8-channel microphone preamplifiers tend to be 'workhorses'. If you want a special sounding preamp, you would look at a single channel model, perhaps the likes of the Universal Audio Solo/610 vacuum tube model.
8-channel preamps on the other hand tend towards neutral and everyday. As long as they are transparent and of professional quality, it is mainly the range of facilities they offer that would make you choose one over another.
The PreSonus DigiMax FS does of course have eight microphone inputs, conveniently mounted on the front panel. It uses Neutrik Combi connectors so that jacks can be inserted for instruments and line sources.
The first two channels are high impedance and therefore suitable for electric guitars. The rest are standard line-level inputs.
You can use the DigiMax FS as a purely analog preamp. It has eight analog outputs on the rear panel, on jack connectors. This is in contrast to a unit like the Focusrite Octopre where the outputs are on a far-from-convenient 25-way connector.
The DigiMax FS also has two ADAT outputs. You can use this at the conventional sampling rates of 44.1 and 48 kHz. Or you can use the S/MUX protocol to achieve eight channels at 88.2 or 96 kHz, four channels per ADAT output connector.
ADAT outputs are convenient because even though the ADAT digital tape format is long gone and not missed, the ADAT light-pipe is a very convenient way of getting digital signals from one point to another over short distances.
There are also, surprisingly, two ADAT inputs. Why would you need ADAT inputs on a microphone preamplifier? Well, you might want to use the unit as a digital-to-analog converter. It has eight DAC outputs. Well, you might – you'll know yourself whether this will be an important feature for you.
Of course, the DigiMax FS will sync to external sources, either via a BNC connector, or to an incoming ADAT signal.
There is one point I really like about the DigiMax FS – eight insert points, one per channel.
Now this is a point that is often missed on 8-channel microphone preamplifiers. If you are working with the analog outputs, then it doesn't really matter as you can place any processing you need between the preamp and the recorder.
But when you are working digitally, this opportunity is lost. So yes, this is an excellent feature to have on standby.
Two gripes. One is that the maximum gain is only 55 dB. Granted, if you go beyond this you are probably amplifying noise. Even so, a pro engineer always wants to have a little extra on top of what he or she would expect to use.
The other is the external power supply. The art of encasing power supplies internally has been fully mastered by most manufacturers. So why not here?
In conclusion, a solidly performing unit with a good range of facilities.