Maker Pro
Maker Pro

I need a low-noise guitar pick-up preamp...

P

Phil Allison

Jan 1, 1970
0
"Ken Smith"
Ok, bootstrap the bias then.



** Bootstrapping increases the impedance as seen by the source, but does
nothing for the noise contribution of the resistors - in fact it increases
it.

Just up the bias resistor values to say 2.2 Mohm - the FET will not
care.



......... Phil
 
E

Eeyore

Jan 1, 1970
0
Phil said:
"Ken Smith"


** Bootstrapping increases the impedance as seen by the source, but does
nothing for the noise contribution of the resistors - in fact it increases
it.

Just up the bias resistor values to say 2.2 Mohm - the FET will not
care.

Agreed.

Graham
 
What's the problem with 9V (6F22) batteries? Why use AA cells? Tell
me.
I will probably need two 9V batteries since I don't like using single
ended supplies,
and I will need higher supply to have a decent output level and
headroom.

Also, how could anyone say "don't like to sound of op-amps". It all is
up to how to op-amp is wired up.

For the moment, I think a TL072/TL074 will do just fine, I'm a little
afraid of it's noiselevel though.
Besides, going for a NE5532 will make the batteries last much less.

Regards
PAF

I have this 9V jihad. It is the most expensive battery for the power
you get out of it AA cells are the best bang for the buck.

Before you get too concerned with signal swing, you need to determine
what voltage will clip the amplifier downstream. No use driving it
deeper than need be into clipping.

You realize the sensor (pickup) isn't going to be noise free. Thus
there are diminishing returns in making the electronics very low
noise. The deal with analog design is to select the right engineering
compromises.
 
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