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Author Topic: preamp for K&K  (Read 2299 times)

Buffalo Sam

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preamp for K&K
« on: November 20, 2013, 04:27:54 PM »
I just had a K&K pickup installed in an acoustic guitar and it turns out I need a preamp that is impedance matched for the pickup.  My understanding is that means K&K, Ultrasound, or maybe Redeye.  Any others I should consider?

Roly

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Re: preamp for K&K
« Reply #1 on: November 21, 2013, 10:01:05 AM »
Acoustic guitars get fitted with piezo pickups which are vibration-sensitive, however the native pickup element is very high impedance and therefore very sensitive to amp load resistance and cable shunt capacitance causing serious low and high frequency losses, so these days a buffer/control box/battery holder is often fitted into the side of the guitar.  While these can all sorts of fancy controls, some even useful at times, a single FET will fill the basic needs. 

Don Tillman's FET Preamp Cable
http://www.till.com/articles/PreampCable/
This would be an ideal circuit, but it could be built in other ways, such as into a beltpack, or inside the guitar itself with a battery.

AMZ JFET Buffer
http://www.muzique.com/schem/eagle.htm
I'd lift R2 and R3 to 5.6 megohms for your application

The Mint-box Piezo Buffer
http://www.scotthelmke.com/Mint-box-buffer.html

Assuming the guitar is fitted with a socket (and if not there is a very neat tail-strap-knob-and-socket combination available) then a short run of low capacitance cable back to a beltpack with battery and preamp.  (and naturally you'd like some volume and EQ controls on that  ;) )
If you say theory and practice don't agree you haven't applied enough theory.