> 1. Could using a regular dynamic mic really damage my 702? Before
> I saw the warning in the manual, I tried a regular mic and it seemed to
> work OK (but occasionally there was a lot of static -- could the power
> supplied by the 702 have built up somewhere and then discharged, causing
> the static?)
A dynamic microphone has a small coil of wire attached to the diaphram.
This coil moves through a strong magnetic field to generate the output
voltage. This coil will obviously conduct DC current, and will present
a much lower resistance DC path than the FET, so the 702 will supply
much higher-than-normal current, which will certainly shorten the battery
life even if it doesn't damage things. The static probably is the result of
small changes in resistance during slight movement of the plug which normally
would not cause a problem, but because of the high current, they create
enough voltage change to hear.
Bottom line: pay attention to the warning! If you want to use a dynamic mic,
place a capacitor, say 47 uF/16 V in series with the hot lead (+ to the 702,
- to the mic) to block the DC.
> 2. Is it OK to use an electret mic that takes a battery? I'd think that
> with the battery in, it would "look" like a regular dynamic mic to the
> unit, so would present the same danger that the manual warns against.
> I'd also think that with the battery out, there would be an open circuit
> so the FET wouldn't be powered.
Should work OK, because most mics with the battery in the plug have
a series capacitor to keep the DC out of the recorder input. The best
way to use such a mic however, is just to cut off the plug (containing the
battery) and replace it with a normal (non-battery) plug that fits the recorder.
Since the recorder already has the circuitry for powering the mic, you'll
eliminate the duplicated circuitry in the battery plug.
BTW-- The power circuitry for electret mics generally consists of a series
capacitor (47 uF/16 V, + to the mic, - to the input stage of the recorder) to
block the DC. A small resistor 1.5K to 2.7K is connected from a DC
voltage source to the mic to provide power.
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