Frog Jfet Buffer/Preamp - onboard guitar?

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Frog Jfet Buffer/Preamp - onboard guitar?

Postby mark.price » 04 Aug 2016, 17:04

From the home of the Frog Tube Preamp PCB comes now, the Frog Jfet Buffer/Preamp PCB:
I just sent my second prototype version of the "Tillman" JFet preamp to fabrication. Within a few weeks I should have it back and tested. Assuming that will go well, I will then send out to production fabrication (in higher quantities) and sell on (where I am currently selling my Frog Tube Preamp PCB). As a reminder, the reason I designed this PCB is so I could mount the buffer/preamp in the body of a guitar I am building. I call it the Cubist guitar (see pics). Anyway, my intention is to have magnetic and piezo pickups in the guitar and needed a buffer/preamp for the piezo pickup portion. What I have found is that you can use this buffer/preamp for magnetic or piezo pickups with just a change of a resistor in the input. For piezo, you use a 2 megaohm to 10 megaohm resistor on the input. For magnetic pickups you use the standard 1 megaohm on the input. I will use two in my guitar and use a 9 volt battery onboard the guitar, switched via the 1/4 inch jack. All reports indicate that if you use a J201 jfet, you can run hundreds of hours. I have not tested the longevity of a battery myself. There is a switchable boost option which uses a capacitor that bypasses the source resistor and man does it boost! In the attached pictures, you will see the small size of the first prototype PCB. The second prototype is marginally larger, still around 1 x 1 inch (25mmx25mm). I plan on mounting the finished prototype you see in a 1590A type enclosure. You could probably mount in a 1590G too! ( I may fit two in series and see what it does for boost/overdrive? just thinking outloud!)
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