Stream 3 signals from Piezo sensors through USB to my PC

[alonper]

Hi,

for a research I'm doing I need to stream 3 piezo sensors that attached to an acoustic guitar to the PC through the USB interface...
So I need to design and build configurable Preamp for Piezo Sensors (It will be used with a various of woods-->result different impedance of the piezos), ADC and sone USB gate to react at sound card..
any suggestions?
currently I am trying to work with Teensy and their Audio Board (with SGTL5000 codec) but its problematic since it react only as stereo channel USB sound card...and I tried to design by myself a preamp for the piezos but It works pretty bad, since I dont have deep knowledge with analog..
So I will be glad to get recommendations or links to :
1: USB processor\gate to stream 3-4 signals..
2: 4\2 channel ADC
3: Schematic for a piezo pickup (super high impedance..)

attached the current schematic that I have for the pre-amp part..If you can, please give me advice how to make it better.
I am using the MCP6021\4  http://ww1.microchip.com/downloads/en/DeviceDoc/20001685E.pdf as the opamp - and I have only 5V single power supply


Thanks in advance for any help
I'm struggling with this project for about one year already and I'm going to give up..
Alon

[markseel]

Here's a usb audio interface (up to 32 channels).
http://www.diystompboxes.com/smfforum/index.php?topic=114354.msg1112245#msg1112245

Add two audio ADC's (like the AK5386) for four channels of analog input with 3 of 4 of those inputs connected to your piezo signal conditioning circuits.