DTQWT built by HUH/Thailand

First of all I like to thank you for sharing your views, experience and findings on your excellent website. This truly has been an eye opener and inspiration for me.
Planning for, and building the DTQWT has been great fun, and I am pleased with the results . I completed the project about two weeks ago, and the speakers are now breaking in - so far so good.
Unfortunately one of the 10" Pioneer bass drivers ordered from Parts Express arrived damaged, and could not be used. I tried to order a new one from Parts Express, however the item is now out of stock, and when I called them they told me, that they are not planning to re-stock. Apparently the manufacturer has stopped producing this particular model. I thought I just drop you this note, since you might want to know ... If you by any chance do know about an alternative supplier, who still could have stock - I would be extremely grateful for a short note.

DTQWT - Some initial observations: For the past 3 years I have used a pair of Klipsch rf-25 speakers, which were easy to drive for my 300b and 845 amplifier, and which to my ears sound good, and fit for purpose. The only problem was a slightly muddled/boomy bass, and the speaker being on the bright (sharp) side of things. I was eager to see, whether for my particular setup the DTQWT could have some answers, and with the good help of my friend Khun Kasem (who was an enormous help re cabinet construction) I embarked on this project. But also - it looked like a "real fun" project ...
So far the result has been very encouraging. Although obviously one driver is missing, bass performs tight, and as you describe it "dry". The speaker is very revealing and all details are there ( without ever screaming) I traded soundstage against imaging, by toeing the speakers slightly inwards. In my room this works well.

By mid 2007 I placed an offer on Ebay for a Chinese Amp called " Mr Liang LS-845-3. My bid was very low, and I did not expect to win the auction. I did - and I was now stuck with 42kg of Chinese hardware. The Liang 845, was actually a disappointment, and did not deliver what I had hoped for. Again I approached Khun Kovit, with some idea's and he agreed to rebuild the amp for me. So when you now look at the pictures of my music room, then this is not a Liang any longer ( except for power supply and transformers - which are quite good). Kovit did a fine job, and except for a very slight hum, this amp delivers punch, speed and still quite a lot of the 300b magic. For more details about the rebuild, you may want to look at the enclosed file. Again - the internet is wondrous, and a Italian circuit published on the net, became an inspiration. Kovit in his final design did not follow this entirely. But let me say I am still very much pleased with the results.

By now I felt, that I wanted to try to build my own DIY amplifier. As I however have mentioned to you earlier, my knowledge and skill level is limited, and I am not trained to work with dangerous voltage. A Tube DIY kit was therefore not the right choice, as I had to learn a lot more before attempting such a project. I ended up building (assembling) a dual mono amp based on Hypex UcD 180HG modules (Class D) I found an old (and frankly speaking almost beyond repair) Hafler amp, in a second hand shop, which I acquired for a small sum, which in return became the perfect chassis for my project.
The Hypex is indeed a good amplifier, and together with my SacThailand TVC , my most " honest " equipment. The coloration and the addictive charm of the 300b and the 845 is absent, but the sound for my ears is neutral, true and good.

What I have learned in my room and from my setup over the past 2 years, is a lot about compromise, and quite a bit about speaker placement, room acoustics and finding the " right" combination of components.. I have also learned not to trust my ears every day and all the time. And I have learned that my Audio memory is limited, and not particularly reliable (especially true when entering "cable-land").

I did however find some tracks, and some setup procedures, which for my particular room work well, and which give me some pointers, what to look for. For a minute kindly assume that my system's resolution, indeed is quite adequate, and that the system is reasonable quiet. The rear wall has been dampened by heavy curtains and Thai pillows. Diffusers are installed on the ceiling, and sidewalls have enough open shelf space to do what they do in terms of reflection and keep the room alive.

I will now use one track from a Chesky test CD, where Chesky is asking whether microphones can record height. He moves a single shaker form the bottom, to the middle and then 3 feet above the microphone. It is with this track that I am able to position my speakers relative to walls and seating position, to obtain absolute pin point spatial accuracy. (There is a bit more to it - but let us leave it at that).
This procedure also works very well for the DTQWT's, and I am able to obtain very fine 3 dimensional imaging. And yes - the DTQWT is indeed engaging. I had a friend from Germany over last weekend, who also loves music and who also has a 300B - and of course he was amazed. I thank you very much for explaining the differences (Horn loaded speakers). This has set things in perspective for me.

Regards, HUH/Thailand

PS: I have been able to locate some small shops, which are doing speaker repairs. The first shop I tried managed to improve the damaged Pioneer driver to some degree, but the final result, after reinstallation was still not satisfactory. One of my colleagues recommended another shop, and they managed to realign the coil properly, so that it now can move freely. The downside was that the surround as well as the dustcap was replaced, with what was locally available, and the cone movement is now more stiff than for the original drivers - so some efficiency (maybe) was the price to pay. Anyhow, the driver is now installed, there are no more directly audible distortions, and after a good break in period, this will have to suffice for now.


March 2015:
Dear Troels

Maybe you remember me ... I build the  DTQWT speakers a couple of years ago and we had some correspondence
at that time., The speakers are still very much and happily alive and in daily use.
I cam across Diode Dick's webpage, and then later I saw what you had done based on the Little Caesar Circuit.
Both amplifiers have been an inspiration to me, and enclosed I send you a couple of pictures with my own take on the original design,
where I very much follow your 6SL7 solution, albeit with a tube HT power supply, and  all DC heaters
I finished this project about a week ago.... and so far so good, very quite, detailed, great bass and an incredible sound-stage.
All the iron ware was recycled from an earlier 300B amplifier, and the side panels and top alu sheet are from Ikea Bangkok's kitchen section,
whilst the front panel was a leftover claim from a China eBay purchase. Bits and pieces arrived at their own time and pace, and the final overall design
was determined by what  seemed to be right, and what I  had learned from the Morgan Jones books and what I could manufacture with
a corkscrew and a hacksaw.  One of my friends named it a " Storm P. " amplifier...... and since it's not a Caesar or a Gravesen.. I will gladly settle for that :-)
Thank you again for generously making your designs available..
This has brought me great joy, and sense of accomplishment.
Kind regards