The Akai DPS24's use of mixer groups is grounded in traditional analogue recording and offers great flexibility to the user.
I have bought an Akai DPS24, which is great, but I am having trouble getting signals to disk tracks. I previously owned a DPS12 and that was fairly simple, but the DPS24 manual talks about using 'groups' to route inputs to tracks. What is a group and how are they used?
Rupert, Bath
SOS contributor Steve Howell replies: This is a common cause of confusion when working with digital multitrack recorders. The mixer section of a digital multitracker typically has a number of inputs and a number of 'group' outputs to connect to the multitrack recorder. Each input channel has a collection of switches that allow you to route any one of these inputs (or, indeed, combinations of inputs) to any given group output (and hence track). So, for example, to route input channel 5 to track 3 of the multitrack recorder (MTR), you would assign channel 5 to group 3 — the signal comes in through input channel 5 and gets sent to group 3's output, which is connected to track 3 of the MTR.
This way, any input can be routed to any track without re-patching. However, to make grouping more versatile, many desks send signals out to group output pairs — 1+2, 3+4, 5+6 and so on. The principle is the same except that the input channel's pan control is used to send the signal to odd- or even-numbered group outputs. Citing the above example, to get input 5 to track 3, you'd route it to group 3+4 and pan the channel hard left; to overdub the same input onto track 4, you'd pan it hard right.
Paired output groups are also useful in that you can record multiple inputs in stereo, especially when recording multiple input sources. For example, you might have multiple mic inputs for a drum kit (or the line outs from a drum machine or sampler). The kick drum can go to track 1 (route the input channel to groups 1+2 and pan the input channel hard left); the snare can go to track 2 (route that input to groups 1+2 and pan the channel hard right); the hi-hat can go to track 3 (route that input to groups 3+4 and pan hard left). However, you wouldn't usually use separate tracks for every tom and cymbal. So, route the high tom input to, say, groups 5+6 and pan that some way to the left. Now route the mid tom's input to 5+6 as well but pan that central. Now route the low (floor) tom to 5+6 and and pan that some way to the right. The overheads can be similarly grouped and recorded to, say, tracks 7+8 in much the same way as the toms. If you are recording a live band with a bass player and other musos in tow, their instruments could be similarly routed to other tracks (again, via the groups).
This is pretty much exactly how the Akai DPS24 works. To get input 5 to track 3, press the 3/4 Assign button, press input channel 5's Select button and pan it hard left; to route it to track 4, simply pan it hard right. To get input 1 to track 8, press the 7/8 Assign button, press input channel 1's Select button and pan it hard right. In a similar fashion you can route any channel to any track.
Now, where it gets a bit tricky is that the DPS24's mixer only has eight (four stereo) group outputs to service 24 tracks. This is common on many mixers, and what happens in this case is that group outputs are 'doubled up', that is, each one is sent to more than one track. Let's rewind again to a more conventional studio for a moment...
This simplified block diagram shows a typical input channel in an eight-group mixer such as the one found in the Akai DPS24.
It was common practice (mostly in the interests of economy) to limit the number of group outputs. Thus, it was not unusual to use an eight-group mixer with a 16- or 24-track MTR. What you would do in this case would be to connect group output 1 to tracks 1 and 9 of the MTR (and also track 17 in the case of a 24-track). Similarly, group output 2 would be connected to tracks 2, 10 (and 18), group output 3 to tracks 3, 11 (and 19) and so on. So, to get input 5 to track 11, you'd route it to groups 3+4 and pan it hard left, before putting track 11 into record. This is the principle used on the DPS24. It can take a bit of head-scratching at first but the panel is labelled accordingly to assist you (plus you just kind of get used to it after a while).
You might still be thinking that this is unnecessarily complicated for simple track laying but it has many benefits. For example, we have already seen how we can combine several inputs to a pair of tracks. Well, the same principles can be applied to 'bouncing down' tracks, that is, mixing down several tracks onto a stereo pair of tracks. For example, you might have 18 tracks of backing vocals (perhaps for that Queen number you're covering!). To free up those tracks, you can bounce those down to a stereo pair using the groups in exactly the same way simply by routing the BV tracks to a group pair (panning each track accordingly to create a stereo image) and enabling the appropriate MTR tracks to record. The fact that the process is consistent for inputs and tracks means that once you've grasped the basic concept, it's pretty straightforward.
Groups can also be very handy during mixdown. By sub-grouping certain instruments and then routing those groups to the main L/R output you can be controlling the master level of a whole section of instruments with just one fader. All your keyboards could be submixed to groups 1+2, your guitars to groups 3+4, drums and percussion to groups 5+6, backing vocals to 7+8 with other primary instruments having their own individual channels. Thus you can control the overall level of these different instrument groups far more simply.
Take the time to digest the possibilities and flexibility offered by the use of groups. It's a time-honoured practice that has been the cornerstone of 'traditional' recording studios pretty much since the inception of multitrack recording. Fortunately, in the case of the DPS24, it's all very consistent and there are no special modes or pages you have to enter — it's all available from the front panel (almost exactly like a traditional console) and once you've got the hang of it, you'll find groups your flexible friend in the track-laying and mixdown processes!
If it's any consolation, you can route any given input to any given track directly using the DPS24's flexible internal patchbay (there's even a patchbay template for this) but this requires delving around in the Mixer mode's pages. The group facility, however, allows you to route any signal (or combination of signals) to any destination in a very 'hands-on' way from just the front panel.