I've just figured out how to run my Alesis MMT8 of batteries!!
This is one of the Holy Grails of the MMT8 - the ability to power it off 9V DC voltage! I looked at the schematics today and figured out where to connect it up, and it works!!
My MMT-8 is an older version grey model that has the early mini-phone jack power socket. I've noticed that the circuit board on the newer, standard plug-pack connector MMT8's is slightly different to mine in parts positioning, and at the moment I haven't been successful in getting these later model ones to work properly with this mod. So for the moment, this mod is only for the EARLY MODEL MMT8's with the mini-phone power jack.
I estimate that you could run it on 6xAA alkaline batteries, or 8x rechargeable AA's (rechargeables have slightly lower voltages, so you need an extra 2) for quite a while - maybe 10 hours constantly. It pulls about 290 mA. I've installed 8x 1.2V Ni-MH AA's rechargeables in it and put a charging socket on the back panel of mine!
I've uploaded the Illustrated guide for the MMT8 9V DC mod to the Yahoo MMT8 forum, in the FILES section of the site.:
You could probably get better battery life by running it directly off 4.8V-worth of NiCads and bypassing the voltage regulator. You may need to do something clever around the memory protection circuitry, otherwise it might not bring the RAM up correctly.
It's a shame the HR16 is so tight for space inside - it wouldn't be hard to do the same trick for that. It doesn't draw a lot of current on its +/-12V rails. They're only used for the output amplifiers and DAC, which draw a few milliamps at most.
According to the schematics, it runs a +10V rail to the processor for power up and reset. Dunno if that means you really need 10v, or whether any nominal DC pulse will reset and initialise the processor on startup. 8AA batteries still isn't a hassle to fit in the MMT8 - it's almost empty compared to the HR16. And mine has been running for ages on the same alkaline AA dry cells
Portable battery powered setups are valuable to certain people - for a variety of reasons. Convenience (just switch 'em on, any time, any where), security in a power failure (battery kicks in if mains power dies), street performances/busking. But the main reason for converting the MMT8 to DC power is to have an alternative power plug pack to the stupid Alesis AC 9V wall wart. You can now use any DC 9V, 500mA adapter.
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