Battery powered?

[Revren Jesse]

Does anyone know if it's possible to power any of the pre's using battery power? Like 3 nine volt batteries in series for 27 volts? Or maybe you would need 2 sets of batteries for +27 volts and -27 volts... I think the average nine volt produces 1500 mA, but it's been a while and I can't remember... which would seem to produce about 4.5 amps from 3 batteries. I guess I was just wondering if its possible to make a small portable 2 channel version that would run for a couple hours off batteries. Of course, some kind of 'radio shack' case wouldn't have mu-metal shielding, etc., does anybody think this is workable?

[dkatz42]

The good news is that you wouldn't need fancy shielding with a battery supply.

The bad news is that batteries are rated in amp-hours, not just amps. If a garden-variety battery could supply sufficient current, it wouldn't do so for very long.

I've used pro video camera batteries to field-power a Metric Halo ULN-2 (which presumably has its own internal DC-DC converters to step up the voltage) which is probably along the lines of what you'd need to provide the current for long enough. You'd have to fashion your own DC-DC converters to provide the +-27 (and the -48 for phantom power if you're using it.)

Sounds like it would be a fun project for the motivated. The lesser motivated might want to look at some of the available field preamps (like the Sound Devices stuff.)

[tele_player]

Or just get a ULN-2.

[dkatz42]

Yeah, the ULN-2 is a very nice package, with decent pres and very good converters. It even survived a bunch of sea water once (unlike my laptop.) Don't ask.