Listening device

[habbott]

Hi, I found this circuit on this site and would like to know if this would be suitable for a listening device for using around the automotive area. Instead of using a speaker I would like to use headphones would I need to change any components for this to work.

 

[HiTech]

Here's a better one that employs a low pass filter to reduce background noise.
CIRCUIT #1

Here's a similar one submitted by none other than our own prestigous member, Audioguru:
CIRCUIT #2

 

[habbott]

Thanks

Which one in your opinion is the better circuit. What is a stethoscope head could I make this. Is it just a sleeve the houses the mic.

 

[audioguru]

The bare-bones LM386 amp circuit will pickup all kinds of background noise but is simple.
The project from Aaron Cake has errors so doesn't work.
My Electronic Stethoscope-2 project fixes the errors in Aaron's circuit and works fine.

 

[habbott]

Capacitors

I am looking at building the Electronic Stethoscopes 2 by Audioguru. How important is the voltage rating of the capactors is it ok to have a large voltage capactor as I have most of what is required but the voltage is higher like 63V or 100V. What is a Metalized plastic-film Cap is this a MKT or Green cap.

 

[audioguru]

I am looking at building the Electronic Stethoscopes 2 by Audioguru.

Maybe you haven't seen the complete project:
https://www.electronics-lab.com/projects/science/019/index.html

How important is the voltage rating of the capactors is it ok to have a large voltage capactor as I have most of what is required but the voltage is higher like 63V or 100V.

High voltage electrolytic caps are huge and expensive. 16V ones are fine for the 9V supply circuit. High voltage ones will also be fine.

What is a Metalized plastic-film Cap is this a MKT or Green cap.

I use 5% tolerance MTK but the Oriental "green cap" is about the same. Some people call them "mylar" or "polyester" caps.