LJM L12-2 Amplifier Kit (Aliexpress)

[@MichaelBeeny]

This is one of my favorite amplifiers. With 40 volts and 8 ohm speakers the supplied heatsinks are OK (just) but with a full 50 volts. However, they are well under rated for 8 ohms and will almost melt into 4 ohms. A couple of worthwhile mods I have done. Fit a preset pot to adjust the QI which does vary quite abit from sample to sample. The other is to match the first 2 transistors. This will give you the lowest DC offset, typically 10mV or less. Most ABBA recordings are quite poor in quality, however THE DAY BEFORE YOU CAME (I think that's the title) is a really good recoding, lots a really low clean low-end. A good test for any amplifier/speaker combo.

[@Elecifun]

Thanks for the mod tips Michael I will check them out. I'm not a big ABBA fan although I do have a greatest hits album, admittedly I listen and enjoy. I'm on a Roberta Flack binge ATM. Her First Take album is fantastic. If your familiar, the track 'No way to say goodbye', beautiful. Checked my ABBA album and it does not have your recommended track. I will go looking for it as I am intrigued.

[@Elecifun]

@MichaelBeeny I found the Abba Visitors album with your recommended track and have now purchased. Cheers for another tip.

[@MichaelBeeny]

A great dem track, was I right??@@Elecifun

[@Elecifun]

@@MichaelBeeny I will feedback once I receive the album.

[@Elecifun]

@@MichaelBeeny I listened to the Abba Visitors album and 'The Day Before You Came' track. It does sound nicer than some of the other tracks I've listened to. As a demo track I would suggest from the same-ish era, Lou Reed 'Walk On The Wild Side'. Nice bass, vocals and the sax is excellent. I suppose there is a lot to be said for production quality. On a different note... Whats happened to your channel? Can comment, ask questions?

[@max79444]

I built a L12/2 mk 3 in October 2023 using a case from a Samson 500 DJ amp. I added a second heatsink because the original one was slightly too small to accomodate both L12. It's fed by a SMSLM500 DAC into KEF concertos circa 1970. Amazing sound quality

[@Elecifun]

Thanks for your comment. Your DAC uses same chip as the Soundblaster AE-9 in my PC. Very nice. I use a Hiby R3 Pro with dual ES9218 DAC's as stand alone music player, battery powered..clean. I to use L12/2 as my main amp and its only rival so far is Symasym 5-3, that although didn't do as well on square wave at sub 30Hz does sound very nice. Monitor Audio, Monitor 300 speakers are my choice for full stage and down to 35Hz on a budget. All together I am very happy with the output, given my music is only CD quality.

[@Sonic_Ox]

I like the idea of a two transformer set up with each channel having its own power supply. Heavy but better. I also really like your tidy capacitor banks. If you decide to build the system into an enclosure I would be keen to see what you come up with. Great series Elecifun. Thanks for posting these vids. Cheers amigo 🍻

[@Elecifun]

Well I would like to build into an enclosure or enclosures as mono blocks. Two separate transformers ensures your channels are not competing for juice when under load. I wish the enclosures were not so expensive.

[@Sonic_Ox]

I know you're really handy and capable. You can probably build a suitable, elegant, interesting enclosure cheaper than buying one.🤔

[@Elecifun]

@@Sonic_Ox I wish I could. I don't have the tools for wood or metal working. I would like to use a metal enclosure and then check the noise on the amp again.

[@Sonic_Ox]

I understand. I'm fixed ok with metal working tools but my woodworking tools (and skills) are woeful. I like building enclosures with the 3d printer but heat becomes a consideration with plastic. All part of the fun I suppose. I've been experimenting with printing drone parts in TPU with mediocre results. It's a difficult material to print. I ordered some parts to convert my printer to direct drive extrusion. We'll see if it helps. I think the stepper motor on the new unit operates on 24 volts where the old one is 12v...🤔 I may be seeking your advice on switching voltage in the near future. I know just enough about electricity to injure myself lol.

[@Elecifun]

@@Sonic_Ox I do want to learn some wood work as I want to build my cats a swing bridge and running and sleeping shelves. I need to get some sleep and the youngest is always jumping all over me through the nights. For quad frames plastics won't cut it. Light, strong and as ridged as possible. Carbon is the way.

[@Sonic_Ox]

That is a very clean looking build. The data would indicate that might indeed be "the one" lol. Thanks for another interesting and informative video Elecifun!

[@Elecifun]

Your welcome Ox. Please remind me what tube pre amp you bought. Does it use 12V AC power supply?

[@Sonic_Ox]

I forget the brand. It's one of those chinesium units from BangAliGood... yes it requires 12v AC input. I had to find one on the interwebs because none of my wall warts delivered ac at 12v.

[@Elecifun]

@@Sonic_Ox The fella that created the Audio Analyser software I use modded his and the difference is really good. Check out his vid if you want. Mod parts are jelly bean cheap. kzbin.info/www/bejne/roexfqNtqd9pmNEsi=kqCtvunTwhRN4m03

[@Sonic_Ox]

​Thank you. I'll check it out.

[@ivanlukic2360]

Greetings from Serbia. This amp is slightly simplified Doug Self's Load Invariant Amplifier from his Power Amps book. LJM kits are among the best value for money Chinese kits on the market. I've built several and always had good results.

[@Elecifun]

@ivanlukic2360 Greetings... I agree with you. and it does sound nice.

[@johnwalton5576]

I just discovered your channel in my home feed, and I really like what you are doing. So hello from a new subscriber, and I am looking forward to enjoying your content.

[@Elecifun]

Awesome! Thank you!

[@zoelong6021]

Like your work - because "sound" is so subjective - i always rely on the data to make sure that the amp meets a baseline standard - from there one can always EQ to your own ears If you looking for a next project - try the Lusya Symasym5-3 . I tested it at thd 0.0035% to 0.008% at 95W using a regulated 45V power supply

[@Elecifun]

@zoelong6021 Thanks for the feedback. Also, cheers for the heads up on the amplifier circuit. A great suggestion for a Christmas build.

[@Elecifun]

Can you link me to your test?

[@zoelong6021]

kzbin.info/www/bejne/iIW2i2qPfK6nj7c@@Elecifun

[@bertitolino]

You took out the ceramic capacitors, with which capacitors did you replace them? Im looking for a component list of the LJM L12-2.

[@Elecifun]

@bertitolino hi there, no changes the kit is what Aliexpress store sent me.

[@decem_unosquattro9538]

It would be interesting to buy the new BJTs and redo your tests. Would it make any difference?

[@Elecifun]

Not sure if its worth the effort. Are you familiar with the saying, 'If it ain't broke don't fix it' lols

[@decem_unosquattro9538]

@@Elecifun Yes I am and yeah that's wise. 😂

[@decem_unosquattro9538]

@@Elecifun The reason I mentioned this is because I read on a forum that these BJTs we're using are fakes. That's what he claims. It would be interesting to buy new Sanken BJTs and see whether it makes any difference to the "harmonics" ! I think that's why you called them. 🤔

[@Elecifun]

@decem_unosquattro9538 Fakes, copies, re-licensed who knows. It could be argued that some copies do not have all the propriety features, example, Some chip amps that are copied work just as well but are missing a feature like thermal protection. I would imagine some fakes/copies are re-licensed. Buying genuine is far more costly and the better practice overall, saying that I have replaced fakes with genuine and not really found a difference. I guess if the fake does not work then replacing with genuine a good idea?

[@ririeiman]

how do weknow which secondary transformer who will conect to become virtual ground? thx before

[@Mstaedt88]

Wow, thanks for the very interesting video! I am also very happy with my L12-2 Vers.4 amplifiers along with the B&W CM4 speakers. The Sound isn`t as worm and strong as with my old Audiolab 8000s, but very close. Another question: Do you have any experience with the amp kit`sfrom Aliexpress with an integrated circuit in it - OP07 ? Specialy the Burmeester clones 933 kits? best regards from germany

[@decem_unosquattro9538]

I'd like to see you mount it into a case/enclosure with transformers and of course the amps/radiators. 🤔

[@decem_unosquattro9538]

Wow ! 😂 I really like these bigger amps sir and that laugh.@23:57 "... that's pretty damn good! " evil laugh ! Ha ha Interesting video although I don't understand many of the stuff you talked about. Interesting that you can hear something else within the music when playing ABBA "the woosh"! Also it was interesting to note that ceramic caps are not ideal on an audio amplifier. What speakers are you using? I know you blew one out but never heard what happened? Did you buy another one? I'm thinking of buying some 13" or bigger speakers for my long term project. Right now it's just a dream still I'm hoping I can afford it eventually. I'd like to build a three way bass reflex cabinet with three speakers with a crossover so that each frequency range is segregated. I hope I said that right 🔊 🔊 🔊 It won't be easy to afford because the speakers aren't cheap. The cabinets dare I say I can build myself albeit it will be testing my woodworking capabilities. I want it to be pretty grunty. My mate built a really nice system at 17. I think he used 13" bass drivers or maybe 14". I can't remember. Still I know the sound was unbelievably good. 😂 Anyway thanks for uploading this project most interesting. So what's next? 300-400W amp next? I can't wait till your running 12 transistor amps. 😮😅

[@Elecifun]

This amp has 19 transistors per channel, which should satisfy your 12 transistor fetish, lol. My listening (not bench) speakers are Monitor Audio, Monitor 300's. I have the cheapest version and yet they sound great, its not all about looks. Lows 34Hz and 30kHz highs. 2 x 6.5inch bass drivers a 6.5 inch midrange and a precise soft dome tweeter per speaker. I'm not sure about 300-400W amps as I have no use for them. A nice 30 x 30W amp with some decent sensitive speakers will provide more than enough for most listeners. These amp kits and my speakers sound good here, clear detailed, full frequency range and enough power to rock out the neighbours a block away. Bigger isn't always better 🤣

[@decem_unosquattro9538]

@@Elecifun 19 transistors. Are you sure? What I mean is those 4 transistor thingys. 🤔😄 I'd need 300-400 to drive 13" speakers. I've already looked at the specs. Well I know trannies do two things and one of them is amplify sound. Okay, I wondered whether you fixed one of them. Didn't you blow one? I'm sure they're a nice set of speakers. I bought some ARs(Acoustic Research) years ago and yeah I love their quality still those big speakers bass drivers were just awesome. Thats what I want to build for sure. When, how? I dont know money is an issue also there is much I dont know about amps. Your knowledge is beyond my level of comprehension. Well it may be true that size doesn't matter but speakers hmmm. 🤔😄

[@decem_unosquattro9538]

Oh have you got a turntable? Do you or have you heard much vinyl recordings?

[@Elecifun]

I have some vinyl, most was lost to an angry X decades ago. The turntables I like I cant afford, i,e AR, Rega Planner, Crystal etc.

[@decem_unosquattro9538]

@@Elecifun Just get a mid ranger. Maybe $1000 anything beyond that I think maybe its a waste. Damn that's so depressing to hear that you lost your vinyl record collection. Sigh. Sadly I lost most of my vinyl simply because I was homeless. I couldn't carry them simply because I had no wear to store them. My bro in low ended up with all my vinyl. My sister divorced him and now we've grown apart not that we were very close to begin with. I bought Fleetwood Mac Rumours 3x. All got stolen. I had quite a good collection which kinda hurts how I lost them all. Another dude I new a 15 years stole my another vinyl record I had. One day I'll buy another phono. I was kinda hoping you might get some bigger speakers like 13" so that I could gloat over them. 😂👍 Anyway its obviously not your interest and your happy with your current setup. Anyway thanks for the video its most interesting. I might buy this amp at some time. I painted another wall in my workshop. Also my newly plasterboard sheet has got its first coat of paint. I'm bogging another wall which should be ready to paint. Once thats done I'll start replacing weatherboard and insulating walls. I'll start with the worst rotted out walls. Then later I'll tackle the other walls. Anyway I look forward to your next video. Are you going to assemble all your amp parts into a case. I'd be very interested if you are. Anyway its late here. Goodnight. 😴

[@decem_unosquattro9538]

Where did you buy your t. transformers from dude?🤔

[@decem_unosquattro9538]

You bought the kit right which is stereo? Are you buying an enclosure for it? Another toroidal transformer? 300VA 2x30V?

[@Elecifun]

@decem_unosquattro9538 I don't know. Enclosures are expensive, I have limited funds. I like building the circuits and feeding back the data. I will probably buy another transformer ready for enclosures. This will take some capacitor loading stress off the single transformer.

[@decem_unosquattro9538]

@@Elecifun you're right they're like $150AU for a cabinet. Hmmm

[@decem_unosquattro9538]

@@Elecifun Transformer ain't cheap either. 🤔 I don't know which way to jump with transformers. The AliExpress transformers are very disappointing.

[@decem_unosquattro9538]

@@Elecifun If you do decide to buy a cabinet at the very least you don't need to buy radiators. I notice they are essentially radiators. I guess the go is to buy another transformer and then choose the smallest case/ enclosure possible? Buying the biggest probably not such a good idea 🤔

[@decem_unosquattro9538]

@@Elecifun Anyway this is going to buy an interesting build for me. It might be a better idea to buy a smaller set of speakers. I'll build the speaker boxes myself. The only problem is the dimensions. 🤔

[@decem_unosquattro9538]

Hey Sir back again for the 3rd time. Can I ask you what size transformer you used on this amp? It's says 55V and I saw a dual 55V transformer 120VA. I wonder whether I should get one or two like I think you said in your video.? 🤔 I'll take your advice and get the film cap, and the two electrolytic caps instead of the two ceramic capacitors. I can't wait to get the LJM L12-2. It shall be mighty interesting project. Oh incidentally I saw a pair of speakers which is even bigger than what I'm planning on building. They really are awesome 😅 Imagine those beside your telly. 📺 Two 13' sub woofers. You'd need a beast of an amp to drive them.😁 The speaker enclosure looks like a real nightmare to build.😂 Edit okay you're using a dual 30V transformer. Hmmm.

[@Elecifun]

The dual 30v AC once rectified provides around 42V DC mine is 300VA. Not sure what you refer to when I said film capacitors.

[@decem_unosquattro9538]

@@Elecifun I noticed you replaced three caps with two electrolytic and a polypropylene cap.

[@decem_unosquattro9538]

@@Elecifun That's was good timing. I just got home.

[@decem_unosquattro9538]

@@Elecifun so what ate you going to do sir? Buy another transformer?

[@Elecifun]

@@decem_unosquattro9538 If I were to case the amp then ideally I would buy another for mono blocks. At the moment one transformer is fine, I don't push the amp so I'm not worried about voltage sag.

[@amdbtk]

Hello. Very nice video. Thank You. Where is the blue wire connected to on the attenuator? MVH Tamas

[@Elecifun]

Glad you enjoyed the video. The blue wire enters the attenuator / voltage divider from the amplifier ground output. It leaves from between the two 10k resisters and enters the AD2 via the scope 1 negative input. Dividing the output voltage by 2.

[@amdbtk]

Huh. So You attenuate both the + and - of the amplifier output and the green goes to the AD ground?

[@Elecifun]

@@amdbtk Yes, remember the AD has differential inputs + - . The green goes to ground.

[@remusboldis6177]

This kit is also supplied in class A, have you tried in class A?

[@Elecifun]

You can switch it to class A by turning up the quiescent current. I haven't tried.

[@decem_unosquattro9538]

I've change my mind; I'll get the 300VA but I'll change it to 2x35V on the secondaries.🤔

[@Elecifun]

Sometimes for the very small extra gain on output its not worth pushing in maximum voltage. 30-0-30 is a good trade off.

[@decem_unosquattro9538]

@@Elecifun oh okay. We shall see when I go to buy the transformer/s.

[@decem_unosquattro9538]

@@Elecifun How's your diet and health now? I'm back doing push-ups again.

[@Elecifun]

@decem_unosquattro9538 fair play to you. I am using an elliptical trainer for exercise as I get to listen to music without headphones or watch a movie while working out. Getting more fruits and whole foods in me, I don't like the idea of processed foods even if they taste good.

[@decem_unosquattro9538]

Sir, what was the THD? .001 right?

[@Elecifun]

No I don't think so.. did you watch to see?

[@decem_unosquattro9538]

@@Elecifun I think you said .001 which is obviously no where near the .0005 in the specs still I can't say I'm surprised. I'm kinda over the fkn lies that the Chinese sellers tell us. 😒

[@decem_unosquattro9538]

@@Elecifun I mean what's the point in lying? Yeah okay short term they dupe the naive customers. Sigh. I guess they're all stressed out paying their insane mortgages.

[@decem_unosquattro9538]

@5:42 Yes it does look lovely. I like it in pale blue. Very nice indeed. 😂👌 I'm having a bad day bruv. I left the date roll at the super-market. 😂💩

[@decem_unosquattro9538]

I think I might buy this kit.🤔 I can't find another amp with better fake specs.

[@Elecifun]

I think sales people tend to puff piece for a sale.

[@decem_unosquattro9538]

@@Elecifun not quite sure what you mean. I think you mean sellers make the product look better than what they actually are. Which is true if that's what you mean.

[@Elecifun]

@@decem_unosquattro9538 There are many ways to advertise products, services. Some only advertise the best points and not the bad.. That's writing a 'puff piece'.

[@decem_unosquattro9538]

@@Elecifun oh okay. Thanks for the explanation.

[@decem_unosquattro9538]

@@Elecifun Lying about specs is pretty bad. Like for example putting the THD down as .00015 and then you test it and it's .001 😏

[@decem_unosquattro9538]

Okay. @24:19 2 x 30V 5A transformer 300VA.

[@decem_unosquattro9538]

5:47 It is a nice looking board 🤔

[@decem_unosquattro9538]

Hey Sir ! Im back again with another comment.😅 I watched other videos about the LJM L25 amplifier. Well it was quite an interesting project. He used: two LJM L25 ... modules A power module (not sure what it was putting out) 70V?? No transformers I guess the power module was a switching style PSU module (something like that) It also had a speaker protection module hooked into it. He also had some DSP module powered by a power bank (i think) as an input source. (You'd understand it more than me) Unfortunately they dont appear to be available 😕 In another thread they say these modules are a bad design and they blow up easily. Is there any truth to this statement sir? 🤔

[@Elecifun]

@decem_unosquattro9538 I've looked but can't find the amplifier on Aliexpress. Maybe it was not popular.

[@decem_unosquattro9538]

@@Elecifun Maybe there was some issue with it like what was stated by some dude in some random forum. 🤔 Maybe it's like the 30V 3A psu boards. There seems to be these boards or projects with problems or design issues. The problem with stolen intellectual property is often or it seems that way. They have problems. The Chinese sellers don't really care they just want to sell something even if it's faulty. It's obviously not sold anymore. Maybe it's a blessing that it's not. It would be nice to be able to buy a diy kit amp with Maybe 400RMS and very low THD. Anyway not to worry. There must be something out there that fits this criteria.🤔

[@decem_unosquattro9538]

@@Elecifun nice and hot down here. 37°C here 40°C + father North. I'll be glad when summer is over. It's a season I hate the most. 🥵

[@Elecifun]

@@decem_unosquattro9538 its winter here. Wet and moody weather.

[@decem_unosquattro9538]

@@Elecifun I like winter and it's the only season I sleep properly. So wet and moody I like. Still I think I probably prefer Autumn and Spring. Mild weather. It won't be long before your Spring. My big debt is coming up soon. 🫤

[@decem_unosquattro9538]

5:53 A nice big chunky radiator.🤔

[@decem_unosquattro9538]

Hi Sir! Sigh, I'm currently building this DIY kit and I just noticed my board is not version 3.00. It's version 4.2. I noticed your version is version 4.00. These boards versions are all over the place like a mad women's shit ! I hate it when they do a bait and switch or when they just send you us different versions when clearly what was advertised is was version 3.00. Another annoying thing is that they don't put the parts it's supposed to have like on mine it has two odd sized thin film caps which are supposed to be 104s but they instead swapped it for 100nJ100s. I don't know whether they're fine or not! 🤬 Kinda over this bs ! I'm going to be so angry if this project doesn't work when it's finished. Fortunately I have a box of thin film caps which is why I always buy extra components. Sigh. Anyway I shall continue building it and hopefully it works otherwise you hear me ranting from England! 😂😂 See ya later dude! 😮

[@Elecifun]

The caps are fine 104 is 100nF or 0.1mF. The board sounds like an improvement. Some old stock photos still left on newer adverts. I keep my fingers crossed also.

[@decem_unosquattro9538]

@@Elecifun Yeah, it would be most interesting if you bought this version and tested it. I might buy the same Fortitude thingy that you have and test this board I have. The more people testing the less we all need to do. Incidentally I remember you saying not to install monolithic caps and instead I should install electrolytic instead but the problem with that is they are polarised. I don't know which way they should be oriented within the circuit. Also I don't think I have a 105 electrolytic capacitor. 🤔 Anyway I just soldered it in. I guess it'll be detrimental to the sound quality still this is my first amplifier. I'll use it as a sacrificial lamb. I have much to learn as this road is a long one. I started reading 📚 about audio transformers. I guess they're really friggin expensive to buy. Maybe prohibitively expensive. I'm going to buy a soft start circuit and two speaker 🔊 protection modules. My planned long term project may never get off the ground. Two weeks ago I had my gas cut off because the price is fkn insane now. No hot water. No showers No hot water for washing up which ain't good. No heating. No finances are that bad I was forced to take drastic action. Anyway my first amplifier is finished. ✅️ Now I need a transformer 300VA 2x35V Softstart module Speaker protection Unfortunately I won't be able to test run these amps until I have my head above water (financially). Soon I'll recommence my reno which I put on hold through the winter and severe lack of funds. I'll finish another part of my house when I've repainted my boards. I just need another top coat before I reclad that section.

[@decem_unosquattro9538]

I think I'm going to need another soldering station like yours. Mine I feel might not have enough grunt. I really need something with a lot more heat. They're awfully expensive to. 🫤 This project is going to hurt. Fkn sucks not having enough money. Sigh.

[@Elecifun]

@decem_unosquattro9538 You have a Hako?

[@decem_unosquattro9538]

@@Elecifun Yes I have the Hakko 951 which is a great soldering iron. I'm now thinking maybe I need to get another one for projects that require more heat.

[@decem_unosquattro9538]

@@Elecifun I'm going to need a micro pen at some stage when I start soldering the smaller SMDs like: 1206 ✅️easy 0805 ✅️easy 0603 ✅️ more difficult 0402 ⬅️ 0201 ⬅️

[@decem_unosquattro9538]

@@Elecifun I've discovered another problem with my car. The LHF CV Joint drive shaft rubber boot has split open and it's leaking grease. Another job to do. Sigh. 🫤

[@Elecifun]

@@decem_unosquattro9538 That sucks.