Electronic Stethoscope

Electronic Stethoscope
Source: http://www.aaroncake.net/
Stethoscopes are not only useful for doctors, but home mechanics, exterminators, spying and any number of other uses. Standard stethoscopes provide no amplification which limits their use. This circuit uses op-amps to greatly amplify a standard stethoscope, and includes a low pass filter to remove background noise.

Part
Total Qty.
Description
Substitutions

R1
1
10K 1/4W Resistor


R2, R3, R9
3
2.2K 1/4W Resistor


R4
1
47K 1/4W Resistor


R5, R6, R7
3
33K 1/4W Resistor


R8
1
56K 1/4W Resistor


R10
1
4.7K 1/4W Resistor


R11
1
2.5K Pot


R12
1
330K 1/4W Resistor


R13
1
1K 1/4W Resistor


R14
1
3.9 Ohm 1/4W Resistor


C1
1
470uF Electrolytic Capacitor


C2, C3, C4
3
0.047uF Capacitor


C5
1
0.1uF Capacitor


C6
1
1000uF Electrolytic Capacitor


D1
1
Bi-Colour LED


U1, U2, U3, U4, U5
5
741 Op-Amp


MIC1
1
Electret Mic


J1
1
1/4" Phone Jack


MISC
1
Board, Wire, Sockets for ICs, Knob for pot, Stethoscope, Rubber tube

Notes:
1. MIC1 is an assembly made out of a stethoscope head and electret mic. Cut the head off the stethoscope and use a small piece of rubber tube to join the nipple on the head to the mic.
2. Be careful with the volume, as excess noise level may damage your ears.
3. The + and - 9V may be supplied by two 9V batteries wired in series and tapped at the junction.
4. R11 is the volume control.