It ain't an API or Neve .... but probably a bit better than the pres found in most small mixers.

I don't remember what the 312 did for a power supply. I think I recall it's internal and therefore probably small and being run at its max capicity.

The 312s were TASCAMs high end offering for the 8 track narrow guage recorder, the 80-8 they were producing at the time.

The major problem with these boards is the power supply, that they don't offer phantom power and they run at a nominal -10dB on unbalanced rca outputs. It would put a huge strain of the output amps to drive a balanced +4 input to 0vu (-16 digital scale). You would have problems interfacing comps and processors that run at +4dB as well.

A basic no frills mic pre like GTs "The Brick" will deliver better performance.

It is internal power supply, but it does have switchable phantom power for each pair of channels. Probably beats out the Eurodesk that i use for live sound when it comes to adding some pres... anyone else have any info...? thanks

I owned one of these for a while. There were tow models.M312 and M312B.I believe the 'B' designates 'balanced'.This board has 1/4" and XLR connections,phantom power and decent quiet preamps.Its probably a LOT better than most Mackies in terms of depth and separation of channel cross-talk.The caps do dry out as with all electronic equipment and at the age its at it could probably use a cleaning.All of these basic maintainence items will most always determine the sound quality of a piece of gear.
Its been a large number of years since I used one, but I do remember it being a decent sounding board with a limited EQ section and not a lot of routing choices.It was easy to use and the monitoring was separate buswise from the mix or the recording bus.I wont comment on the +4/-10 operation as I dont think I had any +4 outboard gear at the time and I simply dont remember and I dont want to get into any pissing match about something like that.I used it exclusively with my 3340 Tascam 4 track machine.