 Hello everybody and welcome back to my V-Log, my channel. Now this circuit is a pre-amplifier circuit. I bought it from AliExpress. I'll show you that in a minute, we'll go over it quickly. And I just want to say it was really easy to build. Everything's laid out nicely, all the components feel nice. There is one little thing and it says that it comes with Alps. Potentiometers. And this one's an Alp Potentiometer. And it's more expensive than these ones. But these ones are Song. Now it came with three songs and I thought well I'm going to put in an Alps and just see if there's much difference on there. We'll be able to have a look. There is a slight thing there. But apart from that, all the components are as they are. They've got Nichicon capacitors, it's ELA capacitors. All the parts seem to be pretty good. I'm not sure now if I should be swapping out these carbon type resistors with metallized resistors. Because the carbons are generally 10%. And the metallized ones are 1%. But just for now we're going to leave it like this. I mean I'm not going to change this one at all. But it was pretty easy to put together. And everything's on there as you'd want. Now I've put a wire across here. And it's come down to this ground point here. Because it tells you to do that in the right up to it. If you're not going to put it in the case. And just for now it's not going in the case so that's fine. There are only two mounting points. There's no mounting points on the corners as you can see. There's only two mounting points and that's one's here. That's in the ground plane for the ground. And that is connected to ground. I did a test between there and these. And then there's another mounting point here. This doesn't actually connect to anything at the top or underneath. It's isolated. So there are its mounting points I presume. This one you put in to connect it to your metal frame. And that would be grounded. And you'd have ground because I do believe I should check it. But I do believe that this ground is going to be the same as this ground. Anyways, so what I've done is I've connected it up to this. So we've got our waveform generator here. The output here. And all I've done is I've just tied two of these together. So we've got two outputs from the same waveform generator output channel. So we know that they're going to be exactly the same. And I've got my two probes on the outputs. At the minute I've got a 33K on here. Now the reason why I've gone for 33K is because the input impedance on the amplifier I've built. They are 22K. And let's say their new NAD 3020. Because this is what this is supposed to be a replica of is the NAD 3020 pre-amplifier from back in the 70s. But the new NAD, the D3020, that's got a 56K input. So I just thought well I'll just do something in the middle. I could mess around with 1K, 10K, 22K and go through like that. But who's got the time? And maybe in the future I'll do it here. But I'm not going to do it all on camera. I don't know if there's any differences of this. Notable or anything like that. You can see that you've got two channels here. Two identical channels. And if you notice that you've got your filter caps coming in. And you've got these two voltage regulators. And then you've got one, basically one channel. Two caps here, one cap, two caps. These transistors which are actually doing the push-pull. The side of this. And then you've got exactly the same one going through here. Which is pretty good. And all the rest of this sort of stuff is for the tone control. But yeah, so it's a nice, neat little board. It's very well laid out. For what I can tell. And it's just a neat board. I'm messing around with the lighting because I don't... It doesn't matter, I've got my own shadowing I think. Not sure, never mind, doesn't really matter. Here is the actual advert. I'm AliExpress. This is the one that I bought. There are quite a few different ones on there. And the prices do vary. But I like to think I look around for a bargain. And here it is. It's all nice. Now this is the bit where it says here, with Alps Potentiometer. And it doesn't, it has these song runs. What the differences are from what I can tell is price. And maybe a bit of quality. Now here's the image where these shows on here. The cable going across between these potentiometers. And here's cable comes around and goes down into that. There is actually a hole there on purpose. So I presume that's just where you ground it to. And that's what I've done. I've just copied that. Just to make life easy for myself. As you can see it does come as a kit. But it's a lovely board. The board feels nice. Everything feels nice on it. It's a lovely little board. So we've got some bits in here that you're going to consider. And that is one of the things is the voltage here. AC, 24V, 0V, 24V. Now I don't have that, but it does say here be careful brother you must watch what the power supply voltage shall not be lower than AC dual 22V. All right. And that's what I'm using. I'm using a 22V. I don't have a 24, 0, 24V. If you are only listening to the bare board you must connect all the potentiometer enclosures with wires. That's what I just showed you. And then connect them to ground at the power terminal on the board. Now it's not gone through to the power terminal it's gone through to that grounding point like I said. Which happens just to be here. There's a hole there. And that's ground straight off this cap. As you can see it's got the stripe there. That's the ground side. So that's what I've done mine to. And in the image here as well he's done the same thing to that. I hope you can see that. But if you look it up you can see a bit better for yourselves. And the audio signal wires must be shielded by a if it's installed into a chassis please refer to one point grounding. All right. So basically I've not used shielded on the input. I'm just using this. And these are not shielded. No. They're the cheapest ones I could possibly find. They're not shielded. So if there is little bits in there we've got to expect maybe a little bit of but I can't see anything. And we're going to look at that in a minute. I can't see anything. I just got some close ups of the board and a bit of some pieces. Okay. So guys. So what we got here then is we've got it connected up. Now what I've done is I've decided to go and use 22K resistors for my dummy load for this preamplifier. Why have I chosen 22K? Well because this is one of the amplifiers that I've built and we can see as we look across here that down there going from the input to ground the first resistors 22K. So that's going to be our input impedance. And this here will be our load impedance is 1K. So that's why I've chosen to use 22K because if I was going to connect this up, marry this up to an amplifier it was going to be one of these ones. Because they're the ones I think are the greatest ones if you want to build them. I mean if you see it's about wanting to build a little amplifier that's easy to build. This is the one to go for because it sounds really, really nice. Now even though it's asked for 24-0-24 volts going in I can only provide it with 22-0-22. So I've got to work with what we've got. I'm going to be using the old Digilent Discovery, Analog Discovery 2, to take the measurements of this. Alright, let's do it. Okay guys, so we're going to just put some power in on this. We've got some power. We'll run our waveform gen. Let's go running already. Let's just put this around about let's say 2 mini-volts. We're going to start just turning up the volume. So our input volume all the way up on the potentiometer on this. And I'm going to start putting some actual input into it. So as you can see we're going up and up and up. Yep, we're going off here. All I want to do is just have a little look and just see what sort of input we can put in. Now the highest I can go on to this is set at 1 times, it's 5 volts. Which I think should be enough for a pre-amplifier. We can see we're clipping at the top. Let me just, a bit easier to see. Now you can see there, look, clipping at the top. Which is good, that's the good clipping. We like that sort of clipping. I'll give it a bit of extra, you know. All the thumb seems to be bottom clipping, not very good top clipping, better than bottom clipping. Yes, you can clip top first, that's better apparently. So we got that first backer off. There's no clipping and we can see on the FFT, look how bad that gets. See on the FFT, we know all that drops down. Okay, we're good. We've got about 13 volts there, RMS. Peak, 37 volts and 37 volts, that's pretty good going. So let's just tighten this up a little bit with this. We can see we're 0.8, 0.7, minus 0.8, 0.7, not 1 on there. We're into minus 70, minus 78, minus 71, minus 79. Minus 82, 83. So this is all very low down there. The noise floor down here is really, really low. I'm talking like 110 plus, which is pretty good. That is good, isn't it? That is pretty good. All right, so let's just back this down a little bit. Let's say we keep it round about there and swap this back to, let's say, about there. We'll do a sweep. Just have a little look, what it looks like on a sweep. So here we have it, sweep there. We've got one volt going in here. We could probably make that just look a bit bigger by dropping this down to one volt. It's probably a bit far extra from five. There we go. We've got two volts on here as well. And so we can see what we're looking for is, you know, does it do anything here? Does it fluctuate on its amplitude? I mean, it certainly doesn't. It does not. Not even in the tens of millivolts, it doesn't. Richard and I know it's not apparent, but it's nice to look at. It's nice to look at. So, well, that's that. That's all you can do really. I mean, I can connect it up to something to have a little listen, and I'll do that. But I'll do it in another video. I don't know, it's like, but these videos get too long else. It's just no good to be in too long. Let's put this back here to that same there. Let me have a look at that like that. So, looking all the way through this lane, it looks pretty good. It's pretty good. Yep, that's it. I'm going to wrap it up. If you got this far and it was interesting in any sort of way, that's brilliant. And thanks for watching and I'll catch you in the next one, guys. Bye-bye for now.