On Mon, 01 May 2006 12:29:45 +0100, Ian Bell
wrote:

Don Pearce wrote:


Thank you! I did make a gaffe. The actual figure for the Neve noise
figure is about 3dB. That is still unforgivably poor for high end kit
- it is in fact no better than my little Behringer. Ten years ago I
was designing satellite receivers working up at 12GHz. The noise
figure I was working to was 0.3dB.

The last audio preamp I made had a noise figure of about 0.5dB,
because I was willing to use multiple parallel discrete transistors
for the input circuitry. Making it any better than this would have
been possible, but unwarranted because unlike the satellite receiver,
it wasn't pointing at a cold sky, but a warm microphone.


Not that is really matters. An improvement in noise figure of 2.5dB will
only improve the signal to noise at very high gains by the same amount.
Unless you are using dynamics on very quiet sources, the self noise of your
condensor mic is the limiting factor not the noise figure of the mic pre.

Ian

True for condensors, but this was for a dynamic in a very quiet
situation. Generally when I am designing gear for myself, I see no
reason to make it any worse than I actually need to. I don't object to
spending an extra couple of quid for that, especially knowing that if
professional gear were made that way they would be charging another
ten grand.

d

--
Pearce Consulting
http://www.pearce.uk.com