The Robb Collections

Douk Audio Class A & AB Pure Tube Audio Matching Power Amps & Preamps

October 1, 2025

#522

Gentle reader,

Since I came across a Chinese designed and made all-tube power amplifier at a bargain price on eBay, which I wrote about here: The Robb Collections: World Premiere Review of Douk Audio's Exciting new Class A DJ587 Tube Stereo Power Amplifier! I have continued to be Douk-curious. I updated that article with what I thought was THE matching preamplifier. Turns out, I only knew part of the story.

All Douk Audio images courtesy of Douk Audio.

Well, it turns out there are at least two different ones, both using the same chassis, but with varying numbers and types of tubes. The DJ198 preamplifier is pictured above.

"This!" I'm channeling Doug DeMuro again, above is their DJ417 preamplifier. Note the numbers of and configuration differences. I had come across a DJ918, but it turns out that was a typo as it is "Identical!"* to the DJ198. *remember: My Cousin Vinny

This is identical to the DJ587 power amp which I reviewed and am thoroughly in love with. It is advertised as a "Class A" power amplifier.

And this, is a DJ511. Note the differences between the two of them. The DJ511 is a "Class AB" "Push-Pull" power amplifier.

This is the rear of the DJ198 preamplifier.

And this is the rear of the DJ417 preamplifier.

These are the four tubes which the DJ198 preamplifier uses.

These are the six tubes used in the DJ417 preamplifier.

This is what is inside the factory assembled DJ198 preamplifier.

And this is the insides of the factory assembled DJ417 preamplifier.

The much simpler (looking) Do-It-Yourself version of the DJ198 preamplifier.

And this is the insides of the DIY DJ417 preamplifier.

I am 69 years old and had my first job as a fledgling auto mechanic in 1973. My father had a Hallicrafters multi-band tube radio when we were growing up, just like this one. IT was my first experience with tube audio equipment. I was allowed to take it to work so that I had music. IT received AM only, WGOE was my rock station. What I knew about tubes then: It takes a while to "warm up" to make sound. And, do not stick your fingers or anything else inside the back of the radio. That was it.

This was Nancy's father's actual Hallicrafters multi-band tube radio. It still worked when we were dating in the early 1990's. Nancy inherited it. I have not tried to see if it still works. It might.

This is a Hallicrafters Civic Patrol radio I found in an antiques store and bought. It does nothing but buzz. Maybe the frequencies are no longer used. I do not know.

This dangerous and I-do-not-even-want-to-try-and-see-if-it-works, Philco radio I bought for five bucks, also from an antiques store.

These are is it's guts after I cleaned them up and put them back inside.

This is an identical, but slightly older Philco I bought via eBay for ten bucks. It is in surprisingly good condition and has the proper factory knobs.

When it arrived, the back cover had been shoved in a bit during it's trip to our house. I removed it to fix the cover. I found everything clean and shiny inside, much to my delight. As you can see by the tube's glow, it works. It's AM only, but it's from 1937 and it WORKS!

What I have learned about tubes since then is: Tubes operate at high voltages, thus the three transformers verses one, the AC power transformer, in solid state equipment.

This is the back of the DJ511 power amplifier. Note a single input.

This is the back, identical to my DJ587, power amplifier with two swtiched inputs.

The insides of the factory assembled DJ511 power amplifier.

This is the eBay photo of a DJ587 which was in the eBay ad for the one I bought. I have not taken the bottom cover off to see what may be much different (based upon every other unit in the series) that what this photo shows. Perhaps more like the other factory assembled units shown above.

Note: All of these new product images were made by Douk Audio employees in China. I secured all of them from their eBay product ads on eBay. The vintage equipment (minus the first Hallicrafters photo) were made by me.

Now, that you have the model numbers of the two preamplifiers and two power amplifiers they have produced so far, with this chassis. I look forward to reading your comments regarding the differences between the two sets of fraternal twins. For instance, which of the two designs is better.

One last thing, if you are a tube aficionado, what benefits could one expect by using NOS tubes or Soviet ones compared to the modern day Chinese made ones?

Thanks for taking the time to read this, the second chapter, of my new interest in tube driven stereo equipment. Feel free to leave a comment below, or via Facebook.

I write two more blogs, but have not updated either in a while: Pictures of Nancy. The Love of My Life. and: People Say I'm Special. But I Don't Know Why

Scott Robb

October 1, 2025

#522

Michael Slayter, One of America's Hidden Literary Genius' His Three Books are EPIC!

September 30, 2025

#521

Gentle reader,

Most of you know me for writing about our many collections over the years. There are still some I haven't covered, such as Nancy's vintage clocks collection. This article is going to be different.

One never knows what the future holds for you. I certainly had NO idea how our lives and mine in particular would change so massively and positively as it had since 2021 when a little voice said to me, "It's time to go to church."

I honestly state: These three books are some of the FINEST that I have ever read.

Now, please stick with me. This article is not about that "little voice", it is about my friend, Mike Slayter, who is also our church's Parish Assistant. He grew up in Louisiana and decided that he wanted to be a Veterinarian. He joined the United States Air Force as a Veterinarian. Yes, the US Military employs just about every type of job one could get in the "real world"* and they do have animals. Dogs in almost every land-based branch and horses in the Army.

*The term "real world" came about during the Vietnam war, particularly with draftees. Since that country was so very foreign to them in so many ways, they felt like they were in another world.

Our parents read to all five of us from a very early age. In my case, I read to all four of my kids. All of them are also avid readers. The two which have kids also read to their kids. As a result all of us (siblings) are still avid readers. Mom loved Kindles and gave each of us one. I gave mine to my daughter. I am a physical media person. I like real books and other real things I can hold in my hands. We still have and can watch or listen to: VHS video tapes, cassette audio tapes as well as records, CDs and DVDs. Fortunately, player makers made sure that Blu-ray players can also play other formats which use the same size and types of discs.

As an avid reader, I read whenever and wherever possible. My last career had much down time, especially in the Winter. That being said, if there was nothing for us to do, I'd go somewhere and read. As a result, in my 69 years on this planet, I have read thousands of books and countless magazines. I have owned many hundreds of books and in fact, have built shelves to hold them. The image below is from 2008. Almost all of those books have gone to live with other folks. It is only one of the many bookshelves in our humble home.

Getting back to Michael Slayter, he was just another man in the congregation of First United Presbyterian Church of our town when I met him. Over time, we got to know each other. He is not one to blow his own horn. His capabilities have be sprung on us from time to time. The first we knew about his being a "Commissioned Pastor" was when he was preaching one Sunday instead of Pastor Adam. The first we knew about him being a published author was when he posted a photo of his book A Journey to Understanding, on Facebook, which his about his unlikely journey from being a retired US military Veterinarian (a Veteran Veterinarian!) to becoming a commissioned pastor. I had never heard of "commissioned" pastors before. Always one to support my friend's interests, I bought the book from Amazon, read it, learned a lot more about Mike and thoroughly enjoyed it. In the case of this book, every dollar earned by it's sales is donated to our church. Amazing and humbling.

The first I heard about him writing FICTION was, again, when he posted a photo of his latest book on Facebook. I said out loud, "He writes fiction?!" and jumped onto Amazon to see his books. He is self published, which means he paid to have his books published. That costs a lot of money. It is one way to get your books out there rather that trying to get publishers to buy your story and publish it.
A smart first time author will write under a pseudonym or "pen name". That way, if the book fails, their reputation is still good. Thus, Kisatchie Voices was "written" by J.C. Oliver. Each books is totally unique. Each is in a different location with unique characters. The tie that binds them is that Mike lived in all of the locations in which they take place. Thus, his descriptions are based upon actual knowledge and experience.

Mike has the ability to write from a child's perspective, a female perspective and about things he never experienced, but that are so REAL, that I swear he MUST have experienced it! His literary style is just wonderful. Many times I would stop reading and say, "Nancy, listen to this line Mike wrote." and read it to her.

Rather than tell you about each story, let's treat this as if you found each book in a store.

And the latest, which I just finished reading last night:

I absolutely love Mike's writing style. Remember I have read thousands of books, including entire collections from authors such as J.R.R. Tolkien, W.E.B Griffin (and earlier books under his own name William E. Butterworth), Tom Clancy, Michael Connelly, J.A. Jance, Ken Follet, David Baldacci and so many more. I've spent a lot of money buying books. Most of them, I donated afterwards. I think I have made my bona fides clear: I have read many excellent authors and do know what great writing is. Here is a photo of him from our church directory.

Out of wanting to protect his privacy, I am not going to give you any more information than the book's back covers do.

I WILL tell you this: If you buy and read any of his four books, you WILL be moved emotionally. You will be glad that you did read that book. And, if you are like me, you will want to buy read more of his books. I can't wait for the next one to come out, especially the fiction books. I was so immersed in the stories, I was that little girl, I was those two brothers and I was Cash, the main character of his latest. There were times that I cried, especially near the end of The Heard Doesn't Ask. That particular scene hit me so hard, it helped me to deal with buried emotions about my own mother.

His writing covers so many events which happen to the characters. Some which seem to come completely out of nowhere, but which help to explain why that particular character is acting the way they are. I repeat: These three books are some of the FINEST that I have ever read. Help me get the word out about Mike's books. They are available only via Amazon's web site. Search: Michael Slayter Books. Kisatchie Voices is currently out of print. But, if enough people look for it, they way print more.

Remember: I do not get paid in ANY way for writing this blog. It is a labor of love and I enjoy writing it. Mike does not know that I wrote this. He will find out the same way you did.

Thank you so much for taking the time to read this article. I pray that you will consider buying at least one of his books. Again, he does not know that I am writing this. I do so out of love and respect for Mike. I greatly admire him. Oh, one cool thing about Mike: He drives a little sports car with a manual transmission. A man after my own heart.
These are what I drive. Both were bought used. The one on the left is a 2013 Cadillac ATS Performance 2.0T. The wagon is a 2005 Volvo V50 T5. Both are performance models, both have turbocharged engines and six-speed manual transmissions. And, though one would not guess by looking at them, they both have official top speeds of 149 MPH.

I write two other blogs: Pictures of Nancy. The Love of My Life. and People Say I'm Special. But I Don't Know Why I have not updated either of them lately and need to get back to them. Mike has inspired me and does not yet know it.

Feel free to leave a comment below or via Facebook.

Scott Robb

September 30, 2025

#521

World Premiere Review of Douk Audio's Exciting new Class A DJ587 Tube Stereo Power Amplifier!

September 26, 2025

Updated with new information September 27, 2025

#520

Gentle reader,

I am very excited to be the very first person to review Douk Audio's new DJ587 Tube Stereo Power Amplifier. To my knowledge it is their very first tubes-only power amplifier and I am delighted to have one and to be able to tell you all about it!

To research this article, obviously I looked for any and all information about the DJ587. What did I find? Absolutely nothing! Their eBay auction does show specifications for the amp, but, the amplifier itself is devoid of any markings or labels of any kind. Were it not for the schematic which they included, I would not know what goes where into and out of the amp. It seems like they rushed it to market to see if anyone buys them and then will market them more effectively.

The DJ587 is being sold via eBay by Douk Audio's subsidiary Nobsound. It is available in both KIT form and fully assembled. Since it has been fifty years since I built my very first real piece of stereo equipment in kit form, a Dynaco PAT-5 preamp, and I have never built anything which uses tubes instead of transistors, I chose to pay a bit more to get it factory assembled. Below are the photos Douk Audio uses in their eBay auctions for the DJ587 Tube Power Amplifier:
This and the following six images are courtesy of Douk Audio.

As you can see, compared to 20th Century tube power amplifiers, it is very sparse beneath the top cover.

Also, were it not for me saving these images, I would not have know which of the three larger tubes went where.

Since I have been a solid-state (transistors, not tubes) equipment person since the beginning, the only other tube equipment I have tried out is an Aimiya T2 as a tube buffer. I wrote about it here: The Robb Collections: Review of AIYIMA T2 6K4 Tube Preamplifier Can this Solid Little Asian Beauty Sing?

To make sure that it still works, I connected it between my B&K Components PRO10 preamplifier and it's matching ST1400 power amplifier. Sort of as a "tube buffer". It worked fine, so, my next step in this review was connecting my SONY CAR Discman CD player to the T2 and the T2 to the DJ587. Why? So that I would have the most tube-only path from the source to the speakers in order to try and tell if there anything to the "Tube Warmth" others have spoken of.

The AIYIMA T2 from above. I could do without the blue LEDs. Red cover is over the Bluetooth antenna connector.
As I mentioned above, the lack of markings or labels was solved by the schematic. Tube powered equipment, back in the day, had up to three choices of speaker terminals for speakers with: 4, 8 or 16 Ohms impedance.
Pardon the glare. It is from the LED light above the record shelf. The DJ587 sits atop my ST1400 transistor power amplifier.
While not obvious, a close look (by clicking or tapping the image) will reveal that all seven tubes are glowing orange.
The only vintage equipment I still enjoy are the 1976 Dynaco A25XL speakers. I could not find any specifications until I found: Audio Database which lists a sound pressure level (1 watt @ 1 meter in an anechoic chamber) of 19 dB. The same as my Cerwin-Vega! LS-12 speakers. Interestingly, the site lists the A25XLs frequency response of 30Hz to 20kHz. C-V states the LS-12s as 29Hz to 26kHz. So, at least on paper, they are virtually identical speakers despite SO many differences.
The reason I bring up the speakers sensitivity is this: The title of the eBay page is: HiFi Single-ended Class A Tube Amplifier Stereo Audio Power Amp for Home Speaker The description of the amp, taken directly from their eBay page is this:

"Warm tips

1. DIY KIT version (without power cord) requires some welding ability to solder, and we do not provide step-by-step guidance. Otherwise, please consider purchasing the finished version (with power cord).

2. Due to the scarcity of vacuum tubes and the instability of inventory, the actual shipment will be replaced with different types of tubes and components according to the actual situation. All replacement is of the same level, and there is no difference in function and effect.

Features
Reasonable tube design: choosing 6N2 and 6P1 vacuum tubes to amplify the signal and power, and 6Z4 as rectifier tube. Each tube has been tested to ensure good performance. Pluggable tube design provides much more playability.
Pure audio experience: adopting single-ended circuit, working status remains class A and output power is 4W+4W. Superior sound quality, and excellent transient response, providing a premium audio experience with reliability and efficiency.
Exquisite craftsmanship: Handcrafted point-to-point wiring ensures superior sound quality, customization, and a unique aesthetic appeal, making it an ideal choice for audiophiles seeking the best listening experience.
Stylish enclosure design: boasting a brushed stainless steel chassis for durability and a galvanized iron plate baseboard with CNC-punched rectangular holes for optimal heat dissipation, ensures both style and performance.
Warm tips

1. DIY KIT version (without power cord) requires some welding ability to solder, and we do not provide step-by-step guidance. Otherwise, please consider purchasing the finished version (with power cord).
2. Due to the scarcity of vacuum tubes and the instability of inventory, the actual shipment will be replaced with different types of tubes and components according to the actual situation. All replacement is of the same level, and there is no difference in function and effect.
Features
Reasonable tube design: choosing 6N2 and 6P1 vacuum tubes to amplify the signal and power, and 6Z4 as rectifier tube. Each tube has been tested to ensure good performance. Pluggable tube design provides much more playability.
Pure audio experience: adopting single-ended circuit, working status remains class A and output power is 4W+4W. Superior sound quality, and excellent transient response, providing a premium audio experience with reliability and efficiency.
Exquisite craftsmanship: Handcrafted point-to-point wiring ensures superior sound quality, customization, and a unique aesthetic appeal, making it an ideal choice for audiophiles seeking the best listening experience.
Stylish enclosure design: boasting a brushed stainless steel chassis for durability and a galvanized iron plate baseboard with CNC-punched rectangular holes for optimal heat dissipation, ensures both style and performance.
Parameters
Audio input: Stereo RCA
Audio output: Banana speaker jacks
Output power: 4W*2
Suitable speakers sensitivity: ＞90dB
Frequency response: 20Hz-20KHz
Input voltage: 100-120V / 220V-240V, 50HZ/60HZ
Main transformer power: 75W
Output impedence:4Ω / 8Ω
Power transformer: 76*50
Output transformer: 5k, 66*32, 8W
Dimensions: 328*176*52mm / 12.9*6.92*2.04in
Net weight: 4.5kg / 9.92lb
Package weight: 5.5kg / 12.12lb
Packing List
1*DIY Kit / Finished version (optional)
1*Power cord (only for finished version)

That's right, you did read FOUR WATTS per channel. Also, "Class A" is THE best sounding of amplifier specifications and very hard to achieve.

To be frank, since there was ZERO information on the Internet, including Douk Audio's OWN website about the DJ587, I was almost afraid that it was a cleverly done scam and I would receive nothing. To my delight, this box wrapped completely in brown plastic tape (like illegal drugs I have seen on TV) did arrive five days after I paid for it. It traveled by truck from Los Angeles to Virginia.

I have photographed the entire brochure, which is thick paper with sleek plastic covering, to show you what it has inside. On close observation, the amp IS in it, but simply labeled as: DIY KIT on page 05.

I have already removed some of the soft Styrofoam packaging at this point.

So far, so good. Three transformers. The left one converts house current ("mains" for my UK readers) to the voltage the amplifier needs. The other two convert the high voltage tubes use down to what speakers can handle, which is not a lot.
The transformers are the bulk of the weight. Note, no markings of any kind. Anywhere.
Two pair of RCA inputs, which is nice and in my experience, unusual. Again, thanks to the schematic and LACK of labels, I knew to use the outer red speaker terminals for my 8 Ohm speakers. Note IEC power socket so that one can use quality power cables.
Nicely finished and perforated steel bottom cover and sturdy feet. The unit is surprisingly heavy for it's size. A mark of quality. The heavier the transformer, the higher the speaker output power.
The tubes safely wrapped in bubble wrap and what is actually yellow tape. The brown box makes it appear brown.
Once again, thanks to the eBay web page, I knew which socket the shorter fatter tube was designed for. Another "interesting quirk and feature" I'm channeling Doug Demuro here, is a volume knob.
An overhead shot without all the glare. My Lumix LX7 digital camera has a fast Leica lens with a maximum aperture of f1.4, which makes this shot possible without flash.
A full sized scan of the included schematic of the amplifier. A buddy pointed out that Douk Audio chose to use a tube to rectify the amplifier. I have no idea what that means. I was not a tube person. But, I sure AM now!
I have made these two brochure photos large to make it easier to see all of their many products.
Now, I want to make one thing perfectly clear: I do NOT get paid by anyone to write reviews. I BUY the products at full price and review them as the OWNER of the product.

With that being said, here are my thoughts on this new Douk Audio Class A DJ587 4wpc Tube power amplifier: IF you have quality high sensitivity (the higher the dB number the speaker manufacturer supplies) 90dB or greater, you WILL be happy with the sound of this amazing little amplifier. I am sold on tubes now. It took me fifty years, but I finally get it!
Now, have patience with me, as far as the quality of the video. First of all, I am new to smart phones. Thus, it looks like there was an earthquake happening when I made the video. Secondly, my phone, since I am new to them is one made for seniors. That being said, this video is for informational purposes only.

If I had room for a real Tube preamplifier, the AIYIMA T2 is more of a novelty than a serious preamplifier, I would be in the market for one.
This is a photo I shot, with a 10mm lens on my Nikon D300 DSLR camera, of the listening room. First off, I am not a "gun lover" or a hunter. I am the opposite of that! The rifle does not work. It is missing it's firing pin and the maker went out of business a LONG time ago. Secondly, the Jackelope is a fictitious animal, my ever-loving wife bought it for me. Thirdly, the cat skin was purchased by a dear friend many years before I met him in Thailand. It is from a Fishing Cat. Yes, there are such animals, look it up. If you look closely, you can see my B&K ST1400 power amplifier in front of the record shelf.
This is a photo of my stereo system. I have been in this hobby since 1975. Yes, for fifty years. I know what sounds good and what does not. I can unequivocally say that Douk Audio's DJ587 Class A Tube Power amplifier, through my Dynaco A25XL high-efficiency speakers sounds FANTASTIC! No ifs, ands or buts. I LOVE the way this low powered simple beauty looks and sounds. I have yet to detect ANY distortion at all. NONE.

I do know that the brands of tubes can make a huge difference in the sound. I am fearful that I may fall down the tube equipment rabbit hole because I just found out that they make a matching PREAMP!
As you can see, it is the same chassis and has the same lack of labels.

AS does the rear lack any labels.

Reading the mixed reviews on Amazon, several experienced tube equipment owners have stated that replacing the Chinese tubes with "better" ones makes a huge difference in the preamp's sound. I keep silently saying, "I do not need another preamp. I do not have room for another preamp."

So, does that mean that I recommend that everyone who wants to see what this resurgence of antiquated Tube audio equipment is all about fork over their $219 USD and get one too? No, it does not. I think I have made it clear: You MUST have high efficiency speakers which have a tested efficiency of 90dB or higher. Otherwise, you WILL be disappointed. You have been warned.

To conclude: IF you DO have high efficiency speakers AND you and your family will not suffer because, "Scott Robb raved about this inexpensive tube amplifier and I just HAVE to get one!" Then, by all means, order one. Heck, if you have experience soldering, buy the kit and save a few dollars.

Thank you for taking the time to read my article on this miraculous little (and heavy) tube power amplifier. Again, I do this for FREE, no one pays me anything to write. Feel free to leave a comment below or via Facebook.

I write two other blogs, but have not worked on either for a while. I need to get back to them. Pictures of Nancy. The Love of My Life. And: People Say I'm Special. But I Don't Know Why

Scott Robb

September 26, 2025

#520

PS Every Robb Collections article is available. Just keep scrolling down and down and down after this sentence. At least they are on a PC.