I was looking for a simple onboard preamp or buffer to hook up with a piezo under-saddle transducer. How would R.G.'s onboard buffer (http://www.geofex.com/FX_images/Onboard_Preamp.pdf) suit? I really like the simplicity (and it's all I need), but I've not been able to find any mention of it being used with piezos. Would the input impedance be high enough? If not, could it be tweaked easily?
Seems like it could be tweaked easily enough. I plan on breadboarding this over the weekend (read "sometime in the next 6 months when I have free time") and playing with it to find the ideal sound for my electric, then I was thinking about trying it with the acoustic as well. If nobody gets to it before me I will let you know how it goes :P
> Would the input impedance be high enough?
Yes.
Thanks Paul.
If you want something even simpler, a JFET buffer works pretty well. I replaced the onboard preamp in a friend's Epi acoustic and we both liked it better, except there was no quick way to adjust the tone/eq/volume as before.
http://personalpages.tds.net/~fdeck/bass/quickand.pdf
LOVE this one... it was the first active circuit i ever built, and i have built and used several of them. 2n5486 is my favorite choice.. you can fit this anywhere
+1 for Deck's quick-and-dirty buffer. If you want to keep the low-end response decent even on a guitar, you'll need to get close to that 10Meg input impedance. For example, even with 1Meg input impedance your low-end will be clearly dampened. A FET buffer is suitable, because its intrinsic input impedance is more like 100Meg, so all you need to do is to select the gate-to-ground resistor to fix your input impedance.
Thanks for these suggestions too. I've also found the piezo article (http://www.muzique.com/news/piezo-pickups/) on Jack's blog, which looks interesting.
Edit: added URL to Jack's blog.