This review series blows away the high subscriber social influencer/opinion channels (Steve, Thomas) because you actually did the tear-down, myth busting, and measurements. While I may never do a DIY project, I don’t want to add more problematic equipment. Thank you for an education and rational conclusions. I hope you continue your channel and wish you success on KZfaq.

What an amazing series! Honestly I can't believe this type of content is now available. So much better than reading through opinionated threads. Really, I learned so much. Thanks.

Thanks for your efforts put into the series. Your DIY amp looks gorgeous. It seriously makes me consider looking around to find a local DIY group and learn DIY skills like soldering.

Really appreciate you doing this series. I've done all of your mods to my A50 and it really opened up and changed. The clarity on this compared to stock is quite noticeable. I think I've even got less hum/hiss observable when its idling, which probably gives a better noise floor. This little amp really surprised me with how far it can go. It might even be winning compared to a MC275 when using high efficiency speakers, which I was hopeful about but not expecting.

I loved hearing the great explanations you gave in this comparison and the level of detail that we could appreciate. You are wonderful. Your honest no BS approach is refreshing. You are amazing. Great stuff.

I just watched the "whole" series on this amp. Great stuff - I learned a lot. Thank you!

I don’t even do electronics DIY but I watched the whole series. I’ll be waiting for your next videos. Keep it up.

Just phenomenal effort, skills and devotion! Thanks. Now to find someone who can do this for me in Melbourne Australia.

Just incredible! Thank you so much for your videos!!

I just watched the whole series with your new conclusion video this evening. I want to thank you for showing everything & don't need to do some kind of how to guide. I think the videos are complete enough for even a novice like me could do the modifications. You convinced me that the DIY is the way to go to get introduced to 300B. I had a friend who was thinking of getting the Chinese amp but in watching this decided otherwise. I also want to acknowledge you for these videos compared to the other audiophile channels who have praised the A50. They may have big watched numbers but only talk about their impressions about how it sounds but not tests, quality or electronic build. These videos are of such more value for the long haul of purchasing a high quality power amplifier. I get how your passion is to explore new things & not get stuck doing the same mods over & over again. Finally, I like learning about all your tips for DIY like the safety pin trick, etc. I am going to watch your DIY series on the 300B & maybe get up the nerve to build one. Thanks again!

Well, that was fun! You make a lot of great points on why not to buy an amp that needs so many mods.

I have been sleeping through work bc I’ve been absolutely enamored with your videos. I truly appreciate your time and knowledge!! New huge fan !

Thanks for the reminder re: reflected OPT impedances and speaker choices..👍🏼.. Empirical testing is hard to beat in certain situations

If I could give you an award for this series I would...the BEST I have ever seen!!!!!!!

Thanks for a realistic final review

Bravo! I have watched most of the series and learned a lot from you. Most of the asian reviewers on here are lacking when it comes to what a real 300b amp should sound like. Even at a bargain price, evidently not a bargain. Thanks!

I was seriously considering buying this amp, however after your evaluation I have now reconsidered. Thank you for taking the time to share your analysis. I am a new subscriber. BTW..I do agree that your homebrew 300b looks better. Yes, I do like the color of the transformers and the fact that they match your nails is indeed a bonus🙂

I really liked your video. You are honest and it shows! I would do the DIY kit if I had the time. But that does not mean I want to buy the A50… you are right, you get what you pay for, for the most part.

I loved this series of videos...thank you so very much!

Wow I wish I found this channel a little while ago! Really cool content I am going to get one of these DIY tube amp! Cool channel just subscribed!

Like many others I'm so glad I found your channel. I was considering one of the many Chinese amps, and may still buy one, but as you have shown, to get the best from them, mods are unavoidable. I have designed and built passive crossovers for my DIY speakers, so the mods would be no bother to me. When you consider how badly this and other Chinese amps measured out of the box, it makes you wonder what the you tube reviewers are hearing, or more importantly, not hearing. I always take what reviewers and HIFi mags say with a large dose of salt. They need to keep reviewing, so can't be over critical, just hint at issues, and leave the listener or reader to read between the lines. Thanks for all your hard work, and honest opinion.

Thank you for a well reasoned view

love your show. very concise.

Thank you for this series

My mission was looking for tube inspiration to match my loudspeaker project, I've found it right here and now! I sold Hi-Fi for many years and listened to a vast amount of equipment and that was spurred on by my love of music and built my first EL84 class A amplifier pair kits when I was 18. Shortly after we were living in the realms of the transistor and I diverted my attention to the loudspeaker, the weakest link in the audio chain then and now, at present where recordings are better and the medium of tape, vinyl and digital storage systems and amplification has improved dramatically. Since the decades post the 1930s and early amplification using Valves (Tubes), we had no way of knowing how good they actually were or sounded because they have overtaken speaker technology which in principle is a 1930s design, coil, cone and a box, apart from electrostatics and a few novel ideas, nothing has really changed. My design work began in the 1990s when I built my first prototypes using novel techniques for improving drivers and cabinets rather like the improvements we see here in this series of Boyuu A50 modifications and of course the own design and build of the B300 amplifier. When I retired 5 years ago I wanted to try something new. I have all kinds of transistor amplifiers both professional and domestic from a Crown DC300 through a Boulder amp (my all-time favourite transistor amplifier), I decided to try a tube amp so bought a BOYUU A9 EL34 amp kit, changed a few components including tube rolling, connected to my new prototype speakers and it knocked my socks off! I wanted a small single-ended amplifier to drive my unique single point source highly efficient diaphragm speaker with equalised pressure rear and front wave module design in a dispersion vessel with total separation in a slim glass cabinet with isolation pads with a potential of 20Hz with a unit of zero resistance in the diaphragm motion, no suspension and a very easy load on the amplifier. The current grips the coil due to virtually zero resistance and allows the amp to move the coil to where it needs to go and follow the signal path. Thank you for the great videos and reading.

Awesome, thanks!

This is great stuff

And I love the cameo appearances of the dog in the series :-)

I bought this amp several months ago and I love it. Granted, I upgraded the tubes and it has significant use time at this point. I'm using it with some vintage JBL 4412 Studio Monitors at 90db sensitivity and it sounds wonderful. I rarely turn the volume past 10:00 and it has nice room filling sound and good presence. But I have to admit, I kind of regret pulling the trigger now after watching this series. The mods are above my head, not just technically, but time wise as well. I really don't have the patience for this kind of work. Forget about building the DIY version. I'll have to stick with tube rolling and playing with the 4-8 ohm outputs for now. I'll now binge the 300b DIY build as time permits. But I thank you for these videos and also the advice you gave me. Best!

Wow! I've watched so many videos about stereo gear (use to read magazines in the past about this passion of mine for music) now years later I find you! I immediately subscribed in hopes of finding your best advice for a DIY amp to pair with my Klipsch 97db speakers. I have many speakers but after visiting my local Audio Classics store, close to where the McIntosh gear is made, I fell in love with tube sound. Affordability is out of the question and what I loved best was the tube gear used with the Magnepan speakers. You can imagine the power those mono blocks were cranking out. It was definitely out of my reach. So if you can point me in the direction of a DIY project to help my addition I will most appreciate it. I can solder, weld, have a Greelee Punch Set among others. I can paint, fix cars , have access to a break press etc. I'm a jack of all trades and master of none. Presently a journeyman electrician and ready to retire to my dream sound room. Please! hook me up. ^^

Thank you so very much for what you’re bringing to the table. I would love to know how to mod my Reisong A10 SET amp. I enjoy the amp very much, but I did add two 10 inch powered subs with it. I hope it’s something you my consider doing down the road. I love your stuff !!!

Omg gurl love it

Great video as always! I used to hand drill all my chassis. A little Harbor Freight $50 drill press is 1000x better.

Thank you!

This was a great series. Its awesome that you found flaws in the a50 but then fixed and improved it. I have the a10 and I have been thinking of doing most of the caps with better legit brands and while I probably will do them I can only wonder if the a10 has more going on than cheap parts. I will say it sounds great but the bass is its weakest point to me which I have heard plenty of others say the same about the Chinese amps. Thank you,great job, I am looking forward to your next projects.

As an engineer, I’m so impressed with your review video clips which supported by numbers, math, graph on oscillator etc., that are what I expected… I also watched some review of this A50 300B amp by others and they only review by their ears…

Strong statements!! Would be interesting to hear your thoughts on higher priced ChiFi tubes such as the Line Magnetics. Again, you are aware of all the impedance "ups and downs" of speakers. Please, do try to compensate your 600M´s. I have the schematics on my desk. You´ll be positively surprised, promised. Keep up your good work!

I concur with you on the subwoofer idea. But what I’ve been doing for a few years since I got my 4-way Pioneer electronic crossover, is use the low frequency output from the Pioneer to feed solid state amps driving two JBL 15”s. No amp sounds thin since I started with this. On top of that, the mid/high outputs drive tube amps to feed my main speakers. It isn’t budget friendly and complicates the whole system but it gives me huge fun mixing and matching everything. It is the best of everything in one system, not to mention immensely lowered distortion and higher SPL overall. Like the LS3/5A sounds like on steroids giving out louder music, not noise. All in all, like upgrading the whole system but keeping the sound signature of my original speakers.

You are great 👍

yes, thank you very much , quite enlightening. pretty sure a diy is in my future, thanks again!!!!

oh wow..... what an revelation.... like comparing pasta in supermarket freezer and bottle sauce to homemade pasta and sauce...

If you have any female viewers, you could sell Edcor Blue nail polish! Seriously with your DIY 300B amp we know exactly what we're getting.

Thank you for sharing, how can I add another level of pre-amplification to improve the aura?

Posting pictures of the mods you did on your website would help those who want to make them might help. I am building a K88 amp that Blueglow has a video on, just waiting on my transformers and choke to arrive so I can start.

I was looking for a affordable amp project for to long. This channel is the best place I founded to hangout with my newly founded interest in home audio. Being able to benefit from your experience in this "hobby " of yours is just a threat for me. The fabrication part is not a problem for me since it is my new career (Cad and cnc programming) after 24 years of live sound engineering. I also have good friends to help me with the power up and troubleshooting. Question: What would you recommend for speaker load to best fit my fidelity over loudness preference? I'm thinking of going with CR research since, once again, cnc routers are the easy part for me. Love everything about your channel thanks! * I ment GR-Research

A great end to the series! It's been a good journey. Can't do much about small output transformers unfortunately! I'm interested to know... You keep calling your 300B amp a budget build. Parts aside, what circuit mods would you do to make it high end? SRPP driver stage? mu follower? Something else? Or are you happy that the basic cascode circuit is good enough? Not talking about spending more on parts here, just the actual circuit mods you might consider. Appreciate your thoughts.

Quick question about connecting a powered sub... I cant find much info on this but i have seen some comments --- "You need to get a subwoofer with line level or high level speaker inputs; you then connect the subwoofer to the speaker inputs on the back of the amplifier; I recommend REL or HSU for subwoofers with speaker level inputs..."----- I only see right and left speaker inputs on the back of the amp so how would one wire the subwoofer? Sorry as i said i cant find almost anything about how to do this with this specific model (Reisona50). Any advise would be appreciated!

Given the weak bass and the need to up the B+ voltage, would a Solid State rectifier be a reasonable option?

Very nice and helpful. I think you did not mention the value of new coupling caps for 300 tubes. You mentioned that .56 or .47 mf was too large. I assume you went to .33? Is this correct? Thank you

Im looking at pairing this with my wharfedale lintons. Will it have enough “juice” so to speak to operate them?

VU meters... I just like watching them dance! Everything you've said about VU meters is true, but they dance! Think of it like blue nails over red. You just like them because they speak to your soul. RP-600M is a great speaker for the money. Should be priced double or triple what they're selling for. I have the RP-160m which is 99% the SAME speaker. I played the hell out of them for 5 years and was my first decent sounding speakers. I still have them, but I'm probably going to gift them to my cousin, as I've upgraded. After watching your videos for the last few days on the China tube amps, you've talked me into building my own or dishing up the money for a USA made quality tube amp (Decware). I hate to buy something new and only to put more money into it upfront because of shity parts and/or tubes. May as well build. Any thoughts on the Bottlehead Kits? I know some tube amps in this day and age can sound very much like an SS amp. Not what I'm after as I own a SS I'm happy with. Thanks for making videos and guiding me on my tube amp journey.

Thank you so much for such valuable information on the Boyuurange A50. Please forgive my ignorance, but are the modifications you suggested valid for an amp running on 220v? If so, I would very much like to buy a parts kit for the whole upgrade. Is this something that you could provide? Please let me know if this is possible. Whatever your answer may be, thank you very much. You are really helping a lot of people. From Lisbon, Portugal, all the best for you!

Hate to pester you, I do have a question. Your video was about your DIY amp and part cost vs modding the A50 amp plus parts. What would your DIY amp run if you had to pay someone to put something like that together for someone? Parts and labor?

You are very knowledgeable. Way more than me. I have a Beautiful Marantz 2325 , but it’s old and could probably use a restoration , re-cap ect. The wood case everything is so nice , I’m very worried someone will mess it up. Plus I could use the money on a Tube amp? I run a pair of K-Horns up front A, on B I run a pair of Klipsch Belle’s. Together it fills my listening room with live entertainment at around quarter volume. Would Zi be better off with a Tube amp ? The Marantz and Klipsch speakers have been nothing but Quality ! I have noticed that not all tube amps have an A + B ability to play 4- speakers. Could I buy a speaker splitter and run the 4 ? I do run a M&K powered sub , on the K-horns. I’m old and retired, plus disabled so my Stereo gets used and my house sits on 15 acres so I can crank anytime 24x7 with no Police knocking as I use to get when I was young. You are very knowledgeable, I have been thinking maybe Wilkinson 400i . Thank you for your opinion.

Look at those transformers on the amp on the left, that’s quality and no covers like the one on the Right side of the screen. I wonder how big really are the transformers on the Reisong?!!

So would 3.2k be preferable over 5k for a speaker with a 8ohm minimum dip?🤔 Kind of interested in understanding more about the output transformer part with different loads.

Can you switch these Chifi amplifier from 110v to 220v easily?

ola can i simply put 5ar4 direct replacement thank you, good work

Which Mark is the Reisong model? I/II/III?

Some people refer to the 300b tube as the “holy grail” of audio tubes. Do you think this is hype?

I have a l34 amplifier can I switch with it with a 300b or a kt88?

I want to buy your amp.

I'm not an audiophile nor an electronics expert but Vintage equipment usually came with something the new crop of tube amps lack... Tone controls. While looked down on by the audiophiles and maybe people who roll tubes or modify amps, swap speakers to get the perfect sound, wouldn't adding tone controls between the source and the amp accomplish far more and for allot cheaper? A Schiit Loki (4 band equalizer for example is only 150 bucks. change rooms, speakers, etc to me the tone controls just make more sense all around to me. Not a knock on the video, just a thought. have the A10 & A50. the A50 is clearly better. Also have various Klipsch speakers. While the 6" bookshelves you have are ok, I have the RP-160M. My RP-280F's are great with both the A10 & A50 and truth be told once you add speaker stands for the RP-600M's, the $800 a pair RP-280F's (dual 8" woofer tower) just don't take up much more room the the 6" bookshelf speakers & you don't need a subwoofer like you do with the bookshelves. Have a pair of Heresy 2's (ebay find, 7 years ago, 400 bucks for the pair in perfect condition) that shine too but they really benefit with the addition of the Loki as do the RP-160M.

I am nowhere near qualified to make the modifications you demonstrated. You almost make it sound like this amp is basically junk without the mods. Is it possible to enjoy this amp with nothing more than rolling the tubes? Can you at least provide a list of what replacement tubes you recommend without any other modification? Or is it a waste of money buying this amp unless you're an electronics engineer with the skills needed to rebuild it from scratch? I really wanted to get into tube amps as a music lover and thought something like this would be a good start. But now I'm discouraged that anything I can afford is just cheap, overhyped junk and I'm stuck with my overpriced, overhyped Pioneer "Elite" AVR. At least it works and it hasn't blown up yet. I'm kinda upset, but maybe I should thank you for saving me $1,000 bucks along with a lot of grief and stress.

Make no mistake the A50 looks way better. Why does this feel so much like a total promotion video for your product.

I have a 'mark-II' of this amp,--Quite different in design--but similar appearance... 6V6 in triode as drivers, 12AT7 input stage, --And sounds Bloody Awful! Ive had to do full re-design, dumping 6V6 and using 6J5 (half 6SN7) in Mu stage with MOSFET on top, replaced AT with AX and no cathode caps for both. Much better--but still had hum as ground for input stage was routed back to main filter. Moved that ground to the last filter (three B+ filters in mkII) stage, Hum gone. Output transformers same as yours--and are crap! A Square-Wave test at 1KHz at low power is Very revealing..... --Conjunjunctive filter anyone.....?