A world class reproduction sound system with just a few components

At your risk. All safety precautions should be followed with any voltage or current.


A fuse should be always be connected in series with a battery.


All needed is:


A good source of music signal. It may be a Walkman CD player.


One BD139 transistor


A heat sink


The Pleiades BD139 one transistor schematic


One bias resistor


A 12V battery in series with fuse


A potentiometer for volume control in series with base circuit.


A big, heavy output transformer of primary inductance say 100mH and secondary inductance 25mH. 25mH works well for a 12Ω speaker. For a lower impedance speaker a correspondingly lower secondary inductance should be used.


A world class baffle sensitive fullrange speaker.





Even an operating point of 10V 50mA will sound loud, amazing, broadband, natural, dynamic, big.


This is just a power dissipation of 1/2 watt. Mighty power output should be about 250mW sending to the cleaners almost any amplifier regardless of power output.


Such loudness can be achieved that one has to move to another room when for example a sax (Carlos Jobim albums) is playing loud similarly to having a real saxophone playing in a small room.


A Zeiss Ikon typ:31-06 baffle speaker is used.


See also:
https://euroelectron.blogspot.com/2019/05/zeis-ikon-typ31-06-baffle-fullrange.html