In rec.audio.pro, "David Grant" wrote:

I hope this is an appropriate news group to post this (I apologize if not)

Well first of all I'll say a bit about myself... I'm an electrical
engineering student with an interest in audio electronics. In the third year
of my program we covered basic amplifier design, which I loved, and I've
been considering a career in this field since.

At the moment I'm particularly interested in microphone preamplifiers since
I'm a poor student who has his own project studio, but doesn't own (and
can't afford) a nice preamp like the Great River.

I'm having a good bit of trouble finding any info on design strategies that
are specific to microphone preamps. I've found some schematics on the net
but there's rarely any very detailed explanation given about why they were
designed the way they were, and what considerations were made. I understand
all the basic principles like CMRR, slew rate, etc... but there seems to be
some sort of understanding gap, and I'd like to bridge that gap. I realize
it's probably something I'm not going to be able to grasp over night, I'm
just looking for some kind of direction.

If anyone knows of any resources that would help me, I'd appreciate it.

As others here have indicated, there's some good info out there,
you just have to dig a bit for it. Arny posted some commercial
schematics - the Rane uses the INA163 - I've used it as well as the
older (and slightly better and available in DIP thru-hole package)
INA103. Get the datasheets for these at http://www.ti.com. I've got
a design using it on my website.
These are 'basic' chips - Analog Devices have similar ones in there
SSM line. To get better performance (lower noise) requires discrete
transistors on the input, as I'm sure you know. The LM194/LM394
datasheet has a "High performance instrumentation amplifier"
schematic. I don't know how good it would be for a mic pre, though
with three of these devices for one amp, it looks like it's designed
to sell a large quantity of LM194's.

There's this Usenet post from John Hardy concerning the LM194 as
used in the 990:

http://groups.google.com/groups?q=+%...tbi.com&rnum=1

or:

http://makeashorterlink.com/?M2E8222B6

I've yet to ask him for his "data package," I suppose I should.

Thanks,

Dave

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