Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
R8 allows C5 to be a much better filter. The circuit might "motorboat" if R8 is removed and the battery is not brand new (its internal resistance is high).
I simulated the Talking Electronics spy amplifier:
1) Its high frequency response cuts frequencies above 300Hz. At 3kHz the response is -28dB down.
2) Its distortion is extremely high.
3) Its gain is very low.
4) Its output level drops with elasped time.
I corrected the value of the biasing resistor for the output transistors and made it work much better.
Now the capacitors that cut all the mid and high audio frequencies should be removed.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.