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. DescriptionR1 1 10K 1/4W Resistor
R2 1 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 2.2K to 10K Audio Taper Pot
R12 1 330K 1/4W Resistor
R13, R15, R16 3 1K 1/4W Resistor
R14 1 3.9 Ohm 1/4W Resistor
C1, C8 2 470uF 16V Electrolytic Capacitor
C2 1 4.7uF 16V Electrolytic Capacitor
C3, C4 2 0.047uF 50V Metalized Plastic Film Capacitor
C5 1 0.1uF 50V Ceramic Disc Capacitor
C6, C7 2 1000uF 16V Electrolytic Capacitor
U1 1 TL072 Low Noise Dual Op-Amp
U4 1 741 Op-Amp
U5 1 LM386 Audio Power Amp
MIC 1 Two Wire Electret Microphone
J1 1 1/8″ Stereo Headphone Jack
Batt1, Batt2 2 9V Alkaline Battery
LED 1 Red/Green Dual Colour Two Wire LED
SW 1 DPST Switch
MISC 1 Stethoscope head or jar lid, rubber sleeve for microphone, board, wire, battery clips, knob for R11
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