 Hello everybody welcome back to my channel to my V-log. Hey now, what's going on? Why can't I? I can So here on the bench at the moment we got a one of these little LM 1875 his chip out And we go these little kits you can buy from Aliexpress. I Played around with a few of these, you know changing our capacity and stuff And there was one that I got slightly better performance on but it was no good in four arms So I was pointed out in the comments By JAT John audio tech, which he was absolutely right, you know, the man's a He's a pro when it comes to this stuff But I just play around sometimes in here, but this is just a straightforward kid Okay, so this is what you get from Aliexpress And I've got this to bring a bunch here. I've got 25 volts coming into it And from over there on the Over there on the power supply. Yep 25 volts coming in and We are connected up to an eight-ohm load I Built a little voltage probe Yeah underneath there there's another not that you can see I'm there This is a voltage clamp there, and this is basically an attenuator and it's attenuates minus 20 dB So if I'm putting in 10 volts It will actually be outputting into the auxiliary input of my measuring device It'll be outputting into that one volt and if it were 20 volts it'd be two volts and so on and then It's clamped around about three and a half volts. We can't go any higher because of the diodes so That's what we've got going on. I'm still using my Old cable and I will get around to doing that about the cables and just showing you the difference when it comes into During the calibrations and the difference in the cables But we got here so far as it said we take a peek at the screen I've already just run this and I've run it to And got some averaging on it just to clear up the the bottom of the lines here And as you can see down here, we've got our RMS. It's minus 3.5 dB FS It's car rated up to minus three So I'm pretty much as close as I can get and if I do go any lower than that this particular chip animating 75 well, it won't be happy and Get about about five and a half percent distortion But just not quite peak we've got 0.042 percent Distortion nice nice low noise floor, which I couldn't calculate before and I'm gonna tell the difference now is if you imagine that When I was doing them before my noise floor there was a hundred and five minus 105 dB So if you look at this, this is like 100 and 120 halfway They'll be 100 and 10 and then we go a quarter way up 105 So my noise floor was here and this is the noise floor here, right? But my noise floor was around here, so I could only measure from the noise floor upwards Anything underneath here was gone. It was noise because of the device I was using So that's why this is a better Way of measuring because we get to see this without the noise so much which means that when we're doing the measurements we get to see the THD and The noise isn't in there as much as you know as you can see there were pretty much equal on both of them Right, so yeah, so that's that that's I mean that that's pretty good Do you know there is a way you can measure all this you can work it out You can do all the RMS values of the all these peaks square them I'm just very square RMS value squared and blah blah blah all the way down and Take all that and it all together square it again and they're getting close to working out mathematically or the THD is but You read up on that and you just think so now that's just too much one of these That's what my brain tells me it's too much too much of the scope of things of what I'm trying to do anyway And there's and there's great bits of kids software that do it for you, so Let's take a peek Keeping all the same values. I'm keeping the same volume level and everything Which is going to be at this minus 3.5. They'd be the first and we'll look at the frequency response Just hit that And here we go. So I just shunt this oops wrong way Shunt this down a bit we get to see here The frequency response curve and so all the way up to 20k we're good Short that is why it's not such a nice line, but 1k we're coming in I can see here that We're minus 0.7 1db down you just see I mean all we want to do is just see that how it starts dropping off on the Curve we can see from the straight line from a hundred Hertz. We're dropping down. Where are we at 70? It's not too far if we look at this being Sort of point seven. Yeah, there's point six and there's point eight So we can look at this as being sort of point seven in the middle Maybe a little bit higher than point seven. I know we get down to 50 Hertz We're at point eights. We've dropped off point one And then we're down here to point nine, let's say so we dropped off point two there You know, I'm encouraging we can go through the whole thing about the speakers again Who's got the speakers to represent 20 Hertz? This is just for two speakers. I think about when I'm doing this sort of stuff left and right channels stereo sound So that's the LM 1875 Kick doesn't seem too bad at all. We can look at that again Over there as we're doing that we can even turn this up quite a bit Turn that up quite a bit. It should take some Time doing that. I'll turn the averaging off We'll go full-pulled on it Okay, and then I'll put the averaging on and if I try to adjust the volume So we go to 3.4 3.3. You see how the other total armament distortion noise Comes in so if I back that off to See that's a three point 3.2 dbfs we got 1.8 Back that down just a little bit just so it's not on full blast Take that off. The actual fact is lower now and that could be because we've Got the averaging on and it's not being quick enough to measure it up So let's just take that back up again To six point five. I think that's what we were before but it's not that 5.5 5 Three point five that's three All right, so that is basically giving it full wallop point six nine percent We just back off slightly not for wallop zero point zero five Yeah, it's still pretty good. It's still pretty good for such a little tiny amplifier and we're sticking to the get that we're putting in 821 824 Milliamps It's working It's working quite hard Let me just get rid of Some of that noise on there. I just stop that off Take the pressure off it and yeah, our first harmonic is Not across there we go. That's the closest we're gonna get if you look at the numbers go that goes up It's not as close to the Two kilohertz and that goes up. So I always choose, you know as close as I can get so that's minus seventy two point five That's still you know, that's pretty good. I mean that is good Especially for such a little tiny you can see why some people really may run about these chip amps because I mean that is good Isn't it we have three kilohertz the uneven harmonic there is minus eighty seven point two three DB That's very very good Very very good Yes, all in all I suppose you could say that that's just for that for the total harmonic distortion It's within spec of what they advertise It's on spec of what they advertise pretty much. All right, you know you drop down that extra minus one DB against the And the fundamental signal going in there and you will find yourself climbing into distortion It's not the power supply because it's got plenty there. It's only using 850 million amps and it could go at three point two amps each side, but it's not He's down to the the chip setup, but still very good at 25 volts brilliant. Well, that's it. I just wanted to show that again because Before it didn't seem to fare so well but again, you know that was because we were limited on the resolution and From what we could actually see from that we're going much better noise floor now much lower and we get a sear much better Thanks for watching guys, and I'll catch you in the next one