On Tue, 23 May 2006 21:48:54 GMT, in rec.audio.pro "Paul Stamler"
wrote:

"martin griffith" wrote in message
news
On Tue, 23 May 2006 18:55:42 GMT, in rec.audio.pro "Paul Stamler"
wrote:

"Scott Dorsey" wrote in message
...
martin griffith wrote:

OK Scott, you win, I'll look for alternatives, its just to take a mic
and match it better to a NE5532. But size is important as I'm running
out of space, and I dont want to use a discrete input in this
particular case.

If you're wanting an ideal match for a 5532, you need about a 1:7
transformer. Jensen's 1:5 is genuinely excellent, bigger than the Beyer
but
way, way better-sounding.

I thought it was less than 1:7 for a 5532, I'll dig out the datasheet,
work out the noise formula stuff. I'll probably go for a COTS from
sowter, which are more easily available here

Typically you'd divide noise voltage density by noise current density to get
ideal source impedance. Those numbers are 5nV/rtHz and 0.7pA/rtHz
respectively, so you get about 7143 ohms ideal source Z. Assuming a 150-ohm
primary, this works out to a 1:6.9 transformer. The numbers are different
for a 5534a, but the ratio comes out about the same (1:6.83).

Peace,
Paul

Did the ohms law stuff as well :-) I will probably go for a lesser
ratio, more chance to play around with different loading R's etc.


martin