Douk U4 PJ Miaolai A4 Part III (Latest update on tube rolling 20th April updated in RED, Updated on 19th (Blue), 21st March (Green), 2025)

Letter from Hong Kong (25-1): ELO on  Douk U4/PJ Miaolai A4, again

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

Douk U4 Part I  from Doctorjohn has all the basic info.

Part II comprises experiences from ELO and Shawn P, chronicled in detail. It's actually fascinating, as always, to read about people struggling to make their gear work for them. It also shows how fastidious we are here in leaving no stone unturned for items we deem worthwhile (even if flawed). Compare that with reviews on the net (not to mention youtubers).

U4/A4 Again?? Not tired of promoting it?? Time for my WEA to step down?

Douk U4/ PJ Miaolai A4

It's hard to conceive that I was a skeptical  bystander about  Douk U4! Now, I have introduced this to many friends and they are all seasoned audiophiles with many years of experience and all were happy with the U4! But why should I keep promoting this unit, I dunno, I am not getting paid nor related to Douk and in fact I have never contacted them once! Ultimately, I just want to prove some principles in HiFi wrong and make HiFi lovers focus on music rather than gear. Many audiophiles use music to serve their uber expensive and flashy systems while music lover simply uses stereo to play music!

I keep hearing improvement over the U4 at difference places and I am expecting it will keep on improving at my place. Will the previously unshakable status of my trustworthy Wattson Emerson Analog WEA be shaken? We will talk about it more below.

This little Douk U4/ PJ Miolai A4 is like David in a HiFi World of Goliath's, where most buy stuff based on eye candy factor, size (over matter) and price tag (high enough to stroke one's ego) more than sound and Douk U4 is always fighting fearlessly in front of these Big Bosses ! 

Andy A newly met (online) friend Andy, who is also a long time NYC friend of Doctorjohn, has an illuminating comment on his experience on U4: he said despite many gear that can better the U4 in certain music genre, none can give him the "Thereness" experience of U4, the realness , the feeling of presence and "as if you are there " feeling, and that is what he treasures most from U4. He reckons tubes from WE sounds most real, perhaps I may look for one. (P.S., Tung Sol 5670, said to be OEM for WE , is on ordered for testing!)

Dr. Lo I brought the U4 to his place and at first his eyes betray his belittlement of this cheap unit, which is normal. But in the end he was surprised by the sound coming out from it! I played Tidal and Youtube through it using my Huawei P30 Pro phone (which I think sounds best compared to my tablet and laptop and other cellphones) as well as playing some tracks from Audio Technica's Sound Burger. Time from Pink Floyd left him in awe of the sound coming out from the formidable U4/SB combo! I left the unit with him to play around for a few days. In the interim, he was using the iFi Zen Blue Bluetooth and briefly thought it was better or comparable to my U4; this drew my doubts as I had previously sold my brand new iFi Zen Blue in less than a week. So I went to his place again to listen to both. Ended up we both agreed that the U4 was more engaging and musical; in comparison the iFi sounded a bit bland, nonchalant and uninvolving. The result further reinforced my belief~ Power Supply With a Ray modified PS that I had bought before the sound has beefed up with more flesh and blood and texture. Before I left, he told me another friend will come over to listen to the setup and I asked him to blind test U4 with his friend. Needless to say, his friend was pleasantly surprised by the sound coming out from this little unit! He said with a better Space and Time cable, the performance elevated to another level but I am confident my Sommer/Studer cable will not be inferior to it. I then asked if blind tested, will this unit beats or compare favorably with a $20k+ CDP, he paused for a minute and think deeply then nodded slowly and agreed.

Kwong Same happened to my long time HiFi buddy. I had asked him to try the U4 for months and to implement into his new home in China. He ended up buying a Pioneer Streamer and a Chinese DAC, which cost him over $10K HKD. He was happy with it until I almost put a knife on his neck to buy the U4 LOL. He then bought it and once plugged it in, he was very surprised by the SQ of U4, which was neck to neck with his current combo. One day, I gave him the Jan GE 5670 tube to replace the stock and as soon as he plugged it in, he never looked back and told me he immediately sold his Pioneer/DAC combo and used only the U4 as the sound sourfce and the SQ has surpassed his streamer/DAC combo by a significant  margin!

(Updated 20th April) Kwong bought a second unit for his main setup in HK and immediately , with GE tube, it surpasses the performance of his Lumin U1/Holo Spring 1 L3!! And now he is selling his Lumin !!! Also, the preamp fro  Fosi ZD3 also amazes him with the sound quality aand price

JC Needless to say, veteran JC, with the museum like collection of gear that he possesses~, along with his friends are all using U4 as their main source already and he is having tremendous fun on tube rolling and replacing LPS, cables (including USB) etc. 

Ah 7 Another friend Seven had bought it based on my enthusiastic recommendation but was too busy to listen to it since he had been on graveyard shift lately, poor him... Finally he texted me that he was so excited by the sound quality of U4. Exactly like me, he put it aside when he first received it, and was skeptical of this little unit..... then eventually the GE JAN tube arrived and he started to plug it in and listen seriously and what a transformation, the sound absolutely surpassed his Eversolo A6 (replaced LPS) and Holo Spring 2  DAC! He is putting them up on sale immediately, which shows how good this little U4 is! He then decided to up his system and today he changed all his cables to Sommer/Studer/Neutrik and needless to say, the whole performance has elevated to another level!  

Extract of his comment:

依家越聽越好聽

部數播同泉都可以收工了

部eversxlx真廢，重要換埋火牛

都輸比藍芽U4

幾舊水對琳左幾千銀部機，過唔到自己心理

我仲未煲好，冇聽夠時數

但已經要打算賣機

(Updated on 21st March)

Ah BUT, I went to my primary schoolmate's place  for a wonderful music gathering focusing on songs rather than hifi. Four of us take turn choosing a song to play of each's own favorite choice. A lot of oldies and some jazz songs were played and we had a great time. I then introduced U4 to them, ah BUT ordered one immediately and was so shocked that the sound quality matches his streamer/DAC combo! He reckons his combo still has an edge on classical playback, but U4 is as good in jazz and vocals! I gave him the Tung Sol tube which sounds warmer and more musical!  He has then ordered the PS from Ray as well too!  BTW, his combo is Grimm's MU1 and Playback CDP's DAC that costs close to $200K HKD or $25K USD vs U4 which costs $200 HKD which is almost 100 times cheaper!! Well done U4 in performing another David and Goliath act! 

Me From the beginning till now, U4 has served as a reliable source at my home for watching TV and Youtube videos and playing records from Sound Burger. But initially I thought WEA clearly had the upper hand when streaming Tidal and I deemed the gap to be significant. Power Supply But how would the U4 sound with the New PS from Ray and with Sommer/Studer cable, will it dethrone my WEA?? 

More Comparison I was ready for the face off of U4 vs WEA. I used the newly bought Luxman AS-4III line selector ($700HKD) from Yodobashi in Osaka to resolve the issue of only one input of E6.

Setup A - Tidal using WEA, iFi Power Plus PS. All resting on graphite plucks and with body connected to ground box. All cables Sommer/Studer (with Neutrik connectors that brought significant improvement over stock KLE ones); Setup B - Tidal using Huawei P30 Pro phone to Douk U4 powered by Ray's PS ( All Sommer/Studer).

And that's not the only thing. Icefox, DJ and Andy (DJ's long time friend) all told me to also try the headphone jack as output. I first heard it that way at Mila's shop - not much impression as I was not familiar with his setup and his audio preference seems slightly differs from mine - so I could not make a judgement. I went home and tried it myself and here's my finding: sound seems to be smoother with improved body , more musical too when I connected to the headphone jack; however, that is with a cost -  a loss of certain degree of clarity and shrinking of soundstage as well as less quiet background. Fish and Bear Paw, I chose the latter, i.e. RCA out at the back.

As mentioned, I had finally taken the plunge and replaced the KLE connectors of my last two set of Sommer/Studer interconnects to Neutrik . The effect on U4 playing Tidal music from my laptop is really promising; the sound from RCA output has further improved with added nuance , musicality and silkiness. 

Tidal Tracks I played to compare: 1) Paris, Istanbul, Shanghai by Joel Glare; 2) Bach III Gavotte and Rondeau by Nathan Milstein; 3) Love letter by Jacky Chan; plus many others. 

Initially, switching A/B, sound was neck to neck, which really surprised me, as this was the first time that my WEA was seriously challenged , which is indeed a shock for me since before there was a big gap between WEA and U4 !

In terms of sheer musicality , details, smoothness, balanced sound through high, mid and low spectrum, the U4 was neck to neck with WEA! At one point I could not decide which setup is better!!! That was the FIRST time in my memory. 

So I did one thing, I unplugged the WEA and decided to spend days to listen to just the U4, streaming Tidal, Youtube through TV. Needless to say, I was very happy with U4 and for once I had forgotten the WEA completely since it was so convenient to use!

Until...a few days ago, I thought it was time to shift back to my WEA. I think that would be a fair comparison since I had become so used to U4's sound by now!

And the verdict is...WEA still has the upper hand! That said, U4 did most of the things right or even superbly. The WEA only beats it in the additional clarity and the emotional connection in strings (Erhu with WEA is definitely more engaging and can trigger my inner emotion far more than U4 or any other setup I have heard). That said, for most other types of songs, U4 is very comparable to WEA.

Violin from WEA is among the best that I have heard; it can grab my heart and soul ! I'm afraid U4 , while very very good, cannot match the final touch of WEA but is damn close (Before I use WE396A on U4). But consider U4 is selling at a fraction of price, there's no shame at all, it's just that WEA is such  a wonderful little machine from the Swiss that in itself is a certain David in front of bigger Goliath's!!!

Updated 20th April: TUBE ROLLING

Who would have thought I'm into this! My first time but man that's addictive! I have now 5 different tubes and they are (though I have yet to try 6NS7 like my friend)

Stock : A decent tube given the price

GE5670 : Improves overall sound by 20% from stock and is a cheap upgrade

Tung Sol 5670 : Very euphonic  and tends to gives a sweeter sound which is welcoming to a lot of harsh recordings but at the expense of shrunk soundstage and clarity. But I can live with the loss easily

Electro Harmonix Gold 6922 : Bought a tube adaptor to try this on. Immediately, the soundstage has widened and things get more transparent and a bit more dynamic, less euphonic though comapre to Tung Sol

WE396A: I finally received a replacement tube since the first one delivered was defective. This tube is so neutral but in a sense is pure, without adding or taking away things, Good spatial interpretation, smooth but not lush, and is pure and musical in a natural form.  Achieve a lot by not interfering with the recording! I like it a lot especially when playing LPs from my Sound Burger, the soundstage is huge, dynamics is superb, violin is lean yet clear as spring water with accurate timbre, probably the best format at my current setup! Add in the Uptone Ultracap LPS1.2 further improves the macro dynamics and dynamic shadings of the music. Music seems to calm down in a good sense! This is the best tube so far! For $3xxHKD bought from PTT, it's a steal!

Conclusion (updated 19th March and further update on 20th April) 

I will NOT put a conclusion since both U4 and WEA are such wonderful bargains in today's mad mad Hifi world, where a power cable can sell for 700K to 800K HKD!! I leave it up to you to make a conclusion for yourself and examine your motive towards "playing HiFi" (Chinese term in listening to HiFi). (Updated 20th April): In addition, Sound Burger through U$/WE396A and Uptone produces the best sound ever at my place and I am truly amazed!

Music First, with sufficient Hifi attributes - that's always the only way!!! Until then Adios Sis and Bros.

I surfed through "Leisure Fish", Carousell equivalent of HK and while looking for WE396 tube to replace my GE5670, I came across these old stock Tung Sol 5670, said to be OEM for WE at such cheap price $110 each, bought 5 of them to share among friends. Tonight , I plugged it in and replaced my GE 5670 on U4. Immediately, there was a significant different that can be detected ! The sound has become more coherent, more organic and I hate to use the generic term "musical" but seems appropriate here. Music from singer and instruments played with more  oneness ,sense and pace. Violin has more of wooden box resonance and body, notes between notes are more connected to become more fluid. However, in terms of HiFi terms, there is a sacrifice of ultimate clarity , space and width of soundstage but if I did not hear the GE , I would not have spotted that!  As of now, U4 has this added weapon and can now stand side by side with my Wattson!!! Bravo!

P.S. My WEA suddenly doesn't work for me all of sudden after a rock solid , no-glitch operation 24/7  and man , do I feel so grateful that I still got my U4/Tung-sol tube with me while debugging my WEA!!

WEA suddenly works perfectly with no reasons but is more than welcoming. 

Thanks to Deep Seek's recommendation of Shungite crystal! I just bought some and placed it on top my WEA and mixed some with tourmaline in one of my gorund boxes, all to good effect.

I had replaced the original box with a beautiful inlaid wooden box~

LCY Supertweeter , Room Imbalance Acoustics, Home Visits

Letter from Hong Kong (24-19): ELO Home Visits and LCY Supertweeter

Editor: As mentioned in my last communication, starting with this article my editing of others' articles shall be minimal. Regular readers shall notice the difference.

As a HiFi lone ranger I would call myself, I mostly work on my system alone but of course Kwong is my long term trusted HiFi companion sharing same belief. Dr John is another one whom we get acquainted when I start reading and commented on his posts, eventually writing here occasionally. Icefox is the walking Baidu/Google search of HiFi (the word encyclopedia seems obsolete in today's world hence not use here LOL and Dr Lo , a high school classmate and also is a seasoned audiophile with his own unique hifi path~

I do participate in a few small private hifi chat groups talk about mostly music and some HiFi stuff but home visit is very limited either to my place or visiting others setup.

Recently , I have met some really nice hifi lovers who had selflessly given me some constructive advice which helps to improve my setup! 

Home visit to my place by a Hifi Lover

I met JC when I bought the LITE DAC a few years ago, which has a cult following and a dedicated discussion forum on modifying and opamp rolling! 

On and off, we have been exchanging txt messages and I showed him some photos of my rig from time to time. He has then shown some interest and wanting to hear it. Seldom invite new friends over to listen to my setup and is a great opportunity to let someone who is new to my setup to give some constructive advice. In the end, it went well, at least he did not complain, or perhaps refrain from it. Instead, he was surprised by the realness of playing Youtube music and analog setup using my new toy Sound Burger from Audio Technica both via Bluetooth from my Douk U4, which he had never given a serious look at  music from Bluetooth before .

JC was inspired by the sound playing Youtube music videos from my system that he pulled the trigger and bought one along with the TB retro looking antennae. His downstairs neighbor who is a researcher on BT and satellite transmission, said his BT controlled model plane can fly from Kwun Tong to TKO under control thru BT signal which is a full 4 to 5km distance apart!! Perhaps I should ask him to design a BT antennae for me~ 

Later, he connected the PJ Miaolai A4/Antennae (PJM A4 is equivalent to Douk U4) to his system where he found the sound to be very analog and musical ! Stock antennae tends to be more hifi but thinner and with more digital harshness in my opinion. Ultimately he thinks the stock cheap one has better high extension and openness. My comparison of the stock one and the retro sci-fi looking antennae and my findings is that the retro looking one is far more musical in my setup that I am willing to sacrifice the high frequency extension.  Everyone will have their own setup, taste and preference !

He then invited me to his studio which is at a stone throw distance to my office, his place is like a museum with a lot of collectable gears inside, yet the sound does not sound a bit dated at all! Learnt a lot from him and he spent a lot of them explaining and hinting  and finally got me hooked up to a super tweeter which is another story to tell which I eventually bought a pair of LCY 100Mk2 and is still experimenting with it and the journey has just begun...LOL

I think he is now a happy camper of A4 despite he much prefers the black colour to the uglier looking silver version LOL! I told him he can change the sound be replacing the capacitors of A4 but instead, he uses the best cables to test it which I think purely for fun. The lineup is VDH MC Silver Mk2 plus and Habst USB cable.....costing more than the costs of 100 units of  Douk A4 and he said the performance is many folds better! He also did some tube rolling of many tubes and found out WE is of best result while I'm enjoying the one from JAN 5670..

Room acoustics - Room imbalance and imaging

I have met another really nice gentleman on R33 and he generously share his own knowledge on speaker placement. His belief is once speaker is positioned properly, you don't need to buy uber expensive gears ! I haven't started to implement his guide but it did triggered me to solve the problem of my uneven spaced living room with one side sticking close to glass door to my balcony and one side is completely opened up! But luckily , I suddenly remembered that my Dynaudio Crafft has some gain switches and I immediately tried to reduce 3db on both highs and mids of my left speaker against the wall and the imbalance towards left side has switched back to middle! Originally I only tried it to adjust gains simultaneously on both speakers but not just one unit. Previously, I had tried toe in left speaker but effect is minimal, so the gain switch does help immediately and if not this nice gentlemen triggered my determination, I would have never fixed this chronic issue.. LOL

As a return favour, I introduce him a Hifi absorbing/refection board manufacturer in Taobao which he can customer made with dimensions, shapes , patterns and colours to fit your own need!! That was actually another discovery from Kwong, my long time Hifi buddy!

Revisit to Dr Lo's home

The only change but a most significant change is to install a dedicated German custom made speaker stands for his Harbeth P3SE Special Edition and it costs him over a whacking $10000HKD!  Well, it all worth it and the results is really great, now you find quality bass that is missing before and the analytical power has increased with tons of micro details being revealed!

Conclusion

It's always nice to meet new hifi lovers as it will always give you something new , inspire each other and can improve the performance of you setup with all the constructive ideas, of course there will be trial and error in this process which is inevitable! 

As usual here's some of my latest street works~~

PJ Miaolai A7

Review: PJ Miaolai A7

If you are a regular reader and just casually glimpse at the large pic above, you shall be excused for mistaking this article to be a continuation of our Douk U4/PJ Miaolai A4 reports, but blink and stare again at the speaker binding posts! Yes, in the same tiny chassis, this is a complete amp!!!!

Let's see some Official Spec's:

A7 Parameters:

Audio input terminal: 3.5AUX stereo input, Bluetooth input

Voltage input: 12V

Rated output power: 8Ω 2*30W; 4Ω 2*50W

Headphone Amp Parameters:

Rated power output: 150MW+150MW, impedance 16-300 ohms

Distortion: THD+N: 0.004% (RL>10 kΩ)

Distortion: THD+N: 0.020% (RL=32 Ω)

Signal to noise ratio: >99 dB

Dynamic range: >99 dB

TPA3116 is a class D power amplifier IC, which can reach a modulation frequency of up to 1.2MHz. It has the characteristics of low power consumption, high efficiency, low distortion, and strong reducibility.

-The Bluetooth 5.0 module uses the QCC3008 chip, supports APT-X, APTX-LL. The decoding line uses the classic 1543 chip, and the external high-gain detachable antenna makes the sound quality low-latency high-fidelity lossless transmission.

-The headphone amp part uses the classic MAX9722 audio decoder chip.

-Adopt 6N3 tube, Bluetooth QCC3008 chip + 1543 decoder chip.

The now-forgotten A7 is definitely a cousin of the same company's older version A4. In fact, the relationship probably stemmed from really early on, when the TDA1543 chip had not yet run out. As we have emphasized in the Douk U4/PJ Miaolai A4 (U4/A4) threads quoted above, their current products do not sport the classic chip. And so we came to why I bought this amp - in the hope that its obscurity (nothing on the internet, and deadwood) means that I can get a TDA1543 product. Result? Well, I'm not sure at all! Read on...

I bought it for a very tiny sum during TB 618 (less than a bowl of wonton noodles in HK). The first thing I did when I received it was of course to open it up (hence the pic above). It's construction is very much like the U4/A4, with a daughter board housing the tube. Unfortunately, it's also seems to be hard-soldered to the main board via many pins. Again, this precluded my taking a good look as to whether there is a TDA1543 chip around. It's also amazing that the very limited space there can house an amp. Kudos to digital amp!

Facilities are very limited for this tiny amp. You have BT and 3.5 Aux in, that's all.

Earphone I didn't test it out, but I expect it to be exactly the same as the U4/A4, which is very good.

Bluetooth It shows up as PJ Miaolai (no, not A7, nor A4 etc), and seems to be very similar to its sibling A4 (Douk U4). Connectivity seems the same, that is with hiccups sometimes (follow the previous threads) but I'm OK with my old Samsung cell. I wish Shawn P and his App are around to tell me what this BT is, SBC? I'm pretty sure it is. Apt X support? Doubtful. But then, how good is the BT sound? Supported by a TB BT antenna, sound is as good as U4/A4, perhaps even better. The A7 is now permanent in my setup with the Sansui. It's good enough to have shifted my playback habits to more reliance on BT. When the sonic qualities are not so far away, BT can be very attractive.

Aux 3.5 works perfectly well and sounds very good, of course. I could have tested this input more but I didn't.

Power With only a 12V supply, the claimed output is likely way too optimistic. BUT, matched with my efficient Sansui speakers, sound was beyond reproach! With such limited real estate and minimal components, I'd think twice about increasing the voltage of the PS. It survived my 24V (very brief) but I'd not vouch for it. This 12V (rated at 4A) seems to be fairly powerful. But then my loudspeakers are efficient. It also drives my Beydas well enough.

Sound This is the million dollar question! I'm glad to report that it is very very good, provided you make a few adjustments: 1) I did not even use the stock Russian 6N3 and went straight to the JAN GE 5670 (see our U4/A4 threads); 2) it needs a bit of run in to smooth out some roughness; 3) it needs forgiving loudspeaker cables, like that provided by my "Belden 1309A" 

So? How good is that? I'm not sure how to say it. It's good enough to be a Reference here. In fact the A7's arrival significantly changed my setup here in SZ. It is now a permanent fixture for my Sansui loudspeakers. It made me use BT. It does not have the tonal generosity of my all tubed amplification but it makes up for it in its crisp and incisive delivery. THAT is a good few watts!

I'd reckon I'm hearing some of the TDA1543 qualities (supreme rhythm, at the expense of a little grain overall) but, since I cannot get to the part of the main board under the daughter board, I cannot vouch for it. If you do, let me know.

What I do know is that, this is a great little achiever! If your loudspeakers are efficient and the very limited input suits, think of trying it out. I haven't compared directly, but I'm pretty sure I prefer it to the Aiyima T9.

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

Update 7/23/24: Part II published, featuring experiences of ELO and Shawn P, including latency and BT problems, etc.

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 that 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).

Thoughts

• 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!!!

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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.

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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!

Douk T8 Pro PJ Miaolai SA-1000

Click pics to enlarge. Douk T8 Pro. If this were a US or UK or EU Brand, even one manufactured in China, it'd cost at least multiple tens times the cost! Bottom, Knobs. Far right is the Balance (nice!), which can only be turned by a Philips screwdriver. Second from right is main Volume knob. To the left are 7 for Equalizers. Far left is on-off switch. Behind the Volume knobs and near the tube sockets are 3 JRC2068D Op Amps seated on sockets. The ones behind the Euqalizers are N5532. The Tube board is removable so one can modify the caps, but there are so many of them I have no idea what is what! Maybe time to find out. 

Letter from Shenzhen (24-2): 3 Preamps, 3 Amps and 2 Loudspeakers

Douk T8 Pro, Part I

Douk T8 Pro, Part II here; Part III (on XLR use) here.

Why should you be a long term reader of this blog? It's very simple. Aside from the fact that very very few trade or e-sites refuse monetization (think the garbage ads 6 Moons pile on you page after page, which is why I hardly read them and try never to cite them - I despise them, and shame on you if you read them regularly for free without thinking about your mental cost), very few audio sites re-visit audio equipment regularly (Stereophile commendably has some periodically and HiFi News has very good referencing to older versions too).  Very few sites even mention older equipment (Thumbs up for Stereophile to continue to upload their vintage contents, and HiFi News to have Tim Jarman's Column on vintage stuff). We do here, and we sometimes re-think our opinions. And you shall find some examples below if you read carefully. Grant you, we mostly "review" el-cheapo new stuff or re-visit older stuff, but we do it very seriously. We tell it like it is, over a long period. This article is both an update on some equipment previously covered, as well as the introduction of 2 new Preamps. Not earth shattering things, but interesting nonetheless. As for music, at least for classical aficionados, our coverage is concise but very good.

In fact, I think the best thing about our approach is to tell you how to go about it, or rather how we go about it, not what is better than what. One can learn from the most simple experiments. To achieve good sound, one must listen a lot and read less (apart from this site, since it won't empty your wallet, LOL). Especially, you should not read sites like Audioscience. The measurements are OK, but the opinions are trash. Subjective evaluation is kintergarten level. I have only contempt for them. But they sell. It's a pity Chinese manufacturers routinely send things to them, even high end stuff like Matrix.

First, some catching up, or what I'm doing.

2 Loudspeakers (Beydas/Stirling LS3/5a Redux)

I direct you to my article that describes when I just came back from the US a few months ago. My Beydas "LS3/5A" "11 ohm" (basic info in Chinese here) sounded deadly dull. And I spent a lot of time to get the "old sound" back. It came back eventually, but I never was sure of why. Such are the vagaries of HiFi sometimes (whole process described here).

BUT, I got a new angle maybe a month ago. I swapped in the "15 ohm" Beydas "LS3/5A" (basic info in Chinese here), and the initial sound was not good at all either. Yes, more open in the treble (it has always been the case) BUT seriously deficient in mid-bass and bass ("official spec" has it as 10 db less extension than the "11 ohm"). Now, this was a virtually new pair, because when I went back to NYC last time, I gave my run-in pair to Andy. As I ran them in over a month, the sound gradually became fuller and some useful bass emerged. Right now? It's marvelous! I just listened to Sibelius Symphony No. 4 (Gothenberg SO/Rouvali, Alpha). This is a heavily brooding piece. Although this version is distinctive and lighter than usual, the double bass must have impact and, when partnered right, it does. In absolute terms, with the 3/5 it's just a hint, but that is more important than anything else. A hint of deep bass is a tactile and suggestive bass, very worthy (even the real LS3/5A is like that too, just a hint). Wonderful!

Yes, right now, despite the lighter bass, the "15 ohm" sounds better than the "11 ohm" but it had on occasion been the opposite before. One thing I did think of: If you haven't used a loudspeaker for a while, it takes a while for it to re-capture its former prowess. YMMV. But, if you use flea powered amps like I do, it makes sense.

2 Amps (BRZ FU-50 and SE 6L6) and Another (APPL 300B) Redux

I had spilled much ink on these 2 BRZ amps, and they remain my daily staple. It's really astonishing how much improvement I got from "upgrading" the stock Rifa caps with USD 0.25 "Solen" (here). Both opened up considerably in soundstage as well as enhanced in tonal opulence! The FU-50 (basic info here) remains ahead in most respects (though the 6L6 [basic info here] is likely fuller in the bass). Both are just super bargains! Now that kits like Elekit (which I have long championed before but have reservations now) have gotten over-expensive (and unnecessarily big) I'd urge starters to consider these 2 very cheap amps (that come with useful tubes, not as extras). Mind you, like my favorite Sun Audio, these are simple, pure tube in the signal path (which I usually prefer, but not always), whereas Elekits now are very much solid-state-regulated in the control grids to achieve higher power and better dynamics. I actually have no qualms about things like solid-state use like constant current source (my ICL amps use that); it all depends on the resultant sound. I do think I can hear a trace of ss influence in the Elekit, but not in ICL. As for the cheap stuff here, as you can see from the links, aside from swapping in other tubes (still cheap), IF you can solder and change just a wire or two and swap a cheap cap in you can gain a lot!

Unlike Aiyima and Douk, with whom I have some kind of loose relationship (always declared) I have none with BRZ. In fact, I probably frown upon BRZ's voracious replicas of solid state FM Acoustics at super-bargain prices (though I'd not mind to hear one in my own setup if I get the chance). Price is their advantage, but I do believe they have a certain know-how: to make the best sound just above the technical safety red line (and that is why I'd NOT recommend you to plug in KT66 in the 6L6 amp; I have GEC KT66 but I'd not use it - also as US 6L6GC sounds just delightful in this amp!). Within limits, these amps run in my system hours a day for months without any problem. That's good! I've QC'ed it for you (and my samples are like yours, just randomly ordered from the net), provided you stick to rules.

But hierarchy remains. The Ultralinear 6L6 (or EL34) is still not as tactile as the FU50 run as Triode, and the FU50 still does not have the full sized presence of the APPL 300B amp (here, as yet still bone stock!). But switching between them is fun, and it reminds one that Ultralinear is not quite Triode, and running a Tetrode/Pentode as Triode is not the same thing as a Direct-Heated Triode. This has always been my long-term belief and this humble trio actually confirms it. There's no end to comparisons, and this blog compares more stuff than others. My point is you can learn a lot from even cheaper equipment (provided they are good). If you buy all 3 of these it's still way cheaper than a stock Elekit without tubes, but I wager you learn a lot more.

New Production Tubes

ALL these sellers out there say to you, this 300B is better than that one but few of them have really heard the old-stock WE300B's. I tell you ANY new one will not match up against old stock. I refer you to my recent article. That's not a sound you can get from buying an expensive replica tube today. So much nonsense out there it's really astonishing! IMHO, one should start with an honest and reasonable modern 300B tube, like the affordable Linlai that comes with my superb APPLause 300B amp, or a Russian basic tube. All so-called upgrades, like graphite or mesh plates, or gold pin this and that, sound different, but better? Not to me. YMMV. New "Western Electric"? Takatsuki? No thanks to all of them. In case you're interested, here's a 300B Shootout, from more than 20 years ago, LOL!

If someone has the dough, more power to him! Spend a lot on tubes is OK, but I'd buy only old-stock tubes (for 300B, WE before early 80's). Even if I have the dough, I'd NOT buy any of these boutique replica power tubes (be it 300B, 2A3 whatever). This is to emphasize that it's ridiculous for someone on a budget to spend more on tubes than the machine. Put the ridiculously priced current production "WE" 300B in an Angela amp and it's still an overpriced mediocrity. Better, put them in an Elekit, but it's still an Elekit. This is true for boutique components too, be it expensive caps or resistors or even transformer swaps. There is only so much improvement one can get from tweaking. Cheap mods are a lot of fun; expensive ones almost always end up in disappointment. No matter how you mod a Subaru it will not be a Ferrari; better enjoy the Subaru as it is!

Unlike most reviewers out there, I have been a tube addict for over 30 years, and I have a huge stash of very worthy old-stock tubes (and even more lesser ones, LOL!) In terms of tubes, I can max out the potential return in almost any amp. I can tell you what's a worthy upgrade and what is not. Driver tubes are worth experimenting with. As one goes down the line, the tubes become more useful. It's always good to have a few 12AX7 and 6SN7 around, for example, as they are used in so many amps.  I sympathize with beginners on a budget. They read everything on the net, and end up buying different Russian and Chinese tubes of little import, when they should take the bigger step and bid on some good used old-stock tubes on Ebay etc. Power tubes are more problematic but, as I say, I find modern boutique tubes underwhelming. As mentioned above, I'd not spend too much...Last, incidentally, personally I feel Russian and Chinese 300Bs are very good tubes because 1) they have been making these for decades; 2) perhaps Triode are easier to make than Tetrodes/Pentodes with their additional elements; 3) I bet you Chinese 300B parts are used in many other boutique 300Bs. There is a huge amount of undesirable trade secrets out there. As for other DHT like 2A3 and 45, modern ones are just basically tweaked out 300Bs.

That's a lot of digression. Now to the Main Course.

3 Preamps (Eastern Transmission Audio [ETA] 6N3, PJ Miaolai SA-1000, Douk T8 Pro)

This came by in an unusual way. As I tube rolled the BRZ A08 6L6/El34 Amp I employed some better sounding but lesser gain tubes, like the 6SN7/L7 (with adaptor). As detailed in the link above, I prefer the larger envelope tubes (as usual). Which means there's an opportunity to use higher gain tube preamps. As mentioned in the link also, I tried the ETA 6N3 Preamp, but its defective volume pot makes it impossible to get a proper volume.

So I dragged in another two candidates...both are hybrids, tube buffered IC Preamps. Both are debutants here.

https://m.tb.cn/h.5rIMhYx5izOLuU2

PJ Miaolai SA-1000

I actually still don't know why I bought this. During a previous 11.11 it was just so ridiculously cheap at barely over 200 RMB (around USD 30) that curiosity got the better of me. I actually got it before I got the ETA 6N3.SRPP Preamp. Reason? This came with a pair of Russian 6N3 so I later ordered the ETA without tubes at a savings of 50 RMB. Cheapskate, yes!

This is a Preamp, with 4 Inputs and 2 Outputs. It's based on the N5532 Opamp (not easily replaceable). It sports dual Tone Controls and Headphone Output. It runs on 12V DC (I used my own heftier SMPS PS). One Russian 6N3P in each channel serves as buffer (probably just paralleled, unlike the ETA's SRPP). More in pic at bottom. BTW, there is a new version with Bluetooth and remote control. Caveats The RCA sockets are of the most "basic" quality, which is true of many Chinese products at this price level. The outer casing of one got stripped as I pulled my MIT T3 interconnect out. Yes, this happened to my 6J4/6P6P preamp too. On both, 1 down, 3 to go. Make sure you don't use connectors that grip too tight.

When the PJM arrived, I fired it up and was assaulted by the crazy high gain and grainy sound and basically put it aside for a long long time. I never thought I'd write about it. I basically wrote it off!

Fast forward. I poached the stock Russian 6N3 for the ETA Preamp. At first, it was not so good, but after some mods and a hiatus, it was suddenly OK (chronicled here). And so I enjoyed the ETA for a while.

Fast forward to now. Since I could now use a higher gain preamp with the BRZ 6L6 Amp I decided to give this PJM Preamp a try. I put back in the 6N3 Russian tubes and was surprised. Perhaps due to the fact that I have run the tubes in thoroughly in the ETA, it had become much smoother. In fact, the run-in Russian 6N3 (and perhaps the run-in preamp) seems to be be fairly smooth. Too bad I don't have any WE396A/2C51 or even 5670 around (not even in HK).

vs ETA Comparison with the ETA (both using the same set of Russian 6N3) was fascinating. The all-tube circuit ETA (SRPP), which has had its caps and hook up cables modifed (link above), sounded not quite as fast as the also high-gain PJM. But the basic sonic signature is very similar, not surprisingly since they use the same tube. The midrange is virtually identical. The ETA has a little more top-end air and nuance, but turning up the Treble a little on the PJM brings the two closer again.

Headphone Output I tested it with my Grado SR-80E and it was decent enough!

https://m.tb.cn/h.5qKXYRImLH9oJ04

Douk T8 Pro (7-Band Equalizer Preamp)

This is a fascinating one. It stands out for having a 7-band Equalizer. Also, it has both Balanced (XLR) and RCA Inputs and Outputs (just one set each). My unit is on loan from Douk. Again, this is an Opamp based Preamp (JRC2068D and N5532; see top pic for more detail), with Russian 6N1P buffer. Runs on 12V DC. Price is around RMB 650 (USD <100)

I don't have any balanced stuff here in SZ to try it out, but keep in mind that it can serve as an XLR to RCA convertor and vice versa.

I ran it first with the stock Russian 6N1P. Sound was surprisingly decent. Even then, I noticed that the sound is faster in transient than either 6N3P Preamps above. As I use my own SMPS PS with digital display, I noticed instantly that this preamp draws a much higher current than the others. At turn on, it transiently hits even 1.5A, but very instantly normalizes to just under 1A. Not surprising, as there are a total of >10 Opamps in the signal path alone. This is double the current of the 2 preamps above. With all the Equalizers flat (12 O'clock) sound was a shade plain, perhaps even betraying its opamp origin, if just a shade. So I proceeded to:

Equalizing The Equalizers are centered at 50, 125, 315, 750, 2K 6K, 16K Hz. I'm not at all a student of equalizers, so I don't even profess any knowledge about whether these are effective points, well chosen or not. I also don't know the slopes nor the +/- db offered. Just like how I dial in subwoofers, I think these should be used judiciously and with great restraint. As my system is fairly balanced and neutral, I felt no need to equalize at either end. Instead, I almost on impulse, and randomly, bumped up the 750, 2K and 6K to around 2 O'Clock. The idea was to raise the (upper) midrange a little. Well! It worked better than I thought! First, the slight paleness filled out. Any negative effect of Opamps was diminished. These settings worked for me, but for your system it might be otherwise.

Tube Rolling Unlike 6N2, where you have to use an adaptors to roll tubes, and unlike 6N3, where there are few substitutes, 6N1 has pin compatible direct substitutes. You can directly plug in 6DJ8 (family) and 6CG7. These are tubes that many people who play with modern stuff like Schiit have in their arsenal. I just happened to have brought some of these over for my BRZ amp tube rolling using 6N2 adaptors. 6DJ8 The Amperex Holland brings about a much greater refinement than the stock Russian 6N1. 6CG7 But my heart belongs to these. The Matsushita were a shade dry, but the GE proved just about perfect. Moist, but dynamic and refined. Now, where are my RCA Clear tops? Tube rolling effect is greater than equalizing. Some people would say that, though pin-compatible, these are not exact equivalents. But, why worry? This is all about equalizing, right? After I rolled in the 6CG7 I felt absolutely no desire to roll others and proceeded to compare:

vs 6N3 Preamps The Douk sounded so right that I totally forgot it has Opamps in it (especially when equalized). The low strung PJM didn't really sound transistory but in comparison was less three-dimensional, and smeared in terms of imaging. Even the all-tube ETA fell behind. By a good margin, with the transient sharpness, airiness and good tonal control, the Douk simply sounds more present, and involving, and by a good margin.

vs Douk E6 This article took a long time to write. I compared the participants multiple times, both with Russian tubes and with tube rolling. Now, with everything going on, I haven't fired up my Douk E6 in ages. Despite its quirkiness regular readers know how much I respect this little gem. Suffice to say, equipped with the GE 6CG7 the Douk T8 Pro did not loose too much ground. Best, it conveys the drama and narrative in the music as well. The E6 is for sure a little airier and luxuriating in the treble but not by as much as you think. That translates to great praise for the T8 Pro.

Suffice to say, lately I have been largely using the T8 Pro. I periodically rolled in the ETA and the PJM but I always revert back to the T8 Pro. That says a lot. I think I'd purchase my sample.

Thoughts

• 6N1P vs 6N3P Based on this limited experiment, I'd say it's more fun with the 6N1P, more rolling old stock possibilities!

• PJ Miaolai This is a pretty good Preamp, but not in the first tier. For its ridiculously low price, it can serve as a good switchboard, with 4 in and 2 out! AND, Headphone Output!

• Douk T8 Pro This is an excellent Preamp! Its Equalizers can even out its own mild deficiencies, and maybe your system's! I'm pretty sure I've not gotten to the bottom of it! For those who run both balanced and RCA, it's even more useful! Highly recommended! A niche product, but one that I heartily endorse.

PJ Miaolai. Engineer David of UMI said this is a poor layout not designed for the best sonic outcome. No matter. I wonder if the 2 Blue Caps are for tube coupling. 1.0uF 100V only.