Help needed expanding from 12 to 24 outputs!

Posted: Mon Jan 22, 2007 10:32 am

Hi everybody, I am the on-stage engineer for my band and I would like to probe your minds for some advice please!

We have an M-Audio Projectmix I/O optically connected to an 8 in/8 out Behringer Ultragain ADA8000. In addition to this we also have a 4 x stereo channel headphone amp for on stage in-ear monitoring. The equipment is configured for a live band setup utilising Ableton Live for backing track and track automation/FX purposes.

We have 7 inputs plugged into the Projectmix direct from the guys on stage (2 x Stereo Guitar, 1 x Stereo Drum Machine and 1 x Mono Bass). The main vox and 2 x backing vox go direct to FOH, then the FOH engineer sends me back a return on an auxillary channel which I use to feed into the backing singers in-ear monitors (powered by the headphone amp). Overall I am controlling 4 seperate monitor mixes plus the main instrumental mix which gets sent to FOH as a stereo signal.

The reason it's all set up this way is because I am on stage, not FOH, so I cannot monitor the vocal levels in relation to the rest of the music. As the sound levels from the instruments are fairly consistent, it makes sense to allow the FOH engineers full control of the vox and the mix between the vox and the stereo feed of the music. This makes sure the FOH engineer is always able to control any mic feedback issues. However, we would like to give the FOH full control of the whole mix - but only after is has been processed within Ableton.

At the moment, the equipment we have is limited to 12 outputs (4 on the Projectmix and 8 on the ADA8000). These are all currently used in the following way:

Projectmix output 1/2: Main stereo output to FOH
Projectmix output 3/4: Bass heavy monitor mix for drummers bass-shaker unit (shakes the stool so drummer can 'feel' the beat)

ADA8000 Outputs 1/2, 3/4, 5/6, 7/8: Individual in-ear monitor mixes for the guys on stage

What I want to do is expand our total outputs to 24 so I can actually send each instrument channel to FOH *AFTER* it has been processed with Ableton (very important!) and this is where I am having difficulty, because I know how the sound should be routed, I'm just unsure of the best way to acheive it.

The most direct solution would be to find a 24 channel output digital AD/DA converter with mic preamps. This unit would also need to be able to handle ADAT optical in/out so it can be synced to the Projectmix. Does anyone know of a unit that meets these requirements?

The alternative would be to slave another couple of ADA8000's, but I don't think it's possible. Again, can anyone clarify if there is a way to do this?

I hope there is a genius amongst you that can help!

Thanks!

Posted: Mon Jan 22, 2007 11:35 am

The ADAT lightpipe is specified as 8 channels at 44.1 or 48KHz and pro-rata fewer channels at higher sampling rates. This means that an interface with more than 8 channels (such as the Creamware A16 Ultra) has more than one set of ADAT lightpipe connectors, and hence that it makes little difference whether you get 16 or 24 channels in one box or use separate 8-channel boxes.

I think you will find that your problems are at the driving end, not at the AD/DA end. I don't believe that a single M-Audio ProjectMix I/O will cope with your expanded requirements, and if you throw that load on to the PC that's running Ableton, you will run into severe latency issues.

From your description, Ableton is producing the backing tracks and also the automated level processing on the main channels via the ProjectMix. If you want to expand this set-up, my advice would be to continue to keep the main signal paths out of the computer, and perform any required track processing externally. You could consider a digital mixer for this job. A Yamaha 02R96 would work well but is expensive; the 01V96 would be fine sonically but you would have to drive the automation from the PC as it lacks built-in automation. With either, you would get a few local analogue mixer outputs and then need 24 channels of DA conversion via 3 external boxes fed from ADAT lightpipes to send to the FOH, in-ear monitoring or whatever. You would also get at least 40 input channels via this route. You keep the PC doing pretty much what it's doing at the moment, but you may have to program the MMC for the mixer automation by hand.

For live sound (as opposed to studio recording), the ADA8000 probably gives you adequate sonic quality. The Creamware unit would be a step up in quality, and there are other interfaces to consider from MOTU, Alesis etc.

Posted: Tue Jan 23, 2007 6:02 am

Thanks for your quick reply Boswell, what you've said makes perfect sense. I suppose the only other (cheaper) option would be for me to sit out front next to the FOH desk with all stage inputs/outputs running down a multicore into the Projectmix. That way I could submix FOH via the Projectmix and still have the main outputs running out of a stereo pair into the main desk. It's food for thought - thanks for your help!

Posted: Tue Jan 23, 2007 6:34 am

Just one more question regarding this Boswell, the Projectmix has S/PDIF coax and ADAT optical input/outputs connections on the back. Is it possible to utilise both of these technologies at the same time so we could have 8 outputs on the ADAT bus and 8 outputs on the S/PDIF?

Posted: Tue Jan 23, 2007 12:30 pm

S/PDIF is only a two-channel data stream. However, from a quick read of Projectmix manual, you can't output different channels down the ADAT and the S/PDIF - you have to select one or the other as the output destination.

Posted: Tue Jan 23, 2007 12:39 pm

Thanks Boswell, I've learnt something new today! Smile

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