This is small integrated amplifier at 20W using a TDA2004 or TDA2005 IC,use 12V supply for BCL car audio amps[...]
These are many pre tone control circuit, use transistors as main. so low noise,good sound, cheap and easy to buy parts, you can builds with PCB layouts
This is Simple preamplifier circuit using transistors,low noise and easy to builds we have many circuit below, simple to difference projects [...]
These are Tone control circuit using op amp - NE5532 or 4558 IC as low noise, with PCB layout, can adjust sound frequency and tone bass, treble, mid and..
This is a 4 transistor audio amplifier circuit. Which is a 4-transistors complementary push-pull amplifier, that shows the basics of audio amplifier design.