Re: Roland PK-5, Ketron 9PEMK8, or else? (piezo impedance)

[Matthias Grob <matilists@gmail.com>]

the preamp is not for the volume but the linearity of the sound

while the magnetic pickup are coils that have a high impedance in high frequencies

the piezo is a capacitor and such has a high impedance in low frequencies

so if you connect a magnetic pickup directly to a mic input (low impedance) it sounds dull because the high frequencies get lost and a piezo sound thin because the bass is lost

if you connect a piezo to a high impedance (guitar) input, its ok. depends on the size of the piezo as well, smaller ones rather need higher impedance 

On 18 Jul 2012, at 5:37 PM, bill bigrig wrote:

Don't forget, these peizo units work wonderfully on violins,(fiddles), mandolins, violin-ukes, all sorts of metal clanky devices, and on and on. They do not work real well on acoustic guitars because of the difficulty of taping it on the instrument where it does not sound, "boxy". At $2.79 each, they are a good value. Be careful not to disturb the solder connection on the disk itself. Cut off and discard the blue wire. You will see the obvious center connection, and the outer, "shield" connection. I've been using them for 30 years now, and despite some claims that a preamp is essential, (I think it comes from a prominent peizo based pickup manufacturer), if you have an input gain control such as that on a mixing board, you will find more than enough output to do the job.
Rig