you your 8 outs.)

Technically, whoever's listening on those ADAT outputs isn't getting the benefit of 96k recording in the headphones, but the session will still be recorded at that rate. (Most headphones don't go beyond 18 kHz anyway, so it's unlikely you'll hear the difference there.)