UX-171A Tube Amplifier

This amplifier uses the UX-171-A tube (matched pairs) which are rare and produce only 1/2 W of output power. There are no resistors or capacitors in the audio circuit. A Hammond 124B nickel core inter-stage transformer couples to the power tube. Edcor 10W OPTs in the metal case. Bias is provided by 3 x 9V batteries and 230V by two step-down transformers wired in reverse. The rectifier tube is a very old "80". Power supply filtering is under the top plate (ply timber). The base houses the power transformers and is a 1940s wooden pot stand. The tube amplifier sounds excellent.

For more info, see the 171-A single-ended amplifier thread in the forum.

Mark Houston – retro-thermionic