Douk Audio. Any experience with any of their products?

Any experence with their passive pre?

I got the "6j1 Valve tube pre-amp preamplifier bass on music fidelity X10-D"
the ad exactly. For $13 bucks. It was an easy kit to build, tiny but I have to admit it held up.
I first put it in between a emotiva DAC and threadhold stasis amp. First my Maggie’s, wasn’t impressed. Laughed cause $12 I’m glad it made sound. But.. it started to warm up and sure I can hear that tube sound. Hooked up a pair of speakers with ribbons. It continued to open up. 
My preamp is a audible illusions modulus 1 tube and This little plastic pretty blue light toy sounded pretty good. damn well worth the $13 I spent. Perhaps,
Improving the cheap components like caps and resistors would make a serious difference. Tubes of course would make a serious deference.
The little engine that could. It's a fun hobby. 

Any particular tubes work with this size tube? These are smaller them 

Jaynewt- which seller did you buy your Dartzeel clone from? Prices are from 800 shipped to maybe $1600 shipped

thank you!!

@jaynewt I'd be interested to know too. Douk sell for $1600ish, but others sell for around 1/2 that. Are they the same clones?

Ref . Douk audio and Amy . I have purchased the Hi-Fi 2.0 Channel Stereo Amp Board Kit/Set_UK and it was the biggest mistake I have ever made. Before I started the build I checked the contents and found that a number of components were missing so I made contact with Douk through Ebay and received a prompt reply from Amy saying would I purchase the missing parts in my country and they would pay .From that I assumed the reply was coming from China even though it was supplied from UK stock , I replied that I was not in a position to do that and if they could not supply the missing items I would complain to Ebay through the appropiate channels . I received a quick reply as follows.... hello dear customer wish you a very nice day OK will resend it the tracking number is JV093944637GB best regards Doukaudio-Amy")..... What they are sending I have no idea.  I am no pro. at building circuit boards and at the age of 91 I thought it would give me an interest having built a number of Heathkit items in the past but I am now in trouble reading the resister coding as no instructions are provided in the kit , just a bag of bits and two heat sinks , HELP. Albert Bennett.