Hi Michael, last thing it's going to be it "the piezo". ..and unlikely the the circuitry connecting the piezo to the o/p of the guitar is creating a whine.The sound is more typical of those that are produced by a laptop/soundcard combination that isn't well earthed for audio.
With the ultimate culprit being the laptop power supply.Rusty's solution sounds good. & +1 for Dennis
Other things to try1) change the whole jack cable 2) run laptop on batteries (most common fix for that noise) 3) change technician ;-)
Other wise not possible to troubleshoot at a distance without knowing the setup. Need to know how the audio interface is powered. andy Michael Peters wrote:
http://www.michaelpeters.de/temp/soloette-hum_0001_0.wav When I plug my Graduette Soloette guitar (a nylon string travel guitar with a piezo pick) into the external soundcard of the laptop and launch Bidule to hear it, I find that it hums - a deep drone hum plus a high whining sound. This does not happen with regular electric guitars. My technician says it has to do with the piezo. When I put a finger on the jack cable that sits inthe connector in the guitar, the noise stops.I can get rid of the deep hum with a plugin, but the high whining noise is still there. I can't play with my finger on the jack cable all the time. Is there a simple way to get rid of that noise? a special VST plugin? or some kind of grounding cable that I connect to the plug? and where does the other end go? I need a quick and simple solution. Help! -Michael