Need a good portable (battery) stereo pre for mini electrets

What's a good, simple, but decent mic pre that will work with stereo panasonic electret capsules? I need to feed the signal to line level portable dat or minidisc, but the on-board pre is less than stellar.

It must be operated by battery (2 9v would be 18 volts right?) operated, and it must be able to provide at least 9vdc to the mics themselves.

I have been mounting panasonic electrets in Jabra cell phone ear-gels, and the binaural recordings I am getting are amazing. far more realistic than those made in the Nuemann dummy head.


In fact, with the right headphone levels, if you sit in the exact position the recording was made in you can't tell what is real and what has been recorded. Even a knock on the door in the other room is processed by your brain as such!

the only thing keeping me from using these babies to make some seriously cool music effects is the fact that the recorders preamp sucks, and I can't think of a decent enough cheap and portable battery operated pre (except for spending $600+ on the Sound Deviced Mix Pre).

Any ideas?

Shane

How about a modified green pre. Since I don't need 48v maybe I could get away with using 2 9v batteries.

KDMP! and four 9V batts.

HTH!
Charlie

Since I assume you're using the Panasonic capsules unbalanced, you can roll your own pretty simply. An NE5532 or an OPA2604 can handle both channels, and either chip will work fine from +/- 9V.

If you have no intention of converting this/these mics to balance/phantom operation then I think a dedicated gain to suit might be a better bet.

FET might be the go.

:roll:

... re-make the onboard pre ...

I can't easily remake the on board pre since it is sealed in the little tin can surrounding the capsule. I did try to cut one open with an x-acto one time, but to no avail. If anyone knows an easy way to do this, I think the benefits would be doubled. Not only could I replace the existing output, but I could also use a pipe screen over the capsule instead of the little hole cut in the tin casing. This would probably improve high frequency response since I guess the hole is just a sort of low pass filter.

If I use the 5532, can i just hook up power, the compensation cap, and run the output to a 10k pot (with a coupling cap to block DC)? ...or do I need to build a circuit like the ones on the Jensen site?

Shane

You could do that, but you wouldn't get the best noise performance that way. (By the way, unlike the 5534, the 5532 doesn't use a compensation cap.)

It's better to vary the gain by varying the feedback resistor. Because there's going to be some DC offset across the feedback resistor it may be better to use a switched resistance than a pot, although I've used pots for this with no problems (yet).

If you are recording pretty much at the same levels all the time, like stealth-recording live bands, Kev's idea is the best. You probably don't need more than a gain of 3 to 4. A lot of stealth-recorders just take the output from Panasonics right into the line-in with no preamp.

What happened to this project?

it seems like a really interesting and usefull idea.

I starting to mess aroung with electret panasonic capsules also, and would like to build something similar.