 Hello everybody and welcome back to my V-Log, it's my channel and we've got another amplifier circuit here on the table And a quick peek on it and Aliexpress just to start off with This is the LJM L12-2 power amplifier Ultralow distortion classic amp DIY Okay, this one says finished with radiator. I'm not sure about that I went for the two channel kit and what you get is a Couple of these and get rid of that First of all, I just want to point something out that there are different versions of this and on this Not sure if you're able to see it that clearly, but it says version three there We go down this actually might be able to Just have a peek down. I'll show that version three again in a moment. We're just going to quick look at this so what we got is Plus minus 50 volts power equals 120 watts into eight ohms 200 watts into four ohms out plus minus 50 volts. Okay The THD and Is zero point zero zero zero Five percent one kilohertz at 10 watts and This oh Yes, this is a Got a lot to put that in 35 volts us This 35 volts microsecond, this is the slew rate All right, that's like how fast it can go and it can switch between You know when things are no easier and quieter and how fast it can how fast it can move between it's a whole Topic to try and explain. I'm not going to get into that just that moment Dump in fact a lesson 200 Most of nothing and I want to know about any of this sort of stuff frequency response range 15 hertz to 50k With a minus 3db 20 kilohertz 20 kilohertz 0.02 db and that quiescent current 80 milli volt milliamps And you can run it from Plus minus 12 volts to plus minus 55 volts right voltage amplification factor is 31 times All right, so you can read upon all this anyway, but that's that little bit of information there So we're gonna just go down this now. I know I'm not a lot of these images. They're all generic You can see down here Where it's got it's very low Not quite as low as what they're saying comes in more of a not point Zero point zero zero one What we're gonna see we'll see what we get with this and This is what I wanted to show you You can hear that clothing about that's one of my cats jumping about On here as you can see see these multiple layered ceramic capacitors These are no good. No good. No good. No good. They like microphonic. So they'll pick up Vibration sounds and they'll amplify that sound through the system. They're not good this is version 3 here and Yeah, so that's no good, but I'll show you on the board that I have How that came to me now you see we're clearer here see these you don't want these You don't want these at all. That's a bipolar is here. It's more bipolar. It's in a film here but I show you in a second and The one thing about this load Is the price there Because it's class A B. So it's more efficient than the class A and The price doesn't include the radiator If you want a radiator for one of these you're gonna have to get something like this or you can find another one That's gonna be the right size and you can drill your your own holes into these are set up for different ones as well So these three here are not for this particular kit But these two on the end on each end are and the radiator The board fills the radiators quite nicely All right, so that's that there now. Let's take a peek at it itself. Here's the the kit itself On top of the radiator This is how you'd set it out probably yourself, which is It's simple enough to do as well. It may look like it's complicated It's quite nice because the the leads on these are long enough and hard enough to have this as the Amount so it's very very stiff and solid on there, which is all good And let me show you about these capacitors So if I just get that you see this one here We've got this film capacitor here and here's a little bipolar and here's a little bipolar Rather than the ceramics Because like I said, they're no good directors like small microphones and Won't do this any good whatsoever So it's it's a nice neat board. It looks lovely. I think it looks like quite pretty actually especially if you know Take a bit of time when you're doing it and Set it all out nicely. This is using all of the things just provided in the kit Which is pretty good So there's not a great deal to it there and you know once you get it and you build it up It's simple enough. Everything's marked out And I think what we ought to do now is take a peek at the actual Set up that we got so I was hiding this a little bit Just put that there funny little light today But this is how we got this Set up so I got a dummy load there connected to the output and our power now again, of course It's a positive negative power supply Usually we've got a negative voltage positive voltage in the virtual ground I'm using at the moment on this. I'm just gonna kill it like that for now. I am using a 30 volt transformer 30 volt AC so we got a 230 volt outputs We join the two middle in order to give us a virtual ground which is going in here And then we've got our one side This will be the negative side the 30 volts as you can see The negative lines on the capacitors there, and this is the positive side Which will be on the other side here Now I'm using the same capacitor bank As well I would normally use and that's all fine And the only difference here to the setup that is normal is I shift that out of the way Clearer he's I've had to build this little thing here Because the power output on this will be higher than what the input on this can take before this In fact clicks this thoughts This will because the input Okay, so in order for me to get around that just in this particular instance what I've done is I've built a little attenuator which is basically just a voltage divider and So I've divided the voltage by two So if I put a hundred volts in fifty volts comes out, yeah ten volts in five volts comes up, you know Which just means that I'm not gonna damage this and we're gonna get a clearer look at the output power on this Otherwise, I won't be able to go up As high as what we'd like to So let's give it a go then let's get it done the on the Audio analyzer and let's take a peek at what's going on. We've got the audio analyzer suite on the go Now I got to give it some Some juice I switched that down sorry if that was a bit loud We're gonna go from range from 10 Hertz to 30 kilohertz total harmonic Distortion and noise Channel one We're just gonna go for 200 millivolts RMS input and we're using eight homes as our load And we'll give that a little run. We're actually, you know, just the steps on that and we get better stepping We're gonna run that now I'd just like to say what this is starting is this is You get it see numbers here in the frequency. This is the percentage of distortion and the frequency So I've given it a bit more resolution. I've been 200 steps on this Takes quite a bit longer this ends, but you won't really get to see any difference and this is total harmonic noise and distortions so We can look over here at the percentage of distortion and we can see here the frequency We can also see down here on the spectrum analyzer. This is a nice sign. Look at this. This is minus 75 DBR All right, and we have our first There at minus 76 here, you can see the numbers here minus 93 and at the frequency So here has our two kilohertz. I believe that's going to be. Oh, sorry 595 first is our first harmonic and that's in at minus 74 point two and that's the highest as well the harmonics So that's pretty good all around and that's the second there My it's 81 Now these frequencies sorry So when we look across here, we can see this is all Pretty much below the note 0.1 until we get to about here 0.96 and we go 0.1, but this is with the noise as well So let's just filter out the noise and we look at the THD Wow That looks quite nice doesn't it? So this is 0.02 Right now you can sort of say this is in the high-five Range now. This is nice. It's a little bit squiggly there, but Still this is very nice, and this is probably the best That I've seen so far myself 0.01 there look Ten kilohertz, and you can use these peaks if you wanted to and say 0.010 Zero and even down here if you wanted to for the for the For the avatars inside of things you could call that out as a 0.006 Which is new enough going with the numbers that they've said Yeah, at that one part But that's not quibble that is that is pretty good. It's pretty good. So let's have a look at the frequency response I'm going to do the power last Just because it just lets the thing warm up a little bit I'm just going to drop these down so we get more of a zero point in the middle of the screen The same Knock the steps up Steps and we shall run that Okay, well just looking at it. I don't I'm not sure if there's anything I really need to say It speaks for itself really doesn't it? If we look at this area is our 20 Hertz 19.9 Hertz up there and here will be the DBR the DB difference against the reference voltage And in the DB of power this we look at that the 20 Hertz there. We are 0.00 DBR I said 20 Hertz Now somebody asked me the other day. Why do I bother showing on the square way 30 kilohertz? Well for one selfishly my speakers here go down to 35 Hertz So looking at 30 Hertz for me is you know pretty good and there's gonna be other people out there as well But more specifically the audio range starts at 20 Hertz and finishes at 20 kilohertz really Less if you really want to know what you can hear less than that But it you know we started 20 Hertz, so that's why I show the 30 Hertz square wave It may not be a plot applicable to everybody. You got to understand what your speakers are like Their specifics Specifications, but as we can see here, this is this is glorious. This is you know zero zero It's just staying at zero. There's no difference. So we get there zero point zero one We'll go up here zero point zero nine. There's gonna be the highest peak round about there And we're talking zero point one two DB against the reference. So Yeah You're not really gonna notice that it's not really gonna be a thing for you So let's just take a quick peek at that on the square wave, but that is lovely That is absolutely lovely, especially when you consider It's a kit It's cheap When you start adding the cost of a transformer bits and pieces it gets a bit more expensive, but it's still It's still something that's a pretty cheap. So let's just check on the scope. Let's take on the square wave Channel one of course keep over in the same and we're gonna just go straight in for the one kilohertz because that's there, you know The biggest thing let's do a single shot on the scope Boom And someone could argue oh the treble's slightly going up there. Nah, forget it. Just just ignore that That's okay There's gonna be bits noise and stuff picked up from in here This system so just you know that that's all fine. That's that does look really nice. Let's go straight down to 100 That's do a single hit there again And you could just say that that little tiny bit there is just you know So we gain on the treble remember we saw that in the frequency response anyway In the in the higher trebled areas there there we go Slight tiny bit again, and it's showing up on the scope, which is just this little tiny bit here But ignore it. There's no No point really looking at that. So let's just switch straight down to 30 as I want to know And do a single hit there When you see this coming down, it's like the bass drop off, but it's nothing It is nothing at 30 Hertz. So which means that if your speakers can represent it You're gonna get that nice Bass out of it now. I was listening to a song by Abba the other day I was decorating and I just put anything on anything that I can have a sing song to on doing the decorator And there's a bit in that song where it's it's like in the riff area of the song. I can't remember exactly But it's got this I'd never heard that before Well, I stood up here listening to it thinking it's not you know, it's not right in your face But it's there. Wow. I'd never heard that before. I didn't realize they've got that thumping You know that sort of driving bass coming in. This is Abba. Come on Anyway, that's the difference. This is can be the difference between how your amplifier and your speaker Can re-represent that music back to you So so let's just for the sake of it because we start at the bottom of the frequency on 20 Hertz and we're gonna the AF frequency and we're gonna Just the audio frequency, I should say Yeah, that's that's it. I mean there's hardly any difference between that and 30 Hertz isn't so that's all good Now, let's go up to that's five four K Yeah, five kilo Hertz Lovely I Wouldn't be able to tell you this is that slew rate thing This is the adjustment how fast can it go up now I wouldn't be able to tell you whether this is my measuring or whether that's the amp and To be honest, you know There's not enough there to really complain about Let's go to 10 10 kilo Hertz again, you know Not enough if it was like, you know all the way off or something might have a problem, but no, that's that's good Now we're gonna go to the Top end which is 20 kilo Hertz Look at that again Not a problem at all Not a problem at all. There's a little bit there, but I couldn't tell you whether this whether my my Dissident here can actually You know register it that quick Whether the waveform generator can output that quick So let's go to 30 kilo Hertz because that's what my speakers go up to and plenty of your speakers will go up to that Let's have a look at that there. Lovely Not a problem not a problem I'm impressed Just because it's a little bit more expensive, you know, you're gonna buy the radiator Yeah, but considering some of the ones that we've tested I've not really had as good outputs as this It's this isn't I've got a I've got to say it is because this does not tell you sound quality All right. This is just the Responses from it as an amplifier There's a circuit But it's not going to determine sound quality because we got to remember someone well a lot of it's pretty subjective Now we're gonna go for the one that a lot of people don't want to know now Remember, we got a 30 volt zero 30 volt which means we got 42 point two volts or something 040 point 42 point two volts something close to that 42 point three DC So it gives us about an 80 some of all swing. Yeah Just have those two together So total harmonic noise and distortion we're gonna go for With a test frequency and kilohertz bandwidth 30 kilo 30 kilohertz Test frequency one kilohertz. We're gonna stop at 1% Distortion and all right, we've got a load impedance of eight ohms And we got a range from one watt to 100 watts, so let's hit it. Yeah, I do this blast just because Circuit would have warmed up and it's you know better not just to stress it out from being cold and Trying to push it to its its limits here Okay, so there it is Now the reason why we've put this Using the differential side of this scope and we've put on the The voltage divider is because the attenuation ratio down here be a two to one That's why that's in there is to in case anybody noticed And as you can see before we hit that 1% Which will be going right up on the edge here in actual fact It shows us that we've hit 100 watts as possible that we might be able to get a little bit more than that But we have 100 watts So I just pushed that right to the edge 99.082 watts 0.068% distortion Well, it's didn't quite get up to the but what now I could probably do that again and set it up to a thousand watts here But I think I think that's doing you know, it's doing what it's supposed to do there And I don't know how warm this is here Yeah, that's pretty warm. So then We're just gonna leave that like that and we're gonna say right. Well, there we go This is our output from it now It says it can go up to minus 55 Which that means you can't use you could use a 35 volt output transformer. Yeah to lots of 35 volt AC And that will get you, you know, 50 50 volt something like that But if you go up to 40 volts trying to get you 55 it's actually go to like 56 and a half and I don't know, you know, I don't see the point in putting the maximum voltage in because that means you're running that full pressure and You're probably kinder to the to the components and everything else and the reality do I do you actually need that? At full pressure. No, that's why I've settled I settled for 30 volts 0 30 volts because it would give me that 40 42 volts output And I can also use that on other amplifiers up so they can go to like 45 volts, which is great So, yeah, there you go So I know you there's some guys out there that will be happier with that because you're gonna get your hundred watts And this is at eight homes All right, now we could set up and go for a four-aim load and see what we can do there But this time we're gonna run it on four aims and See how that goes Alright, this is one to one thousand watts Please nothing break. I'm just hoping it's cool enough. Yeah, that should be alright. Let's give it a go Okay guys, so there we can see All the way across this is quite nice again the crossover point is basically the same as the last time Well It's nearly twice the voltage Watts as last time well as we can see this is where we hit the hundred watts There's ninety nine point one. There's one hundred watts zero point zero six four percent and as we get into the realms of Let's say a hundred and fifty watts zero point zero five percent and as we do our crossover to one percent distortion We're on a Let's just put that right on the peak there hundred seventy nine point two nine watts And if we just take this from the zero point one percent on the crossover there were a hundred and seventy two point two eight four Watts at zero point one Zero nine percent distortion That's pretty darn good That's what and we're gonna remember as well. I need to bring the camera over now Sorry about my chair making some noise. I will invest. I will invest in a new one soon to try and cut that out But just what I want to add to this as well is I'm using this is 30 volts five amps zero 30 volts five amps. This says 300 VA this and I I have Well, my ideal setup would be to have two of these one for each channel To ensure that when it needs it it has that grunt It's not gonna need it all the time when it really does need that grunt It can pull it from the transformer without pulling the voltage down you pull the voltage down You're not gonna get the output and I think we can see on the screen that that does work quite well So that would be a monoblock set up the transformer the capacitor bank and The amplifier itself as a monoblock two of those left and right channels Ideally I'm sharing The capacitors and the amplifiers at the moment between the one Works very nice, but I prefer to have two of these so when I can find another one these exactly the same for a good price I'll probably buy another one. This is the one that I'm gonna have for my home hi-fi listening it's very enjoyable and And it and the output show that it does fall into the grade of what would be called high fidelity It may not be the best on the planet But look at what it is you're buying and look at how this isn't screened or anything like that But fortunately it's got a differential input Which means it gets rid of lots of noise and stuff automatically. All right Thanks for watching and I will catch you guys very shortly in the next one