Alesis Multimix USB multichannel inputs

I have read the stickies on multichannel but the answers are a bit above my head!

What I want is to simultaneously record 4 mic inputs (vocals and acoustic instruments) onto 4 separate Audacity tracks for post-processing.
Do the cheaper ‘USB Mixers’ output separate channels to the USB port or does they simply output a single channel of the already mixed audio? I do understand that the USB wire has a single digital twisted pair, but are the digital audio channels multiplexed in packets? If so presumably it is muxed by the mixer hardware/firmware - is ALSA what decodes and demuxes the packets at the computer end?

Taking the Alesis Multimix 8 USB as an example, will it appear as a single device under preferences/devices/recording/device and I then choose
the number of channels I want, then add the same number of Audio Tracks?

Does the Behringer XYENIX range have similar characteristics to the Alesis? I have looked at both manufacturers sites and they do not explain.

Sorry if these questions sound stupid but I presently have no recording equipment and would like to know what is likely to work before getting any.


Are you using Linux?

My intention was Linux - Mint (Ubuntu), mainly because ALSA is open source unlike OSIO which I read requires writing code to be used with Audacity.
ALSA comes up as the default interface in Audacity Linux so looks like it might be straightforward - famous last words!

The number of channels available at one time depends on both the hardware and the drivers. As far as I’m aware, the hardware of the Alesis Multimix 8 USB supports 8 channel recording, but the Xenyx mixers only support 2 channels at a time (this will usually be the stereo mix of everything that is plugged into the mixer).

It is often reported that recording from multi-channel devices with Audacity will work with either 1 (mono), 2 (stereo) or all channels. For example if you have an 8 channel device and you wish to record 4 channels, then you may need to record all 8 and then delete the 4 unused channels. I don’t know why this is, or if it apply to Linux.

I don’t have specific information about which devices are fully supported on Linux, but if a device IS fully supported in Linux, then I would expect it to work in Audacity.
For multi-channel recording in Linux you should also look at Ardour.

Thanks Steve. It is difficult to know from the manufacturers’ specs which ones have multichannel outputs. I had to read through the manual to confirm that the Multimix 8 USB 2.0 does in fact have 8 channels output. The Multimix 6 and 4 USB do not seem to mention it. The Xynex specs also do not mention it so I guess you are right that they do not have it.
Strange that the info is so hard to find as I would think it is very important to know - as we are talking about two fundamentally different types of device.

OSIO seems not the problem I though as the hardware comes with Cubase software.

I would be interested to know what format/protocol is used to multiplex the multichannel signals - perhaps some USB version of MADI or ADAC?

I sent my questions to Alesis but so far no response.

Most multi-channel devices that allow simultaneous multi-channel recording will mention this as a feature.
Many multi-channel devices that only allow mono/stereo recording will “fudge over” the issue.
If it does not explicitly say that the device can do multi-channel (simultaneous) recording, then it probably can’t.

I presume that you mean “ASIO”

Sorry, I’ve no idea.

Got the following response from Alesis:

Just our USB 2.0 and Firewire Multimix mixers can output individual channels into the computer (and receive back a stereo mix into the mixer for monitoring).
The firewire mixers support sample rates up to 48k though the USB 2.0 mixers support up to 96k sample rates.

They didn’t answer my question about the multiplex transport protocol - perhaps it’s a secret!

Strange they call the whole range ‘Multimix’, even the models that don’t multiplex - the two types are quite different animals.

You are right Steve, if it doesn’t explicitly state then it is not multiplexed - though I had to dig into the Alesis manual to find out. You’d thing it would be a headline in their brochure.

The other way to go, I think, is multichannel preamp feeding discrete channels into a multichannel sound card, but looks like that would be a lot more expensive.

There are some multi-channel sound cards that have multiple microphone pre-amps built in. I think that Tascam make a relatively inexpensive USB sound card like this, but I’ve not used one and I can’t guarantee that it will work with Audacity.

Another option is that some mixing desks have “direct out” connectors that can be used to feed a multi-channel sound card. This is the method that is commonly used in big studios.

Yes the soundcard looks like a good option. M-Audio do a line of PCI cards with multi i/o including xlr breakout connectors.
I think you can input directly from mics and instruments to such a soundcard but I am wondering if there would be a risk of overloading the soundcard input amps, in
which case your idea of a mixer with direct output would be needed. But I’d prefer to do without an analogue mixer and do everything on the DAW.

As my setup will be primarily acoustic instruments I will need at first 4 mic inputs - 1x vocal, 2x piano, and 1x drums.
As most of the cheap mixers have two mic inputs I could add mic preamps as necessary, the outputs going to the mixer instrument input jacks. Does that sound OK?

Personally I’d prefer to spend a bit more money on the mixer and call it an “investment”.

The mixing desk is often considered to be the heart of a recording set-up and studios will often be designed around the desk with all inputs and outputs passing through the desk. Budget mixing desks not only provide less flexibility but generally have less good sound quality than more expensive desks. In the log run it would be more economical to get a mixing desk with 6 decent quality microphone pre-amps than to buy a cheap desk with two microphone pre-amps and then have the added expense of 4 more microphone pre-amps, and overall the better desk will be better.