REVIEW: Meng Yayi KT88 Monoblocks

Meng Yayi Mini KT88 Monoblocks review (quite long)

It's easy to find reviews of expensive amps but rarely do we find reviews of (extremely) affordable ones. Let alone from direct-to-consumer, over the internet, Chinese made amps. So I thought I would indulge here with a review of the Meng Yayi KT88 monoblocks. I have come across many audiophiles in chat groups asking about them, but no one to actually answer. At about $650 for a pair, including shipping no less, they are a rare steal. The question everyone asks is "can a cheap Chinese amp be any good?". Well, I ordered 5 of these monoblocks (yes, 5) and played with them for about a year and a half now. I used them in many applications: as the centerpiece of my main stereo system for music listening; in a full 5.1 Home Theater set-up (hence the 5 monoblocks); and also as a 10 hour/day work office set-up. In the process I experienced break downs and set backs; but let's start at the beginning.

Ordering the amps was easy - they are available on ebay and through a few other websites, including where, 18 months ago, I ordered a first set of two. I had a few questions ahead of ordering and they were quick and responsive - if in broken english, which is no problem. Within a few days I received an email with plenty of pictures of the amps being packaged and the labels taped on the boxes, including close-ups of the labels with tracking numbers. I was impressed. I have never seen such thoughtfulness from any manufacturers in my life. Sure enough, the tracking registered right away and 6 days later the amps were delivered by DHL to my place, in perfect condition.

Inside the boxes were the amps, fairly well protected (no damage), plus all the tubes in small nondescript white boxes with bubble wrap. Obviously no brand name tubes here, but all was fine. I can't say that I was impressed with the workmanship of the amp though - but I wasn't expecting otherwise, not at this price anyway. The wood trim is held in place with glue (the hot glue kind), with beading squeezing out at the extremities probably while the piece was pushed in place. A quick work with the Xacto knife cleaned this up easily enough. The printing on the amps looks amateurish, but once again, what did I expect? The amps are heavy (no lightweight transformers in there) with no loose parts, which is what counts at this point. Like I said the tubes are truly generic, with inconsistencies that are worrisome on the surface: for example the 6J4P tubes are quite different on both amps. Although they are from the same manufacturer (from the graphics and codes), they are obviously different - one is taller than the other and the bases are of different silver hues. Would this influence the sound? I wondered.

All the tubes went easily in place and the sockets were straight (I hate having an amp where tubes are slanting like the Pisa tower - these were all standing tall and straight).

I plugged the amps in my stereo system, feeding from a vintage Marantz tube preamp to a pair of Acoustic Zen Adagio speakers. The Meng Yayi monoblocks have two gold plated (is it really gold?) input ports, labeled "CD" & "AUX". The CD input turns the monoblocks into an integrated amp of sort, which means that the volume is controlled by the pots at the front. I say "integrated amp of sort" because it is beyond me why one would use monoblocks in that fashion. Controlling the volume that way means turning the pots from each monoblocks in perfect unison to keep the balance from left to right. On the other hand using the "AUX" input bypasses the volume pot and turns these amps into true mono amplifiers. It is a good thing as the pots are of very dubious quality: they do not feel smooth or nice at all to turn. Better to bypass them, have a simpler signal path, and be done with it.

The Mini Yayi KT88 monoblocks are the most powerful tube amps that I personally owned so far; and at a rating of 50 watts each they are much more than my Acoustic Zen speakers require to shake the house. During all my listening I never really cranked the volume much more than half. But what I was happy about was that right at the onset the sound was miles ahead of any solid state amps I ever used with the Adagios. It is no secret that Acoustic Zen speakers react well to tubes (Robert Lee from Acoustic Zen will say so himself), and my experience supports it wholeheartedly. Where the speakers were previously lackluster, suddenly the level of depth bloomed in the music. I was expecting this as my small 8 watt integrated (6L6 tubes) is driving the speakers to a similar effect, albeit with a lack of power.

I made a conscious decision to give the Meng Yayi KT88 monoblocks some serious hours of play time before starting to truly listen to them - as from the onset there was a possible cloud over the horizon. There was a hum generated in the speakers, at the same frequency as the hum emanating from the transformers in the amps. To hear the hum from the amps I had to keep my ear close by - at about10-12 inches or so. The hum in the speaker drivers could be heard from about 2-3 feet away. It's not much, but enough to be worrisome. Of course it was unnoticeable when any kind of music was playing, but knowing it was not the best feeling. A letter to the company yielded 2 things: a suggestion to buy a power conditioner for the electrical input; and to wait until the units had some more burn-in time to settle things down. I quickly decided against buying a new power conditioner as I never had such a problem in the past - it didn't make much sense that this may be the problem this time around. But I decided to wait as it is a fact that some vacuum tubes are noisy when new until they settle down. So any serious listening test was put on hold.

Alas, a more serious hiccup happened. About 2 weeks after having the amps one of them ceased to work. It would power up but no signal would come out. This is where all the warnings one can hear over the internet came back rushing: buying overseas makes repairs a real pain in the cheeks. Sending the Meng Yayi back would have costed me a fair amount of money, plus the waiting time involved. Instead I decided to bring the faulty unit to a local tube amp repair shop in San Francisco. A few days later I picked up the amp, paid the $95 for the repair (a few resistors failed, they said, and replaced them with better ones), and brought it home. As soon as I plugged it a loud *pow* signaled an explosion and thick black smoke came out billowing from the side vents. Great. I turned it off right away and took it right back to the repair shop, dreading that this was the real end of the unit. So maybe they said that they repaired with better parts, but I learned a lesson about the better workmanship in America over China: it means little. The repair was worse than the original workmanship. At any rate another week passed and I got the amp back. They would not say what went wrong, and there was no fee for the second repair. This time the amp worked fine.

One would say that I would have learned better, but I was wondering still: could this just have been a fluke? I wrote to Meng Yayi again and told them the story, and also told them I wanted 3 more units (my goal was to try this in a home theater system). They apologized for my bad experience and said they'd send some nice interconnects for free with the shipment of the new amps. The same shipping process as above happened (and still impressed me) and a week later I had 3 more Meng Yayi KT88 monoblocks. But no interconnects. Further efforts proved futile: I would never received the interconnects. One can see here the limit of customer service with an oversea supplier. There isn't much leverage. But in the meanwhile I was starting to play with 5 monoblocks.

Right of the bat, one didn't work. A few minutes of detective work pointed out towards the blown power fuse. The Meng Yayis come with spare ones, so all it took is a minute to change it. No problem. One of the amp had something strange though: the AUX input and CD input were reversed. Although I was flummoxed at first, once I discovered the problem it proved to be an easy fix as well - all I had to do was to switched the cables to the other input sockets. Nevertheless there's a real cautionary tale here: if the installation/soldering of such parts can be overlooked at the manufacture, what does it say of the rest of the circuit and how it's built? While I didn't find any other problem from there on, it makes one wonder - and can be a hit or miss like I experienced.

Score so far on 5 amps: 1 major break down, 1 serious mishaps (reversed input ports) and 1 minor problem (fuse). I need to admit, not exactly stellar. But what about the sound - isn't it what it's all about?

I used two monoblocks in my stereo system for about a month and listened to music every day. The hum subsided slightly, but not completely. These are not what I would call "dead quiet amps". In all honesty, though, I love the sound. Three dimensional is the adjective that comes to mind. The voices are particularly luscious and float apart from the music. The impression of dimension, or volume in space, is intoxicating. So much so that I wanted more. The highs were at first slightly bright but subsided quickly to a great balance after a couple of weeks of listening. The bass is adequately deep and rich but very far from boomy - in fact I know that the Adagio speakers are capable of much more oompf in the low end than what the amps were driving. The Sigur Ros Hvarf Heim album is quite a test: the piano solo at the beginning is absolutely breathtaking, but when the bass starts billowing the sound gets compacted and starts losing punch. Could it be better? Of course, it isn't hard to imagine. Did I enjoy the music anyway? Absolutely.

Next I installed all 5 amps in a home theater set-up (the lone unit for the center channel). I will not bother you too much with the details, as ultimately the experience was a fiasco. Multiple factors contributed to the disbanding, but the 2 major culprits were the aforementioned hum and the hopelessness of the A/V processor I used. The hum first: on a two channel system, listening to music from 8 feet away it is not much of an issue. For a HT system with 5 speakers humming, some near your ears, it becomes an issue. During some dead quiet moments in a movie one can concentrate on the speakers and hear it. I am not sure if any of my guests ever noticed it, but I knew it was there and it was enough. The second problem is irrelevant to the amps but contributed just as much (if not more) in stopping the experiment: the A/V processor, an Emotiva UMC-1, was a hopeless piece of electronics that went back to the manufacturer 4 times for repair (the 4th times it was replaced with another, used, unit) - all to no avail. I ended up getting rid of it, which ended the experiment of using the Meng Yayi KT-88 as HT monoblock amplifiers. Of note: even with all the monoblocks turned off (or even disconnected), the Emotiva unit transmitted as a direct line its own hum to the speakers! I have no doubt that this contribution made the whole setup a fiasco. Here's what I learned: Emotiva may be an American company, but when it came to repair its own unit the experience was as hopeless as the idea of sending a monoblock back to China for repair.

After that I took 2 monoblocks to work where they replaced an aging Fatman iTube. I connected them to two Wharfedale Evo2-10, and drove the music from the iMac computer. Right away the increased power over the 13 watts of the Fatman made itself felt. The music became instantly more vibrant and luscious. An interesting side effect happened: while the sound on the Adagios has a crispy clear high range, extremely dynamic and detailed - the bottom end always feels lacking. But on the Evo2-10 it is never the case. The bass is well driven and very clear - even deep - but the highs are more muddled. Obviously I already know that the Wharfedale speakers have a wonderful mid-range sound that I like (it is why I chose them for my work place, as I listen to them nearly 10 hours a day and the sound is never fatiguing). The tweeters are not as efficient as the ribbon tweeters on the Adagios, so that explains that. But why the increased bass befuddled me: where did it come from? After all the Evo2-10 are smallish monitor speakers and surely can't match the Acoustic Zen deep bass reflex. It struck me that the only differences are in the sensitivity of the speaker drivers and the noise level of the environment. My house is eerily quiet at night while my office has a constant noise level from anything and everything. As such the two Yayi monoblocks in my office are nearly always driven between 35% to 60% of maximum power; while the house monoblocks rarely go over 20%.

So I tried something: I stayed late at work one night, waited until the world went quiet, then lowered the volume to a power level closer to my home average. Ah-ha! Somewhere around 25% and below the bass suddenly begins fading away and losing its punch. The bass started feeling flat and anemic: but all is relative - it was still much better than what the poor Fatman iTube was previously doing. I did the reverse experiment at home, which was somewhat painful to my ears: I increased the volume and kept an eye to the bass. Sure enough the depth of the bass and its definition increased as the volume climbed. Except that I would never want to listen to music at that level.

It seems that the built configuration of the Meng Yayi KT88 monoblocks asks for them to be run hard in order to deliver the full range without an unwanted drop in the bass frequencies. I am now considering adding a subwoofer to the stereo system in order to shore up the bass at lower volume.

I ran into a great write up the other night (on 6moonsaudio) about tube rolling, and the sonic difference between tubes. Here's an excerpt from the article (found at - excerpt is pulled from page 2):
"Sonically the classics (vacuum tubes) are more fluid, midrange-centric, burnished and opulent as well as bandwidth-limited and dynamically less potent. The moderns have wider bandwidth and stronger bass. They sound more linear and controlled/damped. In trade they give up some ne sais quoi of the classics. It would be astute to say that for classical music, the classic tubes are more compelling for their greater succulence and fleshiness in the timbre domain. For hard-hitting bass-potent modern fare, the tauter more robust and dynamically stouter but also drier moderns would seem more appropriate. Needless to say, none of this factors listener preference. Nor does it the very real influence of driver tubes which often exert more control over the final sound than the designer output glass."

What it may possibly mean is that the Meng Yayi monoblocks could possibly live up to a fuller potential with sonically better tubes. Maybe there's more to discover yet with different tubes than the very cheap original ones - maybe to the point of correcting some if not most of the lacking.

Now back to the hum. Guess what, it (nearly) completely disappeared from the units at work. They have been playing for nearly six months now, 8 to 10 hours a day. I didn't notice at which point the hum subsided but the amps have well over 1000 hours of play in them. The amps at home still have a slight hum, but they have maybe 300 hours of play so far. That and the fact that the Acoustic Zen speakers are much more revealing of such flaws.

Ah - a last detail: one of the blue LED that lights the middle vacuum tube (for mood only) burned off in one of the amps at work. Once again, no big deal but it does bring the whole quality issue at the forefront once again.

In a nutshell, the verdict: the sound is warm and luscious. The midrange is very forward, clear, well defined and never sharp. It's a "big" sound in the classical sense and very dimensional, human and perfect for vocal; but much less so for hard rock or metal. This is what this amp is good at: the midrange warmth and touch. The bass is lacking unless you like to crank up the volume; the highs require a fast ribbon tweeter in your speakers to make them soar. I like to think of these monoblocks as delivering a sound shaped like a bell curve: all the power and detailing is in the middle, the more it strays form it the flatter it gets. Cranking up the volume adds power to the ends and somehow flattens the curve, giving you more bass details and treble dynamic. Would I buy these amps again? Honestly, probably not - not with the number of problems I had with them. Yet I will keep them longer and start rolling tubes. That whole world remains to be explored.

As a more generic question, would I buy another Chinese amp again, knowing what I now know? Most probably yes. Truth is, the Meng Yayis are incredibly cheap for monoblocks with KT88 tubes, so I couldn't expect too much to start with - and yet the sound itself isn't half-ass bad. In fact it is quite soothing. Could a slightly more expensive, better built amp bridge up the shortcomings of the Meng Yayi KT88 monoblocks? I would like to think so. Let's be honest here, a huge number of better known western brands have their amps built in China. They are perfectly fine and trusted upon. They are not better because they are more expensive - the are more expensive because the brand name is added on top, along with the distribution network and retailer profit. They are better because there is a known quality control happening, and hopefully a well designed circuit. But they are still made in China. In other words better amps can be found (and are made) in China. The Meng yayi may not be the panacea, or even the best example, but I believe that somewhere there's the right source waiting to send me a great amp - not just an okay one. Which brings me to...:

Big surprise, I am now toying with the idea of getting another tube amp from, where else, China. I'd like to replace the Fatman that has now moved in my bedroom (driving two Wharfedale Diamond 10.7). That would be another fun experiment to do! I'm wondering where my searches will take me...

Serge McKig
Berkeley, California

Thanks for taking the time to write this detailed account. Product quality and reliability remains a challenge for some chinese products and then there is that terrible feeling of isolation when thing do go wrong...
Wow, now that’s what I call a write up, very detailed. I purchased a Music Angel XD-SE KT88 about 6 years ago, just now starting to use it, I rolled in some JJ Electric Blue Glass tubes on it. This is my 2nd Tube amp, my first being another Chinese 6J31P headphone amp which I love. But the Music Angel is so nice sounding, I just have a solid state Samsung SACD player connected to it, this amp is a beast, I barley turn the volume up and it's already loud. I noticed the longer the amp stays on gets warm, I've noticed the music becomes livelier and more detailed. I haven't really upgraded the RCA cables or speaker wire to anything really expensive, but it's already sounding good to my 40 year old ears. But so far, I love my purchase on this amp.
Kiwi_1282001: I believe that you are dead on right: when things go wrong with a product bought oversea the feeling is quite depressing. I would not suggest anyone to get a similar amp (aka bought outside the country) unless one is ready to accept the burden for fixing it if it goes wrong (as my experience shows, things can indeed go wrong).

Mark916: Thanks for the nice words. The review was fun to write! I believe that the Music Angel would probably have given me a wee bit less trouble (one step up the ladder, so to speak!), but truth be told I enjoyed the challenge and the experience. I am starting tube rolling as well (jumping quite high off the bat with some incoming TJ Full Music tubes). We'll see what comes out of it.

BTW, just like you I noticed that the sound improves as the units get warmer. Richer, fuller, warmer - all good words. But also deeper in the bass and much faster attack and more natural decay. Thing is, this is not unusual for tube amplifiers. Except that the Meng Yayi KT88s take about 45 minutes to 1 hour to get there. Interesting...

Cheers all,

Sounds like you rolled the dice purchasing these and amps and happy to hear things worked out for you. I owned a Cayin TA-30 that sounded pretty good and was relatively happy with but I'm aware that Cayin has a U.S. distributor and it's not really the same but nevertheless it is a Chinese product.
That being said I would never order an amp direct from China after hearing my custom built kt88 amp from Jim Nicholls at JWN amps. It is rated at 40-50 wpc but man does this thing crank! Talk about power, and oh by the way it happens to sound marvelous as well rivaling and besting amps many times it's price. For me it just doesn't make any sense to buy direct from China when something as good as a JWN amp is available right in our own back yard for approx the same cost. Just my 2 cents and as always YMMV

Metman: All your points are well taken. I have no doubts that it's easy to find (much) better amps than the Yayi. One of my personal favorite happens to be from a similar operation as Jim Nicholls' JWN amps: I truly enjoy Triode Lab creations ( - and their parallel business of refurbishing classic amps ( As such I know your feeling and you are right (although they cannot match the price of the Chinese products - workmanship alone prohibits that).

I guess my general position regarding China is that amps are made by people - not a country. Few doubts the prowess of an amp made in some of the old Eastern Block countries - with limited access to quality products. If an amp can be made well by Jim, it can also be made well by a caring Ukrainian or Chinese audiophile. And some do make them well, as their output of private label units for American and Euro brands proves. Finding them is hard and a gamble.

What to think of all of that? Not much, really. These are simply options with upsides and downsides. At least it's how I see it. I would not recommend the Meng Yayi push-pull to another purchaser (although I had fun along the way). Next time I'll try something else! And like you say: YMMV!


My amp was almost the same price as two of your momoblocks (very close) but monos do give you the flexibility for seperate channels for H/T purposes. Hope your happy with the amps. I give you credit for doing something that most people (in the western world) are somewhat hesitant to do. If not for people like you taking the plunge and relating your experiences a vast majority would never truly know what to expect buying direct from China
I just bought a new Jolida JD502P and it looks and sounds great (inside and outside). It's Chinese/American.

You may recall from my review that one of the two amps (that I'm using at work) suffered from an irrelevant burned blue led from under a tube. Who cares, right? Well the same amp suffered from a partial meltdown last weekend.

It went like this:
I forgot to turn off the monoblocks when leaving for the weekend. A day and a half later the fire alarm was triggered and I got called in right away. The amp overheated and was gasing out smoke (like burned insulation - quite nasty). I turned off both amps right away and all was otherwise okay.

Back to work the next day I turned it back on to see what would happen. Sure enough it started to smell fairly quickly and it wouldn't play. No surprise there.

Then I tried something.
Remember that these are integrated monoblocks. I decried that in my review. Doesn't make full sense to me. Yet it proved useful as I was using the integrated preamp circuit in my shop. The thing is that the computer does not provide enough gain to drive the volume very high. The gain from the integrated preamp circuit solved this and gave plenty of power.

So what I did is I re-plugged the cables back (bypassing the integrated circuit) into the straight amplifier inputs. To my surprise the amp suddenly worked just fine, and the smell went away. My conclusion is that the preamp stage burned out, but the rest is fine.

So I'm good for now. But this last problem nailed the coffin. I will keep using the units until they die (just because they're practical) but my next move will be a bit more, shall I say, thought out.

In the meanwhile I hope that my experience will prove entertaining (it is to me!) and useful to other people.

thanks for the update.

I recently bought a Yaqin MC-10T tube integrated amplifier that uses EL34s and a brace of 12AT7s. Honestly, for the price, I couldn't be any happier. It certainly sound better than quite a few vintage amps I've owned. I've even replaced the stock tubes with some RCA 12AT7s and some (real) Mullard EL34s. I also replaced the cheap blue coupling caps with some Wimas I had in my 'box of stuff'.

Output iron (underneath the round green cans) are massive - almost the size of my old Dynaco Mark III amps. The sound isn't "tubey" in the normal sense - but is very fast and detailed. Treble air bests my Threshold S/500 and the tubed midrange has more of that "enveloping" 3D sound. Of course in the bass department, the SS amp bests the tube unit - no surprise there. So in the end, I bi-amped my Magnepans, letting the Yaqin run the tweeter panel, and Threshold do the bass. It's a beautiful marriage.
Dividebytube: Sounds like you got yourself a nice system and it works well for you - awesome! :-)
Isn't it where all the fun is? Tweaking is a beautiful thing, and quite addictive I might add. Glad to hear it pans out so well for you. Your Yaquin is a step up from the Meng Yayi - maybe I should have gone that safer route! ha ha ha!

I was about to try some tube rolling (like you I got some Mullard plus a nice set of TJ Full Music); but suddenly the latest mishap happened, pretty much destroying the Integrated preamp stage. Oops. Since the tubes I got were all for the preamp stage, well, that went nowhere fast. Next time, I guess. There's always a next time!

Have fun and keep enjoying!


In my last update I mentioned how one the monoblocks started to smoke leading the preamp stage to gave up. Well, the whole amp it is now officially dead: in a second spurt of smoke that left interesting streaks along the vents of the chassis, it ceased functioning altogether. May it rests in peace.

(Actually I am keeping it for spare parts and for fun, but it is quite dead indeed).

Since I do have a spare unit at home (remember, I originally got 5 of them) I brought a new one to my office to replace the dead one. So all is good. Well, kind of, right? Ha ha ha - the whole thing is quite fun actually! It sure makes for great stories!


I hope to share with you all my experience in buying my first tube amplifier, Meng Yayi KT88!.

Initially, I starting reading in internet about tubes, how the amp is designed, which one is better ( class A ot push-pull).I decide on below specs.( please pardon me if I am technically not right I am new to tubes!)

1. My budget was around $700, preferred monoblocks than integrated stereo amp because monoblock would provide good channel separation and good total stereo effect.
2. I wanted the amp to be totally tubey, no Solid State even for the rectifier section.I believe SS will add it's own sonic signature to output.
3. The amp should have good weight( I assume it will have good transformers if it is heavy)
4. It should have old design (so as to see the beautiful lights coming from the tubes while listening to songs :) ).
5. the power amp section should use KT88 or El34 tubes as they are widely used. Preferred EL34 as many internet reviews said it sounds more tubey while KT88 tubes are more bright and bassy.but KT88 has more power.
6. The amp power should be more then 40W so that it has enough power to drive my JM lab Focal 725 series towers and I can use the amp parts to mod it myself to get a better amp in case the amp sounded bad.

Finally, I short listed two sites to 'choose' the amp from, and becuase they have wide variety of tube amps and cheap ones too.

There was only one monoblock which almost matched my requirement, YAYI KT88!, it had tube rectifier, a big choke and KT88 tubes and within my budget too!.
I ordered YAYI KT88 from ebay not from above sites as this ebay seller was using UPS courier service. if you're in Bangalore, India then UPS is best, the product came home in just 5 days!.HongKong post takes 15 days or more.
so they arrived, the packing and other things were EXACTLY as mentioned by Serge!.I found all ok except,
1. There is no manual!
2. The input selector in one of the amp was loose!. I inspected it and found the switch nut was not tightened, I rectified and it myself.
3. There was major structural difference in one of KT88 power tubes, the entire metal structure inside the tube was leaning on one side! but is working fine!.
4. I checked the circuitry inside and compared with the schematics I got from the seller, nothing matched!. The resistor values were different and what more the schematics had 3 transistors but none were there, the schematic had transistor based current source connected to Long-Tail pair (LTP) differential amp using tube 6N8P, instead they just had one resistor in it's place. but anyway only in ideal cases you should have current source otherwise a resistor is ok in LTP.

Finally, I connected the amps to Jm Labs Focal 725 towers and started the music. There is very little hum which is subsiding day by day. definitely there was something better in the sound than SS amp ( compared to my SS amp Marantz and Onkyo Sr805). But I could spot some distortion and things were lost ,particularly when playing rock music and in songs where music is complex. Classical and instrumental were mind blowing.Also I felt the amp had edge towards being clinical. The bass is tight and highs are bit more but not too clinical as SS amp would sound.Mids were low , typical character of KT88.But totally I couldn't accept the sound. I knew the tubes can sound better.

Meng YAYI KT88 uses ultra linear mode, there is no option for triode mode. triode mode is more sonic and smoother than UL mode but you lose output power by almost 50%. I deicde to mod the amp and using one 220 ohms resistor I changed the amp to triode mode.
Now, the amp sounded fantastic. there was no distortion and sound was simply smooth and mids were too good. Highs were pleasing now.Bass has reduced a bit but still tight and punchy, now I can recommend the amp!. The reduction in power is not a concern as still I am not using more than 50% volume!.Now I am listening only to the tubes!.
I would suggest that you buy this amp only if you know bit about tubes or else take it straight to a service person and get it inspected first.Change the amp to triode mode if you like the sound to be more tubey.

I hope this review will help out those who are looking forward to experience tubes but cannot afford to buy expensive ones.

Santosh Bhandiwad
Hi Santosh,

Great to read your review and your own experience. It seems that we agree on something here: the chinese workmanship on these amps have a lot to be desired!

Thanks for the suggestion of changing the amps into full triode mode. I didn't know that it could be done. I am tempted to bring them to my local service people to do it. Is it complicated? I wouldn't want it to cost too much (otherwise it kind of defeats the purpose of affordable amps!).


Gee,I hope folks will get to the part of the story where the thing ends up in flames, and not just stop at reading your review where all is A-OK. Such a long glowing article on how great the stuff from China is - NOT ! You learned the hard way to say the least ! May your review inspire others in the right direction.
Thanks for a very nice post and refreshingly honest review. A little "oh well!" attitude was also refreshing to read. Thank you very much, wish more posts were this unpretentious. Good luck with the rest of your amps... until there are no more left... :)

Hi Tholt & Sonicbeauty,

You know, when things go bad, I always find it easier to take it with a grain of salt. It's not as if I didn't know any better! ha ha ha!

I had five monoblocks to start with; 1 totally died (after opening it I discovered that a good chunk of the circuit board melted along with the blown capacitor - bye bye forever!); another one has a non-functioning pre-amp stage; and one was already repaired by a technician.

On the bright side two of them have played over 40 hours a week for close to 2 years now. I'm guessing that the tubes must be in pretty bad shape and that the bias value must be all over the place. And yet they still play, and not half bad either. Then again, let's be honest, it's just in my office and it's too noisy to be picky anyway.

BTW guys, do you know any other amps I should stay away from? I'm thinking maybe a big bad boy like a 211 or 845 could be fun to toy with. Just to see how long they'd last... It's kinda fun, actually....!


Update - life with YaYi KT88 mono blocks and Dynaco ST-70!

After a month of burning, one of the KT88 glows red hot, it said I had enough.
replaced and fixed the tube with Electro Harmonix brand and all is well now.
Issue was with bias trimmer, it was getting too hot.I opened entire circuit and started inspecting found below issues,

1. all bias trim pots are not of sufficient watt, connect 33k resistor in series with each pot to reduce the voltage across trim pots.
2. one of the mono block had missing filter capacitor! which is used for smoothening B+ for driver stage.

It was time for me to get one more tube amp and compare the performance. so I ordered famous (and cheap) Dynakit st-70 from ebay, it was in mint condition, only thing missing was 7199 driver tube which is expensive.
Now my mind was all in to Dynaco, I modified driver stage to use replacement inexpensive tube 6GH8, which is same as 7199 but has different pin layout. I started the engines, and found
1. Sound is dynamic and has good stereo image
2. Sound is bit harsh, typical of any amp with Ultra Linear connection in output section. The mids were influenced by bass.
3. the high frequencies were not smooth but surely this amp has very good output transformers.

I decided to improve the performance of dynaco by,

1. Eliminate Pentode driver tube, triode tubes always sounded good to me. Change driver tube to use 12AT7 tubes you need to cut some copper lines in pcb and rewire, only 4 wires required to modify no other components required changes.
2. triode connection - remove UL taps and connect 100 ohm resistor across 3rd and 4th pin of El34 tubes
3. Double all power supply and bias filter capacitors values.

Now the sound was superb, smooth highs and punchy bass, this was best sound I have heard in any tube and SS amps.
Now back to YaYi Mono block, after listening to Dynaco the sound from mono block sounded awful .I modified the entire driver stage as below, taking learning from Dynaco ST-70
the goal was to.

1. Reduce the capacitors involved in the circuit as they introduce phase shift and alter frequecy response.
2. remove LTP phase splitter as it's performance entire depends on grid decoupling cap used. Also it is hard to balance the output both mono block had difference and had imbalanced output. Challenge here is how to get the wide voltage swing provided by LTP to drive demanding KT88 tubes
3. Remove pentodes from driver stage.I find they are actually used in RF circuits why use in Audio and they have bit harsh sound.
4. reconfigure the amp to use triode mode.

so I did below modifications,

1. Replaced the pentode input driver tube 6J4P with 12AT7, used same octal socket by utilizing tube adapter, purchased from ebay.used the tube in cascode operation with 3.9k resistor.This configuration has low noise and high gain, which is required to drive split load phase splitter. This surely gave me good stereo phonic sound with smooth highs .
2. removed dc blocking input cap altogether as most preamp have it in their output section anyway.
3. The amp uses LTP as phase splitter, the performance of LTP entirely depends on the decoupling cap used. replaced it with split load splitter using 56K resistors.This configuration is simple and has good balanced output.

Now entire mono block had only two capacitors, even 2 KHz square wave out put from the amp had sharp edges and no curved bends. the earlier out put has bit of oscillations and spikes ( although you can reduce them using low value cap in across feedback resistor but you will have rounded edges)

Now the Yayi sounded much better, the high were smooth and mids were almost comparable to EL34 output. It had better tighter bass than Dynaco.It is almost a month I have been using Yayi pairs with no issues. Hope they live longer!