It was in the early 00's when we came across an electronic parts dealer who was selling - unknown to us at the time - parts from closed down former Soviet factories. Among them we found a huge range of Soviet tubes and also some very interesting resistors, capacitors and relays. The discovery of those unknown to us parts was a real challenge and we started testing them in various circuits. One of the tubes that stood out was the powerful and very robust 6c33. We found out, as did other experimenters, that this tube was excellent as an audio amplifier. Retron A1 amp is the result of many years of experimentation, circuit building, testing and listening. A single ended amplifier with high quality parts, hand-wound Retron transformers and excellent build quality that can excel reproducing any type of music and drive any load effortlessly.