Preamp Schematic I Found On The Web. Feed Back Wanted.

[LJOE1969]

Hi.

I found this on the internet and i want some feedback.

will it work?
what characteristics will it have? etc...

[Optical]

That is teh simpliest of opamp circuits, it is more or less a volume control

[darkfenriz]

if it is for guitar then input Z (of 110k) seems low

[Giaime]

Mmmm.... bad things. The circuit would work, but with low input impedance (guitar or bass needs 1Mohm) and opamps which is good to avoid and just use a single FET.

See here:

http://www.till.com/articles/GuitarPreamp/

[DrDiode]

Well after a few mis conceptions of the circuit...

This circuit will work but in my book that op-amp is a bit noisy

The input Z isnt what they say it is...and really the hum buckers are lower Z that lots of the "Experts" say anyway.

Single coil pickups arent that high either. But all in all we are looking to "Squeeze" every mV of signal out of the poor guitar electrical system so if you are that worried about it.. Create a buffer that allows the proverbial 1/2meg input and drive the stuff after. that with a lo Z feed

The FET preamp that Tillman designed helps in that it changes a hi-Z to a low and gives some gain.By-pass the Source resistor and see what it does..**Smirk** and stand back. he forgot to tell you it has more gain than stated if you want it.

...also there's a decoupling trick that RF guys use.(I'm one of them)
put a low value resistance (100 ohms is a good starting point) Connect it to Vcc.

The other end bypass it well .. with like a 100uF cap to ground and maybe a .1uF also..

Connect the drain resistor to that instead of to the supply rail.
You will lose some noise present.something we all strive for.

This is a typical trick in high end test equipment / RF stuff and just as real for audio.

[thedoctor]

That Tillman preamp design shows all of the benefits an fet has over an op-amp. It can also be made as small as a dime for use in a guitar control cavity. Paul Morrosey even has made cble ends with the pre powered by phantom votlage. When you use a 9-volt battery, expect it to get VERY grumpy when the voltage drops below about 7.5.