On Thu, 04 Sep 2003 19:10:39 -0700, Bob Cain
wrote:

What will the phantom resistors contribute?

That's a very good point. Since the phantom resistors
will be passing about 6mA each, they'll need to be up
to snuff, and well matched.

The thermal noise contribution of the total parallel
load resistance (phantom r's in series, preamp input,
and any shunt gain-set resistor in our project, all
in parallel) increases with the square root of resistance.
But gain, and therefor signal, increases linearly. So
we should go for as high a gain as practical for
lowest noise.

Using the 40mA/V FET's, effectively in series for
transconductance here, means a gain of R-sub-Total Load
divided by 50 ohms. A typical(?) load of 1000 ohms
means a gain of 26dB. A little more would be nice, but
tough to get.

The 20mA/V duals would only be 20dB gain. Maybe
enough; I don't know how to guesstimate it.

Is Scott Dorsey around? He could address that a lot more
knowledgably than I could.

And a lot of other things. Hey! Scott! Help!


Chris Hornbeck