Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.
Sign up to join this community
I am attempting to design my own audio amplifier i have started the process with a block diagram. So far the "blocks" i have are:
Input audio signal → Band-pass filter → Preamplifier → Power amplifier → Load
The only restriction that has been imposed is:
Is a buffer amplifier needed between the input and band-pass filter?
The preamp would normally be the first stage, which is why it's called a preamplifier. It takes whatever the audio signal levels are (various line levels, mic level, etc) and normalises them. You put the equalisation and after that, and before the power amplifier (which has a high fixed current gain). Any level controls would normally be part of the preamp.
Basically, the preamp is the buffer.
Do you really need a band pass filter? What's it for?
Yes, the input resistor affects the band pass filter (or any other passive filter). So, you have three options:
You can use an active filter (where you should use an op amp or something like that). This active filter provide a very high impedance so you don't have to use a buffer between the input stage and the filter stage. Active filters also provide convenience gain control.
If you like to use a passive filter, you can use an opamp as a buffer between the input stage and the filter stage.
If you don't want to use an op amp or any active components, you should measure the resistance of the device that generates the audio signals (input resistance) and adjust the resistances of the filter to match your required cut of frequencies.
If you need a simple but powerful solution for audio amplification, I suggest using LM386 it is a power amplifier (not only a voltage amplifier) and it can provide gain up to 200. It is designed for audio applications. It is a very powerful IC, and easy to use and requires few components. It's just great.
