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!

 

[TamTannoy]

Hi everyone, this is my first post.

Last week I have built this amp. I have learned a lot from it. I can solder, repair and recap but this was my first time building an amplifier.

In order to make sure I used solid components for maximum results, I ditched the capacitors that came with the kit. The MKP10 ones were fakes and the other caps had very high ESR. I replaced them with real Wimas (twice the size) and 105oC Panasonic and Multicomp caps of the same value. The resistors measured perfect so I used those.
Also I chose different tubes. The old ones worked fine but I used NOS Voskhod 6N2-PEV and 6P1P-EV.
The stock side panels looked rather cheap so chose merbau hardwood.

Mistakes I had to redo during this journey were making sure I had one star ground instead of attaching the ground of the RCA to the chassis and placing the Wimas too close to the power lines. At first I encountered oscilation and echo form both speakers. Which were gone after the alterations.

On YouTube I found a guy who had video documented the exact build very extensively and he had a very useful overview picture which was much better than the Chinese schematics.

I am very pleased with the end result. Although it is still breaking in, the sound is above what I expected for the money! It's not the most refined amp I have ever had (probably because of the cheap transformers), but the soundstage is huge pretty damn tubey. I have it hooked up to a pair of Tannoy DMT15 MK2.

I paid $70 for the initial kit on aliexpress, 60 for shipping to the Netherlands (which took about three weeks), 20 for the new caps and 30 for the new tubes, and I have spent 10 for the cage which I fabricated from an Ikea bathroom basket.

All in all I enjoyed this adventure a lot!