[Paul Stamler]

Meanwhile, when all the shouting dies down, and the distracting chaff about
low-noise-figure design has drifted to the ground, the input impedance of
*almost every* professional preamp sold in the world, bar the odd device
intended for ribbons, is 2.6k or lower. Period.

As for how many equations you need to compute the noise figure, yes, you can
do it with a single monster equation, but if you're writing a spreadsheet
it's easier to split it into two or three. Makes the proofreading easier.
One to compute the voltage and current noise, one to add that to the
source's noise (obtaining the equivalent input noise), and one to compare
the result with the source noise to obtain the noise figure. The advantage,
aside from being less unwieldy, is that you pop out both ways of expressing
the performance -- noise figure and EIN. Occasionally useful from a
human-engineering point of view.

Peace,
Paul

[[email protected]]

On Dec 6, 5:50 am, Eeyore
wrote:
Don Pearce wrote:
Read the title of the thread, will you?

The OP hasn't got a Hi-Z mic input nor does he need a Hi-Z mic.

Graham

The OP's PS5 only has approximately 40 dB of gain on the Line B 1/4 in
jack input. If the OP wants to use a Shure SM58 with -54.5 dBV/Pa he
might find the approximately 20 dB voltage gain from an 1:10 to 1:14
impedance transformer useful with his PS5. I believe the AT CP8201 is
a 1:14.

bobs

Bob Smith
BS Studios
we organize chaos
http://www.bsstudios.com

[Eeyore]

wrote:

Eeyore wrote:
Don Pearce wrote:
Read the title of the thread, will you?

The OP hasn't got a Hi-Z mic input nor does he need a Hi-Z mic.

The OP's PS5 only has approximately 40 dB of gain on the Line B 1/4 in
jack input. If the OP wants to use a Shure SM58 with -54.5 dBV/Pa he
might find the approximately 20 dB voltage gain from an 1:10 to 1:14
impedance transformer useful with his PS5. I believe the AT CP8201 is
a 1:14.

Loading that with 12k would hardly be very clever.

I never can really make out why this consumer crap is designed this way.
It would hardly have been difficult to organise a more suitable input
impedance or sensitivity, although I suppose the -40dBV was designed to
avoid easy overloading.

Graham