Help with Cafewalter Buffer

[Jamforthelamb]

Hello Friends,

I built the cafewalter buffer here http://www.cafewalter.com/cafewalter/fetpre/index.htm to use in a cigar box guitar I've recently built with a piezo.
The buffer works great except that on hard attack it will clip. Any suggestions for circuit modifications to clean it up?
Thanks!
God bless,
Kevin

[earthtonesaudio]

Perhaps increase C1.  Piezos can put out very large transients; that's probably what's clipping the buffer.

Another really slick thing to do would be to put a couple of diodes on the other side of C1, reverse biased to the supplies.  That would shunt the excess energy of the transient to the rails, where it would add to the headroom of the buffer.  Kind of like bootstrapping in a way.

[Jamforthelamb]

Hello All,
Tried increasing the value of Cap 1 to 300 pf (2 more 100pf in parrallel) and I'm still getting clipping. Any more tips on how to clean up this circuit?

Thanks!
Kevin

[PRR]

Raise the battery voltage. Although any signal that clips that unity-gain buffer with a 9V batt is probably WAY too hot to go into a guitar-amp jack. (Indeed it may be your amp first stage clipping, not the buffer.)

Increase C1 _LOTS_. 1,000pFd. 10nFd.

If you need 10nFd to tame your piezo, then you may not need a buffer at ALL. Say 10nFd+3nFd= 13nFd total, against a typical 470K input, allows full bass to 27Hz, far below the range of guitar.