At 5:49 PM +0000 8/12/09, Greg ODrobinak wrote:
> Dan:
>
>I am not sure where you would get 12VDC from the internals of this
>unit. The battery pack outputs 9VDC nominal and the external supply
>is good for 5VDC, so there is obviously some DC power conversion
>happenning, but we don't know what the voltage rails are without a
>schematic for the unit [does anyone have this? I would LOVE to see
>it!]. Also, some microphones are finicky, such as the Okatavas, so
>they really need to have 48V.
>
>I suspect that Zoom restricted the phantom power to 2 inputs to keep
>power consumption down to a minimum. Assuming that a microphone
>draws 4 mA of power at 48VDC, then the power needed is 200 mW. This
>would translate to roughly 23 mA continous draw on the battery pack,
>taking the inefficiency of the power conversion into consideration.
>This is significant for long-term recording when you are relying on
>AA batteries for power. If you are using 8 mics which draw 4mA each,
>then our power requirement jumps up to almost 1.6 watts. We don't
>often realize how much power our mics really use and how it impacts
>our power source! Some mics take as much as 8mA which would double
>the power budget to 3 watts. There go the batteries!
One can buy 4-Rolls PB224's or Art Phantom II's for $50-70 each and
remove them and squeeze them into a much smaller housing that uses
XLR pigtails to the mics but useful only if the R16's pres are
workable for you and that's a big "if." You are right that phantom
supplies can use a significant amount or current. The Rolls and Art
have coax's for 12 volt sleds (negative center! btw).
...
>Also, if someone could post the procedure for doing the self noise
>measurement on an arbitrary recorder's mic preamp, I would be most
>grateful. I have an idea of how to do it, but I am not certain that
>my procedure is correct.
I'd like to learn about how to do this right as well. Rob D.
>
>Thanks!
>
>-Greg O'Drobinak
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