I was wondering if someone could tell me what went wrong, and if I have destroyed the mics internal pre-amp, or if I have just killed the capcitor in the battery box:
I have a Sony M10 recorder and was unhappy with recordings from a Audio-Technica ATR 3350 lavalier (too much self noise). So I bought a Sony ECM 88, after checking specs- it says 1 to 10 V on the web site specs. However, after buying it, the detailed manual says that it needs 5 to 10 V if used with a capacitor and resistor 3-wire battery box power, and the 1 V or more is when used with a transformer. And trying using just the 3 V plug in power, indeed the levels are very low, blowing on the mic is the only way to see a response (-35 dB or so) at full gain.
From manuals:
So, I build a 9V 3 wire battery box, as below, but without the pad on the right:
This works really well, low noise, perfect.
Then I try to be clever, and install a pad of around 8 dB so I can record a back-up track on the second channel at a lower level.
This obviously was not a good idea. For around 1 second, I get a signal like I expected, with the 2nd channel lower than the first, but then it very quickly started to generate a high level of noise. So I disconnect everything, and remove the pad resistors, now both channels come straight out of the DC-removing film capacitor. However, on trying this (effectively the same when as I had the battery box working), I get very high noise, and no response to sound (even gentle tapping). I was sure I had destroyed the microphone, but what gave me a little hope is that when using just the plug-in power of the M10, no battery box, the mic behaves just as it did before I built the battery box (blowing/tapping gives very weak signal at full gain).
But now my hope has been dashed, as I think it is probably the pre-amp, not the capsule I destroyed.