I'm trying to find a compact, preferably half 19" rack sized unit that'll provide me with 16 analog outputs.. The underlying audio interface is not a problem since this'll be used in a custom code solution, but it ideally it has to be small and portable since it'll be used solely with a laptop.. I will be happy(ish) to use a 19" rack unit if there's no other option.. I guess a better description would be as long as it'll fit into a large laptop bag..

The closest I've found is along the lines of the Echo Audiofire 12.. Something like this with 16 outs (the inputs are irrelevant in this case) would be perfect.. But it has to be at least 16 outputs..

Audio output rates and depths are not important.. Basically 44.1K or 48K at 16bit is perfectly adequate for the task in hand.. Though if it supported higher rates I wouldn't be grumbling..

I've examined the RME solutions, but with their interface I understand that there's no daisy chaining of the IO boxes which would mean 2 cardbus devices and 2 IO boxes (Multiface II)..

Any suggestions, because I seem to be getting nowhere with this now..

Isn't it an idea to just take a Mackie Onyx mixer with Firewire card?
Those are available in many sizes.

What level are you going in at. If you are talking directly to the hardware you have very few options as virtually no one provides 16 out solutions which have open drivers or conform to any standard. If you are going in at the OS level (DirectSound/ASIO/CoreAudio) then of course it doesn't matter.

If you just need 16 outs and have money to drop then

http://www.apogeedigital.com/products/da16x.php

Symphony Mobile Express card would do it

http://www.apogeedigital.com/products/symphonymobile.php

It's a full 1u though not half and only works under Mac OS X.

However it's a full custom thing you need then

http://www.ioneconnects.com/

Might be what you want.

At the OS level (on Windows) with whatever audio API will be available, most likely ASIO as I want to keep the latency as low as possible..

That's exactly the kind of thing I had in mind, but the price isn't what I had in mind..
That is actually a beuatiful piece of kit, and I must stop looking at that now.. It's just way too expensive for what I had in mind..

The OSX only thing is a problem, I'm developing this stuff under Windows.. There's no real reason why I couldn't use OSX for it, apart from the fact that I'm much happier developing under Windows, both from an API point of view and from a development tools point of view..

I should have said that I didn't want to blow 1000s on this, but I didn't..

For now, just to get things up and running I've decided to grab a pair of M-Audio FireWire 410 and get going with them, which meet my form factor requirement (just) and will do the job for now..

This is only for my personal tinkerings, and I don't want to blow a fortune on this yet in case I get bored of it.. If things do prove fruitful then I think I will eventually grab the Apgoee DA-16X as that's absolutely perfect from the look of it..

I'm also tinkering with the idea of maybe just making a 16-output DAC box myself, based on some weighty microcontroller (maybe a strongArm or such like) and a bunch of multiplexed DACs connected either by USB or Ethernet to the PC.. Which would be a far sight cheaper..

They appear to be a bit overkill for the task, but can I send 16 channels out through those from the computer ?

You can.
Ofcourse you can go for the apogee solution which is suggested above, but it's MUCH more expensive and probably overkill for what you need.
If I may ask, what's the purpose for it?

I'll investigate those Mackies then.. But it's really a bit too large, but worth a look I think..

The goal is simply to build myself a surround sound rig so I can experiment with VBAP & Ambisonic type setups but within a musical context.. Also with the intention of doing a few live performances using the in-house PAs in whatever configuration can be utilised.. That's why I wanted something that was going to be fairly portable..

Well, the upside is that you can adjust the EQ on the mixer itself if you needed to (in live performances).
I use my Tascam DM3200 from time to time live.. But working digital (not having everything under your fingers directly) isn't ideal in a live situation.