A bit OT: I want to build a portable micpre...

[Coriolis]

I'd like to build a portable micpre for my minidisc, that runs on a single 9V battery, and prefreably one with a balanced input. Having trouble finding the right schematic though, either they're unbalanced, or they're for 15V bipolar supply. Tried ESP and a lot of the other sites. Any ideas?  I'm using it with an audio technica condenser which has a battery supply, so no phantom power.

I guess I just need to know about the right building blocks and component values, something opamp-based, but all the possible configurations are pretty confusing!

Anybody?

C

[ejbasses]

Try searching for differential input op amp applications.

[Rochey]

Just a suggestion - use 2x9V batteries, and connect them so that the earth in the system is the -ve of one battery and the positive of the other.

you should then have plus and minus 9V supply.

then, take the circuit from: http://focus.ti.com/lit/ds/symlink/ina163.pdf

and voila... one preamp to go

Cheers

R

[Coriolis]

Thanks for the quick answers people!
Rochey, that's a great all-in-one package in that pdf, but do you think I can get good results with +/- 9v, when the schematic says 15v? If there's a little less headroom, I can live with that, but will it still work?:?:

Man, I gotta start checking out datasheets looks like that's where the good stuff is!  

Regards,

C

[Rochey]

From what I can see, it's a headroom thing.

The amps will run from +-4.5V to +-18V. If the 9V is too small, use 4 pp3's  for +- 18V! :lol:

That many cells should give you a good battery life as well.

Let us know how you get on.

Cheers

R

[Coriolis]

Thanks again Rochey!
Well I was hoping to fit it all into a 1590BB, but that might be difficult with
4X 9v... :wink:
Hmmm.....Anybody had luck getting samples of those chips, I mean, do I have to make up a fake company name and pretend to be an EE to get a couple freebies?  :lol:
Edit: I just ordered me some free samples from TI! Hope they find me eligible...

Regards

C

[MartyMart]

Thanks again Rochey!
Well I was hoping to fit it all into a 1590BB, but that might be difficult with
4X 9v... :wink:
Hmmm.....Anybody had luck getting samples of those chips, I mean, do I have to make up a fake company name and pretend to be an EE to get a couple freebies?  :lol:
Edit: I just ordered me some free samples from TI! Hope they find me eligible...

Regards

C

Dont forget that this op-amp is "Surface mount"  !! ie: very very tiny!

Marty.

[Rochey]

surface mount really isn't as big a nightmare as you may think it is.

I've mentioned this before - and i'll say it again - prototyping on PCB is nowhere as expensive as it used to be. With lots of online companies doing complete boards for $25, surface mount is not as scary as it used to be (unless we're talking tiny resistors and capacitors).

I don't see why you couldn't put a tiny dollop of glue under the chip to hold it in place over the pads, and then solder.