I had two BD250C and two 2SA1490 PNP transistors that i dident have the NPN complement for, so i decided to make a small low power class A amplifier with them.
the BD250C's were put to use for the constant current sources and the 2SA1490's became the audio handler.
A few minutes in LTspice produced this circuit: http://i.imgur.com/T61DD.png
The idling current was set to 2.5A for up to around 5 watts into 4 ohms at a PSU voltage of 16 volts.
The psu is one 2x12V(secondaries in parallel) 80VA transformer for each channel, at the time beeing, the two transformers are wired in parallel as i used them to power a wordless drill.
A picture of the actual amplifier: http://i.imgur.com/YHfHk.jpg
Simulation shows between 0.1 and 0.3% THD near full power at 20kHz and the sound is really good, especially when the source is vintage vinyl records, but the amp also have the grunt to reproduce the music of today.
Today is day 2-3 the amp is running so i deem it stable, the heatsinks stabilize around 80 deg C judging from feel, can touch for about 3 seconds, and thats just sitting on the table with limited convection.
the BD250C's were put to use for the constant current sources and the 2SA1490's became the audio handler.
A few minutes in LTspice produced this circuit: http://i.imgur.com/T61DD.png
The idling current was set to 2.5A for up to around 5 watts into 4 ohms at a PSU voltage of 16 volts.
The psu is one 2x12V(secondaries in parallel) 80VA transformer for each channel, at the time beeing, the two transformers are wired in parallel as i used them to power a wordless drill.
A picture of the actual amplifier: http://i.imgur.com/YHfHk.jpg
Simulation shows between 0.1 and 0.3% THD near full power at 20kHz and the sound is really good, especially when the source is vintage vinyl records, but the amp also have the grunt to reproduce the music of today.
Today is day 2-3 the amp is running so i deem it stable, the heatsinks stabilize around 80 deg C judging from feel, can touch for about 3 seconds, and thats just sitting on the table with limited convection.