[gb243]

The Douk kit utilising  5Z4P, 6N1 and 6P3P tubes appears to have an error in the PSU.

The 47uF reservoir capacitor from the 5Z4P rectifier appears to be up to 3 times the maximum value it should be. The datasheets for the 5Z4G tube, depending on the manufacturer give a max of either 32uF or 16uF. Best to be safe at 16uF. I had a 5Z4P tube burnout on me, and the replacement started doing the same before I checked the datasheets. The Chinese datasheet, as far as I can check, does not seem to give a max cap value. The 5Z4G is supposed to be equivalent so  I would say it is worth replacing the reservoir cap if you have already built this amp or plan to do so.

Also my 6P3P tubes were dreadful (buzzing, pops and bangs) and I replaced them with 6L6Gs. Now it sounds pretty good.

[raindance]

The 5Z4P is a kenotron, copied from a Russian tube and even though the data shows a very small cap, should be happy up to 50uF. The things to watch in this amp are mains voltage (transformer is 110 volts input, at my house I get 125 volts and use an APC step down device to get 110 volts) and the way the tubes are strapped for pentode operation without a limiting resistor. I have an improved schematic somewhere, I'll see if I can find it. I modified mine so I can run EL34 tubes, but oddly, I preferred the 6P3P.

By the way, I only get about 3 watts per side out of this amp. The power transformer runs hot enough to cook eggs on even at 110 volts.

[FullRangeMan]

The power transformer runs hot enough to cook eggs on even at 110 volts.

This trafo could be 100V for japanese market or the primary is too small?

[raindance]

The transformer is under-rated. It is designed for 110 volts. I'd suggest never leaving it unattended when it is on