Piezo Element Amplifier for Guitar and Violin

Rajkumar Sharma
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SKU: EL122204
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The board presented here is a preamplifier for contact microphones that are used for amplifying the sound of musical instruments which do not contain electrical pickups, such as guitar and violins. Most contact microphones use a piezo element to convert vibration in the body of the musical instrument to a voltage. The circuit is built using OPA1678 OPAMP. The low noise and low input bias current of the OPA1678 makes the device an excellent choice for high impedance preamplifiers for piezo elements. This preamplifier circuit provides high input impedance for the piezo element but has low output impedance for driving long cable runs. It provides a balanced audio output that can be fed to a balanced microphone pre-amplifier. The circuit has also the option for phantom power input. Install R3=1.2K Ohms, R2=1.2K Ohm and Zener diode 24V.

Note: The project can be interfaced with “Phantom Powered Microphone Pre-Amplifier using SSM2019” published on our website.

Features

Supply 24V DC @ 5mA
–3-dB Bandwidth: 20 Hz to 20 kHz
Gain: 20 dB (10 V/V)
Balanced Output
Screw Terminal for Output Connection
Screw Terminal for Piezo Element Connection
Male Header Connector for Supply Input
Optional Phantom Power Input
PCB Dimensions 56.20 x 22.54 mm

Schematic

Parts List

NO.	QNTY.	REF.	DESC	MANUFACTURER	SUPPLIER	PART NO
1	1	CN1	4 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5317-ND
2	1	CN2	3 PIN SCREW TERMINAL PITCH 5.08MM	PHOENIX	DIGIKEY	277-1248-ND
3	1	C1	100uF/35V	RUBYCON	DIGIKEY	1189-2268-ND
4	1	C2	0.1uf/50V SMD SIZE 0805	MUARATA/YAGEO	DIGIKEY
5	2	C3,C6	22uF/50V	NICHICON	DIGIKEY	493-10491-1-ND
6	2	C4,C5	390PF/50V SMD SIZE 0805	MUARATA/YAGEO	DIGIKEY
7	3	D1,R2,R3	DNP
8	1	D2	DIODE TVS TPD1E1B04	TI	DIGIKEY	296-46892-2-ND
9	1	PT1	2PIN SCREW TERMINAL PITCH 5.08MM PIEZO DISC	PHOENIX	DIGIKEY	277-1247-ND
10	4	R1,R5,R14,R15	100E 5% SMD SIZE 0805	MUARATA/YAGEO	DIGIKEY
11	2	R4,R13	1M 5% SMD SIZE 0805	MUARATA/YAGEO	DIGIKEY
12	4	R6,R7,R10,R12	100K 5% SMD SIZE 0805	MUARATA/YAGEO	DIGIKEY
13	2	R8,R11	2K 1% SMD SIZE 0805	MUARATA/YAGEO	DIGIKEY
14	1	R9	442E 1% SMD SIZE 0805	MUARATA/YAGEO	DIGIKEY
15	1	U1	OPA1678 SOIC8	TI	DIGIKEY	296-47347-1-ND