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Emad

Electronic Stethoscope 2

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Hi Greg,
Mylar is a plastic film. Capacitors are made from it when they metalize one side of it.
An oriental "green cap" is also a metalized plastic-film capacitor and I have seen orangish-brown ones. 0.047uF is marked "473". 5% tolerance is marked "J". So you need capacitors marked "473J".

Hi Dhyne,
Last year, Con posted this good pcb layout:

post-1706-14279143543232_thumb.jpg

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Thanks for the info, Hero.

Sorry, i've got a couple of questions to ask.

Is this the right way to wire the stereo headphone? (Kindly see attachment)

Secondly, there is whining sound when i am using a headphone (with and without the mic attached). When i touched or moved my hand near the potentiometer, the whining sound became softer or disappeared.  Any idea what is the cause for it? (I am testing it on a breadboard)

Thanks, sparky

post-45548-14279143889335_thumb.jpg

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Is this the right way to wire the stereo headphone? (Kindly see attachment)

Yes.
Short the left and right channels together so both ears play in mono.

Secondly, there is whining sound when i am using a headphone (with and without the mic attached). When i touched or moved my hand near the potentiometer, the whining sound became softer or disappeared.  Any idea what is the cause for it? (I am testing it on a breadboard)

The long jumper wires of a breadboard pickup all kinds of interference and might cause the circuit to oscillate.
Use a compact stripboard layout or a compact pcb layout instead.

Thanks, sparky

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