Piezo contact microphone hi-Z amplifier – low noise version – Richard Mudhar
Contact microphone - Wikipedia
Piezo Contact Microphone Pickup for Guitar, Violin, Banjo, Mandolin, Ukulele: Amazon.de: Musical Instruments & DJ
Alomejor Clip On Kontakt Mikrofon Piezo Pickup, 3m 6,35 mm Audio-Piezo- Kontakt-Tonabnehmer für Akustikgitarren Violine : Amazon.de: Musikinstrumente & DJ-Equipment