My brother and I have build two 6C33 SET (single ended triode) 15 Watt Class A amplifier. This is a very nice amplifier with a very pleasant warm soft sound and you don't get tired listening to the amplifier and ee are very pleased with the finished result.
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The finished amplifier. We both choose a beeswax oak wood frame as the enclosure, a bit expensive, but we are very pleased with the results. We have thermometer on the PIC pcb and the maximum temperature inside the case is approx. 52°C, so this is a hot amplifier.