Audio preamp circuits

Here is another mini circuit project. You can comment here if get something wrong with this electronic schematic design

A high gain transistor like the MPSA-18 for the first transistor will allow a much larger value for R, up to 1 Megohm. The circuit should draw between 18 and 45 mA, a value determined by the transistor gain and the value of R.

Here is a phase-shift audio oscillator with excellent distortion characteristics thanks to “softened” diode limiting provided by the 1N914 and resistor divider and degenerated gain provided by the 68 ohm emitter resistor.

The TL431 is available in a TO-92 package and it looks like an ordinary transistor so your hobbyist friends will be impressed by the volume you are getting with only one transistor and the amplifier may be used for other projects, too.