# What resistors and capacitors do on a audio circuit? [closed]

I'm a newbie, hobbyist, and i build guitar stompboxes fx using existing schematics. After building some of them i noticed they all use resistors, capacitors, and basic 3 pin transistors...

my question is: what they do? what's the principles behind it? can you suggest books, lectures or blogs where i can learn the basics so i can start playing myself maybe creating a circuit from scratch?

• Might be worth looking at a circuit, understanding what you can from jp314's answer, and asking some specific questions about the rest... at the moment it's a pretty broad question, a good University could answer it in three or four years <g> – Brian Drummond Dec 21 '15 at 17:08

Individual transistors are not very precise devices -- their parameters (e.g. gain) vary widely, and the operating voltage and current vary dramatically with temperature.

Conversely, resistors are reasonably accurate (say 5 %). They are used to bias the transistors (e.g. make the operation nearly independent of individual devices, temperature and supply voltage). They are also used to control negative feedback -- make the overall gain well controlled.

Capacitors are used to separate DC from AC signals -- basically bias from audio. They are also used to adjust the frequency response in case it is needed to compensate for imperfections in other devices (e.g. speakers). They are also used to filter noise (e.g. ripple from the supply), or act as small 'backups' for large surges of power.

They are like alphabets. A naive person will can't do much with it but a learned person can create a masterpiece out of it.

Similarly - Resistor controls the flow of current in the circuit. Capacitor can block DC and allow ac to pass through. A transistor can act as a switch or an amplifier.

However once you start combining these, you can make impressive circuits like delay circuit, op-amp, logic gates, constant current source, low pass filter, high pass filter, buffer etc. In fact transistor is the key component of all digital electronics that you see around. What you can do with these depends only on your knowledge and imagination.

If you want to start into electronics, I'd suggest "Practical Electronics for Inventors".