would jack ormans mosfet boost make a good mic pre...?

if so, how would i convert it over to adequately recieve
mic signals....any impedance issues to worry about?

It works as a 'clean' boost if there ever was sucha thing.
 Has alot of gain..I forget, but it's listed in the AMZ article.
 Very low distortion. I tried as a MIC booster, but into soundcard I found there was no real tangible benefit...Mic itself gets the meters going.
 If you're having troubles getting sufficient output to a power amp or such, I'ts worth a try.
 Generally a mixing board has enough line output to drive most amps.
 I believe the impedance characteristics of the Booster are 'nice' to work with...can't really say beyond 'should be fine', depending on what I'ts hooked to.
 Anyway, this is a great circuit to have in a box.

hey pete...

yup, i have a hard disk recorder that has no mic pres to speak
of and so i figured that if i could come up with a simple
and inexpensive 8 channel mic pre, that would be super cool....

just a thought.

Well this throws *inexpensive* out the window, but you may want to check it out:

http://www.hamptone.com/newkits.htm

 An article with the schematic ran in TapeOp a while back.

The TapeOp forum might be a good place to get some ideas also.


Kerry M

Yeah, i actually have that issue of tape op.   good stuff indeed.
hamptone has always had very good quality stuff.
interesting too.

i have some presonus gear and some other mic pre's, but would
like to diy a simple mic pre, and this one looked pretty simple....
i just wanted to know if i would have any impedance issues
using an xlr for the input rather than a 1/4"....
supposedly this booster (orman's) is very transparent.....

thanks for any help...

Yes and no.

It's clean, full bandwidth, and has a nice high input impedance.  On the other hand, mics have a considerably lower output impedance than guitars so the 10meg input of the AMZ booster is overkill.  As well, mics have a much lower output level than guitars, so the amount of boost it provides is generally not in the same league as what "real" mic preamps provide to bring a mic up to line level for samplers, etc.  

On the other hand, if your goal is to plug a voice mic into the other input of your amp, this'll do just fine.

o.k.  i got ya....

i really like the simplicity of that circuit for a mic pre.

is there anthing similar you could point me to do an adequate job?

or any modifications on this circuit....can the gain be increased
to be up to snuff?

Amz Article Mosfet Boost has info on changing the input impedance, basically like Mark said, drop the R value of the huge 10m resistors....I forget how low you can go.

thanks pete....

im going to just have to try this thing out....

if all else fails, ive got a nice boost for guitar.