[Elecraft] Bias and Dynamic Mics

[Bob McGraw - K4TAX]

While I agree with Jim, K9YC on this.  Some dynamic mikes I've 
encountered do use a transformer to get the voltage level from the very 
low impedance Z element to a respectable output value.  Running a bit of 
DC through the transformer on the secondary side could tend to cause 
some DC saturation.   And transformers which are not designed to handle 
DC can behave a bit odd under this condition. Other dynamic mikes I've 
encountered provide an internal DC blocking capacitor to prevent this 
issue, although that in itself has its issues.

Yes, with any dynamic mike being used, set the bias to the off 
position.......just to be safe.    And don't worry about overloading a 
dynamic mike, but do be concerned with the preamp or first analog stage 
being driven into distortion.

73
Bob, K4TAX

On 11/4/2015 7:54 PM, Jim Brown wrote:
> This is one of those ideas that, while having a solid theoretical 
> basis, doesn't hold up once you plug numbers into the problem. That's 
> because the bias voltage is typically provided from a rather high 
> impedance source, so the bias current is too low and the sound 
> pressure level is too low to drive the diaphragm anywhere near its 
> limits.