Don Pearce wrote:

On Fri, 28 Apr 2006 15:36:00 +0100, "Dave Plowman (News)"
wrote:

True - I was just trying to correct your 1.2k, which while hardly a
typo was certainly a slip of the decimal point.

No - that's the input impedance of a Neve desk - one of the classic
designs. Others too. More modern ones may be higher.

Never knew that - thanks. I wonder why?


It is a balance between minimising the load on the the mic and keeping noise
under control. The optimum noise performance of the original descrete class
A Neve mic pres was about 4.8K. A 2:1 transformer gives you 6dB of noise
free gain and an input impedance of 1.2K plus all the other benefits of
truly balanced floating inputs.

Ian