This is the diagram of a stethoscope published in EPE magazine May
2013.For a transducer, it uses a disk from a cheap piezo "buzzer" mounted in a diaphram type stethoscope head.
I ordered the PCB from EPE and built it up according to the instructions. But the gain appears to be insufficient, even with all the trimmers cranked up.
When the piezo disk is tapped, there is a sound. But no heartbeat when applied to the chest.
I have already tried piezo's from two different suppliers.
Can anyone please tell me how to make this work?
Mike Towner