[sdiy] (Semi-OT) cap polarity in microphone

[Ingo Debus]

Happy Harry wrote:
> 
> If the bias on the preamp side of the cap is higher than
> the mic bias voltage... its correct.
> 
> If not it is an assembly error. Measure the DC on both sides
> with respect to ground, and decide...

This depends on where the mic is plugged in. The plus side of the cap is
just connected to the output of the mic.

Plugged into a normal mic input, the cap is reverse biased with 1.5
volts. When plugged into a "plug-in-power" input with a voltage higher
than 1,5 volts, it's forward biased. Perhaps they thought, better have
it reverse biased with 1,5 volts (normal input) than reverse biased with
an unknown voltage (plug-in-power). The two devices with plug-in-power
inputs I own (a camcorder and a MD recorder) have 2,5 volts. Are there
inputs with higher voltage?

Ingo