Just for fun: $160 Douk 6N2 + 6P1 tube amplifier kit

[JeffS7444]

Alright, nearly a year since my initial post, my leisurely (or just plain slow?) build is complete!

Prior experience with inexpensive tube amplifiers was that out-of-box performance was typically kinda uncouth, and that's what I'm seeing here with an ultrasonic frequency response peak causing overshoot in this square wave. In anticipation of this very thing, I left room for low-pass filtering at the input, and if needed, frequency compensation capacitors in the feedback loop.

 

[JeffS7444]

Sounds pretty decent nevertheless.

From brown turret board to input tube are a pair of 10K ohm grid stoppers. Small perf board with large diodes was inspired by Pete Millett's ground loop breaker, and it's the only point of contact between signal ground and Earth. Objects covered in red heatshrink tube are simple pin header + pin allowing me to switch feedback loop from 8-ohm to 4-ohm taps as needed.

Green/yellow transformer wire isn't documented in this kit, but is mentioned in other Douk kit descriptions. It apparently connects to a shield, and should be connected to signal ground. Although it looks a bit alarming as it emerges from the primary side of the transformer, it's not connected to any of the high voltage windings.

 

[JeffS7444]

A little mod to the input to tame that high-frequency bump in the amplifier's frequency response.

And now I get a much better-looking 1 kHz square wave.

 

[Somafunk]

A damn site more interesting and useful than those weirdo’s with their penchant for building Lego models

 

[mhardy6647]

A damn site more interesting and useful than those weirdo’s with their penchant for building Lego models

hey!