25 June, 2024

Douk U4 PJ Miaolai A4 5670 Kinnie Antenna

Click pics to enlarge. Above is a Screenshot from Douk's old Ebay Page (now revised). Erroneously listing 2 chips, coexistence of both TDA1543 and PCM2704. But this historical page was likely passed down through the years, by ALL parties. In Japan (and elsewhere), this page is still used by vendors. BUT the photo is useful. You can clearly see the TDA1543 chip in this "Mk I" version. If you look at the pics of my unit, or those of the Jeff Day's clan, all are different
and the TDA1543 chip is not there ("MK II"). See text.

Right shows my unit used as Preamp

Review: Douk U4 (aka PJ Miaolai A4), Part I

Well, it's about time we tackle this little thing. There are several layers to it, all of which perhaps may surprise you.

How I learned about the Douk U4 This is an old and forgotten product which is apparently making a small resurgence, thanks to the influence of Jeff Day. Unless I'm in Research Mode, I don't usually read much internet HiFi, and Jeff Day not at all so it was because of a reader's comment that we got alerted of this thing. It's rare that I cite Jeff Day, but here are his posts on this thing (within them are links to older posts - make sure you read them too to get the piecemeal things). At the bottom of this article (a section in italics) are my general reactions to PF, Jeff Day etc. If you a PF or Jeff Day admirer you may not exactly like what you read but you can always skip the section.

Left pic is the Internals of My Unit. Top center black box is the Earphone receptacle. The chip to its left is the Opamp for the Earphone See more pics below for comparison. The 2 boxy "Wima" like caps are likely coupling caps and can be easily changed out.
Douk U4 Not unusual for Jeff Day's Blog, some of the details are not clear, quite lacking in fact. Compounding the problem is sometimes one is not sure whether it's Jeff Day or Yazaki san speaking. 

Let's start with what it is. This is an old model and Douk's boss was really surprised that I asked for it. Re-Branded As you know and as I have mentioned before, (competing) Chinese manufacturers sometimes re-brand each others' products (a curious practice indeed), and this is the case here. Although it bears the Douk Logo on the front plate it's actually an old PJ Miaolai A4 (which is also the name of the Bluetooth connection, and it comes in a PJ Miaolai box). For the sake of continuity (from Jeff Day's posts) so as not to confuse readers, throughout this post I shall mainly refer to it as Douk U4, but they are the same thing. Where to Buy The "Douk" U4 is sold mainly through Ebay Douk/Nobsound Official Store (shipped from China), not through TB, but it's interesting to note that: 1) there are other resellers. Japanese sellers ask for more, so this thing may be cult in Japan; 2) Can't buy the Douk from Chinese TB etc, attesting to this item's quiescent state outside of Japan and Jeff Day's reach). 但是香港及其它亚洲华人读者请留意文章尾的中文通告 "Mk I" vs "Mk II" These are names I give for the different versions. "Mk I", pictured at the top, apparently used the venerable 16-bit TDA 1543 chip, but " as implied" by the one liner at the end of the official description, after those old chips ran out it was changed to the delta-sigma PCM2704 chip (a long-running and time-honored cheap chip found in a staggering number of cheap USB DAC boards and finished products). ALL of the U4's you may have gotten in the last years, including the Japanese ones and Jeff Day's unit, and mine, are PCM2704 (see notations to pic above too). Yes, I asked Douk if they could find the "Mk I" in their warehouse but, alas, it was not to be! For myself I'd love to get a "Mk I" as I'm a fan of TDA1543! Perhaps one can get a second-hand unit on Ebay (one must check the innard's pic; see above)! Oversampling? As the old TDA1543 (used in "Mk I") is a popular Non-Oversampling (NOS) chip, I asked specifically whether the "Mk II" PCM 2704 is NOS, and I was told there is so. But I have my doubt, as the PCM2704 chip has built-in OS (I'm not even sure if it can be defeated). If you know more, let me know! Here, I must say I'm very disappointed, judging from what I read, that the Japanese clan, who have obviously taken this thing apart and even partially traced the tube output circuitry, did not include a word on the Digital Architecture. I wish they would!

Ergonomics Crazy Compact. A deck of cards with a tube sticking out. Well finished on the outside. But all the weight of connections in the back will tip up the front. OK for me, as seen in pic above I place it on a rubber shock absorber. Built It should be noted that in general PJ Miaolai is not the best-built, as evidenced by their preamp - and Douk boss' response. In my experience Douk's own designs are better built. But that perhaps hardly matters in a minimalist DAC of little circuitry. The daughter board housing the tube is affixed sloppily to the mother board underneath by pins which seem to be impossible to pull out even after removing the plastic screws (I tried) and therefore likely hard-soldered, preventing me from taking a look underneath. See pics above. Bluetooth It's the Lowest Common Denominator 5.0, SBC, but I don't mind that, as I'm not necessarily a fan of Apt X (more below), and I usually use USB. CAVEATS! The Bluetooth works mostly well enough for me (my devices are all long in the tooth) but connection difficulties do happen once in while USB Input Works well with my HP Laptop (no need for driver). I stream mostly directly from the laptop via a Unitek USB A to B (or whatever) cable. Headphone Output/Line Out The 3.5 jack is in front, as seen in top pic. This can be a very good Preamp Out too (see below). BTW, the Volume knob only works with this output. Using USB or BT it has no effect. Power DC12V. I power the unit not with the stock wall wart but with my Wanptek SMPS; it draws a little less than 0.3A.

Round 1 Shenzhen For Preliminary Testing I used the stock Russian 6N3, the RCA outputs via Belden 8428 to Reisong 1:1, which then outputs via Sommer SC Club Mk II (previously Belden 8451) to my 6J4/6P6P Preamp (now sporting old-stock US 6V6G), then through Belden 8451 to my BRZ FU50 amp and I was very pleased by the sound. Not as smooth as my 1-bit TDA 1305 but rhythmically even more alert and very good. I then tested the Bluetooth, which sounded good too, though to me it was some distance behind the USB. Good start!

The Douk U4 between the two parts of the Kinnie Bluetooth Player. As you can see, the very thin Antenna Wire (said to be culled from WE equipment) is connected to the U4. Bluetooth used with RCA Out. Also see one of the pics below for the mysterious Terminal Box of the Kinnie Antenna SMA connector.
Round 2 HK (above pic) After Round 1, I took it to HK at first opportunity. This actually took place in a visit I had chronicled (but didn't mention the Douk U4), Here it was pitched against the Kinnie Bluetooth Player. Suffice to say, on the Bluetooth while the Douk U4 did not have the fulsome flavor of the Kinnie it distinguished itself by its exceptional rhythmic clarity, and I was very pleased. BUT, there's more. The Kinnie set comprise the electronic unit and the BT antenna. We then transposed the antenna to the U4 and, HOLY COW, the U4 seemed to be on steroids! Sound fleshed out incredibly. I kid you not, this was one of my hifi moments of all time! What a difference an antenna makes! I'm even willing to wager a bet - that the Kinnie Antenna makes more of a difference than the cumbersome and expensive electronic mods proposed by the Japanese clan. I should make it known that I have never been a fan of battery power for audio (from small devices to mammoth ASR Emitter).

Round 3 Shenzhen Satisfied by the HK experience I proceeded to do more extensive testing when I got back to SZ. Using the same setup I tested:
  • Headphone Out I briefly tested it with my easy to drive Grado SR80E and it sounded very good! As Preamp Out (as in top pic) For this, I used my trusty el-cheapo DIY Canare 2B2AT 3.5mm to RCA cable. This is actually a significantly different configuration: 1) the signal passes out of the U4's own Opamp-based headphone output (the Volume Knob kicks into action); 2) I did use my Reisong 1:1, but its position is very different, now between Pre and Power Amp, whereas previously it was between Digital Source and Preamp. Sound? Surprisingly excellent! When I get the time, I'll pitch it against my real (all tube) Preamps and I bet it will do pretty well, despite being hybrid!
  • Tube Rolling JAN GE 5670 As I already have these (latter day tubes) I rolled them in. Sure, it made the sound more "mature", steady and textured. This is a very controlled sounding tube in general. For me, it's an improvement over the supplied Russian 6N3, but those who like things more incisive may think otherwise. For the TB price I think it's a good buy. Those savvy with Ebay can purchase used but good old-stock tubes or, if they are adventurous, splurge for the venerated WE396A/2C51. Amperex Holland 6DJ8 This has always been a personal fav, for its balanced flavor (as opposed to Mullard, Siemens etc). For this I had to order some adaptors from TB (https://m.tb.cn/h.gVjrcSxmwJVUJ4o). This is a very refined tube and what I use mainly. Again, some may still prefer the Russian 6N3 or 5670, and I think that it just bogs down to personal taste (we all  have different systems and play very different music) but good tubes are worthwhile to have. These tubes are worth to have. I have many other 6DJ8's including the UK ones, but I feel no urgency to roll tubes further (even the humble JAN GE 5670 works well enough for me).
  • Antenna After the seismic shock of Kinnie's remarkable antenna (Round 2), I was thoroughly convinced that, if you go BT, a better antenna is mandatory. Being in SZ I of course searched TB for all sorts of WiFi and Bluetooth antennae. There are many varieties. I randomly bought one but am not going to post any link as I don't really know what's better and cannot advice you. What I know is: 1) they are very crudely made; 2) yes, a better (at least bigger than the stock generic) antenna improves the results of BT audibly. In my setup even a cheap TB antenna made my BT closer to my USB in quality and the flow different! Those who have experience with FM certainly would know how much difference an antenna makes, and BT is close to radio frequency; 3) BUT, and this is telling, as good as the result was, it didn't seem quite as transformative as the Kinnie antenna, certainly not quite as big sounding. All that R&D had paid dividend! If you want the ultimate, I'm pretty certain Kinnie's antenna is a good investment, even a bargain.
Yes, it's a good unit and my experience (I'm happy to say, for once) is in accordance with those previously published by Jeff Day's clan. It makes me very curious about PJ Miaolai's D3, which is similar but differs in: 1) Despite the identical look, D3 uses a completely different chipset, including a receiver chip (again, here I wonder whether the A4/U4 is NOS); 2) D3 trades A4's USB In for Coaxial and Optical In, which may be better ergonomics for some. Another closely related unit is the (TDA1543) A7 amp (report to come soon).

  • Part II (coming soon) shall detail the experience of ELO and Shawn P. We each use it somewhat differently, so it should be a very good sequel. Just to say, sonically, their experiences are positive.
  • CAVEAT!  This is a BIG one. Its Bluetooth connectivity is finnicky, to say the least. And it has been experienced by all 3 of us. Funny there's no mention of this at all by Jeff Day and his friends. ELO experienced debilitating latency on some of his devices (and he tested his wifi and found it to be of good speed). Shawn could not pair some of his devices either. Read more in coming Part II. Reminder Even if the USB/BT switch is on USB, the BT is fully ON and discoverable, even possibly mating. When you have difficulty connecting, make sure you switch off all nearby devices, especially those that have been paired before. Try turning off device BT and on again. Think about starting with a clean slate.
  • Sound While we all feel its BT instability, we all love its sound. Rhythm King! The USB is excellent (all agree) and of course unlike BT is stable. Highly recommended despite its ergonomic shortcoming. Therefore, caveats aside, highly recommended (remember, it can also be used via earphone out as a good preamp)
  • Mods First, I already use it with my bigger adjustable SMPS unit, which has so far improves everything it's connected to - no exception. U can certainly use an LPS but I've always found a good SMPS of today (not wall wart) to be sprightlier. Battery? As I've mentioned, not to my taste usually. I shall certainly mod the 2 coupling caps and it will improve things. To go the Jeff Day Clan's way? I have serious reservations, given their previous track record (see italic section below). This thing's beauty is its rhythmic savvy; you don't want to turn it into the sonic equivalent of Belden 8402.
通告: 香港及其它亚洲华人读者请留意 暂时 Douk U4 没有在淘宝卖,但是一模一样的 (妙籁) PJ Miaolai A4 有, 618 有惊喜。上去淘宝找找!!!

Positive Feedback, Jeff Day and the Japanese Connection First and foremost, this is not a personal attack (though it may well be viewed as such by some). BUT, as I've voiced before, I almost completely disagree with Jeff Day's opinions on many things.

Let's talk about Positive Feedback first - many years ago, it was pretty good. Not now! I don't read it, just as I don't read 6moons, ad-laden and pandering to manufacturers. Sometimes, it's impossible to avoid but take it with a grain of salt.

As for Jeff Day, I believe he's an enthusiast, good at heart and certainly quite an influencer but I'm damn certain we don't voice our systems or listen the same way at all and so I don't usually read him

In passing, I should mention that as I returned to his blog I did read his latest article. For me, his praise of ANUK's Tomei is completely disagreeable - it shows no sense of the difference between EL84 (which although good sounding is not even a Triode, not to mention Direct-Heated), 300B and 211. Mind you, as owner of many 300B amps and the real Kondo Ongaku (211), I know what I'm talking about. Mind you too, my friend WSS still has the 211 ANUK Jinro, which had never sounded good. I can understand a reviewer sometimes needs find a certain way of writing an article but it's really unfortunate that Jeff Day chose to write it with ANUK's grading as fulcrum. He emphasizes the differences between Tiers, as ANUK would probably like him to (for my own view on this, see here). And, he doesn't even remark on how the difference in power output can affect the sound. IMHO, he's increasingly a careless reviewer. Too many toys, too little time. Too many "friends" who influence him too much, like modifying everything.

For irreconcilable differences I'll name 3 examples of discord. Belden 8402 As a signature post, I totally disagree with Jeff Day AND his Japanese clan's high opinion of Belden 8402 (and I'm usually a Belden fan!). Tannoy As a long time user of Tannoy Canterbury, I have influenced at least 4 acquaintances into buying it, and I have written a lot on it. Basically, I completely disagree with Jeff Day's Canterbury writings (lots of suspect tweaking) on this marvelous loudspeaker. Noting now that he uses the Westminster, I sigh. I have heard many Westminster's in Hong Kong but have never heard a satisfactory pair (icefox agrees with me and he's heard even more). For my reasoning and opinion of Canterbury vs Westminster, see this article (if you read carefully you shall notice that my approach to Tannoy is totally unlike Jeff Day's). As for Duelund? I think most are bad. Many are slow and lifeless with poor bass tactility, just like Belden 8402. I have yet to hear a Duelund that I like. Modern WE it is not. My NYC friend Andy says he doesn't hear any of the attributed strengths of this brand, quite blah...That's exactly what I think.

What about the Japanese? Ever since Jean Hiraga, many Western people have put the Japanese on a pedestal, but as HK audiophiles well versed in Japanese products know, many Japanese preferences are not necessarily close to ours. The large companies prize audio measurements and "cleanliness" more than most of us, and many of their products can be pretty much colorless. But the (mostly tubed) boutique companies are more interesting. There are many brands that I like (Old Sony CDPs, Yamamoto, Sun Audio, ICL/Softone, Wavac, earlier Kondo, early Elekit, Shindo preamps [not amps], 47 Lab, Sparkler, even Flying Mole, etc) and equally many that I dislike (TAOC, Esoteric, modern Accuphase, Furutech, ADL, Oyaide, etc). So it all depends. As detailed above, I completely disagree with the preference for Belden 8402 and so I'm sometimes wary of gurus in general. One has to take it case by case. In the case of U4, it did spark my curiosity (especially since it has a 6N3 tube) and so this outing, and I'm glad it has worked out.

Unit of Jeff Day Clan (like mine), definitely different from Top pic.
The Terminal Box of Kinnie's Antenna. I'd LOVE to have a look inside!


  1. I think I fully agree is the potential of this U4 is yet to be fully discovered! Wait until I plug in the DIY LPS

  2. Amazing sound coming out with a LPS replacing wall wart PS. Using iFi Power X on U4. Overall sound is really musical!