For many electronics enthusiasts who grew up in the post-Soviet space, V.G. Borisov’s book "Young Radio Amateur" is practically a sacred text. It’s where many soldered their first joints. I remember getting stuck on this circuit when I was 12. After a failed attempt to build a specific transistor amplifier from that book back then, I decided in 2016 that it was time to settle the score.

The result is a Class AB headphone amplifier built strictly on vintage Soviet germanium transistors. The circuit relies on MP37 and MP39 (МП37 / МП39) transistors for the driver stages, with hefty P213B (П213Б) transistors handling the output. Since original parts are getting scarce, I had to dig through donor boards to salvage the necessary germanium components.

It wasn't a plug-and-play affair. The initial build suffered from the dreaded "metallic" sound of crossover distortion. To fix this, the quiescent current was bumped from 10mA up to 50mA by tweaking the bias circuit with an additional diode, smoothing out the sine wave. I verified the result using an oscilloscope.

The stabilized power supply was also assembled based on an old 60's circuit using two germanium transistors. Unfortunately, I could not find germanium diodes or Zener diodes, so I used modern equivalents.

The build is housed in a custom "sandwich" style case made from 2mm acrylic sheets and brass standoffs, featuring under-body LED lighting that gives it a modern touch.

CAUTION! It is worth noting for the uninitiated: like many germanium designs of that era, this amp features a positive ground rail!

It’s a great example of how to revisit a childhood dream.