Any ideas on this pre amp???

So I found this for $80 at my local surplus store...

Anyone know what its used for? can I make it a mic pre?





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I dunno. It says 'caution do not use with human subjects' on the front :shock: :green: maybe aliens then..

:wink:

It says 'caution do not use with human subjects' on the front

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Well, that still leaves death metal...

I know..whats up with that??? :shock:

the first gain stage seems to be a 2n5521 dual n-fet. I wonder if using both inputs would make it a balanced input? hmmmm

Looks to have been made in late 70s. 100 Meg inputs.. could have been used for galvanometric measurements like Ph and such. The warning against using on human subjects suggests it might have been used on animals for neurological tests. Things like evoked potentials in muscles etc. up to 300khz bandwidth is however a little puzzling in these applications, so , who knows ?

The filter sections in this kind of measurement equipment were usually made up of so called elliptic filters which have very steep cut-off characteristic, not really suitable for audio. Whether the filter section in this particular pre-amp is elliptic I have no idea but it is most certainly steep.

A wellbuilt instrument with a lot of salvagable hardware though.

edit: CMR (Common Mode Rejection) trim says the inputs A & B can be used together as differential input.

Abstract?The electrical conductivity of human cerebrospinal uid
(CSF) from seven patients was measured at both room temperature
(25 C) and body temperature (37 C). Across the frequency range
of 10Hz?10 kHz, room temperature conductivity was 1.45 S/m, but
body temperature conductivity was 1.79 S/m, approximately 23% higher.
Modelers of electrical sources in the human brain have underestimated
human CSF conductivity by as much as 44% for nearly two decades, and
this should be corrected to increase the accuracy of source localization
models.

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The Princeton Model 113 preamp was used for that.

WEIRD STUFF.
http://web.mit.edu/skkelly/www/Res/pitt95.pdf

At least they used a sample out side of body....

Hmm thats weird alright. I'm sure I could tap the input somewhere and make this a mic pre. it might have a really cool sound...


Thanks for all the info.. :grin:

Well 10Hz-10KHz is promising and it looks well made. I'd start by just sticking in a signal from a tape or minidisk and see what happens.

Good to see you here, btw. :thumb:

Stewart

looks likes sombodys cut my oscillorscope in half .

Lotsa cool parts. Hack it and use the box. I'm sure you could atract some death metal bands with that warning on the front.. :grin:

yea that box looks pretty cool... about the same size as an avalon U5

it says "see bottom cover" on the front.. what does the bottom cover say?

worse comes to worse atleast you can check the conductivity of your body :green:


I would probably start with the neighbors dog :razz:

Hi Bluebird!

How are ya' man?

You always come around with the coolest stuff. :grin:

When you become a famous producer/engineer, perhaps that will be your trademark box.

Take care,

Dean

Hi Dean! Hi Zebra!

Dean did you ever make your passive mixer?


Yea my girl friend wants me to make a lie detector out of it... :shock:

WOW I soldered and XLR at the input and tested this with a 421 mic and its sounded really cool.

because of the impedance being wrong it lacks a little low an all but it has TONS of gain and sounds crispy like my 1272's. The frequency roll offs ARE very steep but sound neat.

I'm just gonna have to find a good spot to stick an input TX.

Anyone have a Schematic for a animal brain conductivity amplifier? :grin: :grin:

Dean did you ever make your passive mixer?

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Nope, how bout' you? I'm still looking forward to giving it a go.

I've got parts collected for a passive mixer, G9's, SSL comps, API 312's, Sherlocks, etc. I need need to point this computer monitor at the wall for a while so I can get to work!! :green:

Dean