2A3 SE

What topology to use is a matter of requirements for the outcome, finish and way, method or ease of construction. I used to go for push-pull to get more power, but today I am into single ended designs as they are easier to build and require less components.

This is to describe a project I have dreamt about for a long time - a DHT amplifier. I figured that 300B was a bit expensive, an 811 or 211 or GM70 required to much volts. A 2A3 was maybe the most perfect choise for an "experiment", especially as the tubes were offered at a very attractive price.

I picked a simple design for the amplifier using a 5842 as driver and cheap Valve Art 2A3 together with a Russian 5AR4 as a rectifier.
Paid some attention to chassis, wondering if a wooden top would be nice, but dropped that idea and went for a brass top mated with a wooden frame.

I made some mistakes like missing a way to supply 5V for the rectifier and a sound way to balance the 2A3's. I think I also made some mistakes by trying to make a nice arrangement knobs for mains switch and volume potentiometer. Thinks I have to look deeper into.

When picking passive components I am go for cost/quality. No fancy overpriced crap here because a Golden Ear has said that tantal resistors sound better. The potentiometers are for balancing the heaters - 2W, cheap from German (Swedish) Conrad.
When I start again, I have to redesign some parts, but those are mainly cosmetical.

SCHEMATICS

The second design is a Loftin/White, a design I picked first and even have the big

 

PHOTOS