 Hello everybody, happy new year and I hope you've all had a great break, lovely little coldy and welcome back to my channel. So on the bench today we have something that I've not had on. My bench for quite a while is a little tube amplifying system. Now this I found on Aliexpress, pretty cheap the way it is. It's based on a 6k4 tube system and it's quite easy to see on an express. I'm going to show you now. I'm not going to go over it too much in detail on here. You can always take a peek at the link. I could always stick a link in the description, I think I will. And you can see there look, you get free shipping and all sorts. Now it says here that the power is 12 to 16 volt and it's DC. I was actually looking for one which was going to be the same as a YouTube friend, Sonny Cox which was a 12 volt AC system. I've got the wrong one but I'm quite happy with what I got here. So let's put it back up. One of the things to be noted about this is it comes with this acrylic case. Now I didn't know that. I didn't know if it came with a case or not, but there's a very good reason why it does. And the reason is this, is that when you're putting 16 volts into this, you're getting around about 135 volts from these two points in here. And I'll demonstrate that in a moment. And so if you were to have this without the case on top and bottom and you had the power in and you were just playing with it in your hands, you get yourself quite a serious belt off this. So there's a very good reason why I've put that case there. What can I say about it? It's not bad. It's not bad. I did take the liberty of upgrading these tubes to the GE 5654s. 5654Ws. There's a noticeable difference and I do prefer these to be in. But first of all, we're going to have a little peek at it with the way it is. Now let me just move that if I can. So I've got my probe set up here to a couple of 1K resistors coming out of each channel. And one of the things to bear in mind with these is you want to make sure that you've got a clean supply for it, clean DC supply for this. And you also want to make sure that your audio player, remember I learned this a long time ago, is you get in, if you put crap in, you get crap out. So if your source isn't very good it's not going to help you at all. You're just going to amplify whatever noise and everything you get resource. Use shielded cables because it's going to pick up noise. This is a class A system and so it's basically just permanently on and open waiting for signal to go in there and it do its thing. It doesn't have like a small quiescent. It has basically just full on all the time. And if you do taps, you're going to do a demonstration that you're going to get noises coming off these things. So let's have a little quick look at the, we're not going to go too much of the circuit. I'm just going to tell you how it gets there. It's got a DC to DC converter. I'll tell you how it gets to its high voltage. DC to DC converter here, which is a step up or step down in this configuration. It's a step up converter. And there's an IRF640 there which enables it to get that final high voltage. Like I say, which comes out here that goes through the system. I think it's got about 70 volts per side. There's a little switch here. I'm not quite sure what it's for, but it does make a sort of difference. You've really got to listen for the difference on tone. It's, and this thing, it's supposed to be a up plus. Here it's, I'm not quite sure. It doesn't actually do a gain gain. You can't really hear it, but in this side it says it's sort of like high five. All right, so we'll just leave it there because that's what you want to hear anyway. It's the high five sound. So what I'm going to do now before, before we do anything else is I'm just going to show you this voltage. So look at me the way you see me to here. And I'm going to plug this in. Now for this I'm using battery. And hopefully you're going to be able to see what's going on over here on the battery. There, I've got the timer in the middle there, so I can't see properly, but we'll put that like that. Okay, can you see that? So you can see there, I've got 15.7 volts. I'm going to turn that round a bit better. 15.84 volts. And when I turn this on, we're going to be putting our voltage into here. So if I just move that up a little tiny bit, you see that's around the medieval range. Let me just see. Put these on, but we don't want to be completely in your way, do we? There we go. And I'm going to pop that down onto that pad, that down onto that pad. And I don't think we've got to arrange the, oh sorry, what am I doing? It's supposed to be DC. Yup, that's just me being a bit, being a bit daff, so we've got minus 200 millivolts. Let's get that down there and click on down there. There we go, we've got 133 volts. 132.9, 133 volts. The merits minus is just at these probes of them all around. So you're going to be very careful with one of these. And that's why I believe that you get the acrylic case with it because it's down for the safety. All right. And as you can see actually, we can point out some good stuff here, as you can see, we have got over here 6.6 watts, 6.7, 6.6 watts. So it sat there at 0.43, 0.42 of an amp. We need to keep that in mind because when we change these over, which I'm going to do in a moment, I've got to, in order for me to set up for audio, we're going to have to do that last, or I'm going to have to do a little, right, we'll put the audio in here and then carry on and do the tests just to see what distortion we get and what we don't get. But just for now, just to keep this running the way it is, we're going to do those tests now because it's set up to do the tests. What I've got here is a little one probe on me. Let's put that out there. I've got one probe here on one channel, another probe here on the other channel and we're going through, we're going through our analog discovery too because it does work quite well, in actual fact it works fantastically well, I really do like it. We're going to switch over to the screen again. We're going to take a peek at what we've got going on, on there. All right, so at the moment it's doing nothing. Now I'm going to be feeding in the signal from my little music player here. Thank you very much, John, again, for supplying these particular soundtracks. In actual fact, I think that's one that I've done, 1K 4.5, with a, in actual fact I can have a little look at that series worth. Notice Nick compared to John's. Now the nice thing about this is I can actually turn this up to full blast, which you're going to see me do. I'm going to put it on full blast and I'm just going to click on run over here and keep turning that up. Now you've got to remember that I haven't actually turned up the thing yet, actual preamp. So let's just leave that down there. That's going in a loop. Let's start turning it up on here and we can see what we've got going on now. Let me just turn it all the way. That's full on. All right, that is full on and as you can see it's still using the same amount of current because, like I said, it's permanently on. I don't know if that's going to make any difference it being there. It doesn't seem to be. So it's not as low. It's going to go up in power as we turn it on. It's on full power all the time. I don't know if you can see that because I can't see it on the screen because it's got the timer in the way. So let's have a look at what we've got going on here then. So here we have our, this is our fundamental that we're putting up and this is our two kilohertz and this is the 1% distortion. Now, as you can see, we don't have any clipping over here. If I just adjust this to that, you can see there's no real clipping. I might say there's a slight rounding off there. So let me just turn it off and just see if that makes any difference. Not really, but what you may be able to see is this. On the one side here, we've got ACRMS, I'm going to put that on full again, that is on full, ACRMS of 394.75 millivolts and on channel two, we've got 415.32.31. 1.1 volts peak to peak. All right. So that's interesting enough. And if I just make this go a little bit more like this, you might be able to see there is a little bit of a difference here as you can see. They're not quite on top of each of them perfectly. We just fair enough. I mean, you're not going to get that absolutely perfect anyway, I wouldn't have thought. But the thing to see here is that we do have on our third harmonic, he's slightly lower than our 1%. So still not too bad. If I just adjust the volume down a bit, see if we can take that down to, we will be taking out quite a bit of the input, but there's from about three quarters of the way down, there's not a lot of change on that. And what we can do now as well is just what we've got that like that. I'm going to adjust this into the top line. It goes just underneath the bottom there. I'm going to adjust this to let's say 500. Like that, because what we want to do now is just keep an eye on this top line, this bottom line. Slightly over there, slightly under on the yellow trace, slightly under on the yellow trace, slightly over on the blue trace and just exact on the blue trace. What we're going to do is we're going to switch out and go for a, and go for a, sorry, trying to find it on here. We're going to do a 20 kilohertz to 20 hertz, 20 kilohertz sweep. I'm just going to find it and we've got a hundred, 20 to 20 kilohertz sweep. So let's put that on. And what we're looking for is any real loss in amplitude, why we're doing that. And it doesn't seem to be, it seems to be pretty good just before that gets too tight in there. It's just been a bit bigger. So we're still on the top line and just over on the bottom line. Everything seems to be staying pretty okay like that. And in a second, we're going to go around. Okay, there's not a great deal going on there. We're just going into about 13 kilohertz now. 14 kilohertz. We can see on the peak to peak here, we have actually dropped down very slowly on channel one. And that is on that. No, no, no, sorry. Ah, it's because I adjusted it so I should shut up and put it just back down to where it was. I'll keep them both on the one there. But it doesn't seem to really a great deal of change, which is pretty good. That means it's got a nice constant all through the frequency range. And it won't be going up and down in amplitude. There's definitely nothing untoward happening there. So all right, what we're going to do then is I'm going to leave that like that now. Let's just go back to this. I'm going to stop that and stop this. And I'm going to change out these tubes. Now, again, just take note here that we've got 6.5 watts that we're using there in power and it's 0.42 milliamps. They're 0.420 or 430 milliamps. So we're going up to that half amp thing, 15.6 volts. Right, so I'm going to turn this off. I'm going to disconnect this. I'm going to very carefully take these tubes out. I'm just going to leave this running. In the back there, it's going to make no difference. There's no amplification. I just don't want it to switch itself off because it gets a bit annoying and we're going to keep going through that. Let's put that there. The tubes are quite warm, as you'd expect. Because they need to be able to get hot enough to send the free electrons up to the top plate. Yeah, to send the free electrons up to the top plate. I mean, it's got to get pretty hot to boil them off. That's where the interest in physics comes in when you understand how these thermionic systems work. It's very interesting. Very interesting. And the experiment that went behind it as well, which was then just ignored. Okay, so I don't know if I put that back there again. It doesn't really matter. I could leave it up, actually. So let's plug back in again. I'll really do that just for the sake of safety. Now we've got our input still going in and we're still on 100% on the volume. And that's still running. We're going to put it to 1%. There, these ones are actually John's. I'm going to put it on John's. Let's put it back on mine and we'll look at John's. I mean, let's see if there's any difference. I did it on exactly the same thing, but different sound cards and all that. So now we're going to turn this on. One of the first things we're going to see, of course, it went up to nine watts there as it's cold, but as this starts getting warmer, maybe you can see that we've actually, we're not using as much power with this. We're not using as much power. So let's just get a few seconds. I just get this set up over here. Start running this again. And you can just put that there just in there. We'll just turn it off for the moment. All right. And I'm going to start turning this up. Go up and up and up. We're still going now. Now we're about a little bit over what we were with the other tubes. I'm going to still carry on going up, up, up, up, up, up. Still no clipping. And this time we're on two volts peak to peak on channel one and channel two. This time we've also got 0.7 volts, 0.72, 0.73 volts here. And if we look at this a bit more closely, we can see that these are pretty much on top of each other. Now these tubes claim to be matched. And what they mean by matched is basically there'll be a whole batch of tubes and the bigger sample amount of tubes you've got, the better of course. So you're using a special tube meter. You can match up all the characteristics and ensure that when you send out a couple of tubes, they're pretty much the same as each other. And that means that you then end up getting this, where they are both clearly very close to each other. Hardly anything. We're talking, well, we're talking less than 10 millivolts, not even 95 millivolts difference between them. And as we end up having a lovely, a lovely output like that. So let's put this into this and we can have a look at this. So this is our 1% here. And our 1% is at a 60 dB, minus 60 dB down. We have a second harmonic there, which is that warm sound. And that is at 53, 54 dB down. Nice. And our third harmonic there is 73, 72. So you're not going to hear any of that. You're not really going to hear this 1% here either, minus 6 down. But it goes to the show load, doesn't it? That you're going to, out of these tubes, you get more power. It's got less distortion for what you're actually getting from the tube. And yeah, the GE ones do seem to be a lot better than those 6K4s. Just this down here. Yeah, absolutely lovely. And there's nothing untowards in there, it seems. That should show these for being bad, whatsoever. I think when they talk about these tubes, and they say that, John, is it there here? Only the best tubes are slipped by a river and they're used as match pairs. That's how I bought these as match pairs. They're military grade, ruggedized military grade, because oh, I forgot to show you. Maybe when we do another video. Oh, I could just swap them out. But what you'll find is, do our little test. So if you look at the FFT down here, what you're going to look for is noise. You can see the blue line going up across the frequency there. That's on the right-hand side channel. You see the orange line going up a bit. And then on the left-hand side channel, the blue going up a bit. No, it's just with little tiny taps off this. And that's one way of having a little look and seeing how these tubes are doing for noise like that. Now, let me just, we're going to leave it like that actually. We're going to put a stop on that. We're going to turn this all the way off. Disconnect this, and I'm sorry to go through this again by putting these the other way around. But I'm going to swap these back out again, because I'll show you what the noise is coming off the other ones. It's going to be hot. I did actually make myself a couple of little things for pulling these out so I don't burn my fingers. Let's pop these back in. This is the last bit of this. We'll have to do a sound on a different one. I suppose we're going to skip through these bits. I'll just get a bit of a sound check in. Okay, so let's get that in nicely. Once again, re-power up. Turn that round. And again, you're going to see that when I turn this on. It's 12 watts when we first kick in there, and then we settle down at about 5.7, a little bit higher, 6.7. Now, let's just get straight on with it on here. And we can click on run, because we have some power going in. Let's turn this up again. So there's our peak. Now, when I do, this should be the blue tube. You see the difference there. And then the yellow tube. And you can see how that jumps up and down there. So there is a difference between these ones. And you can hear it in the sound as well. There's a difference between these ones and the other ones. There's not so much movement on the other ones, where there is more on here. These use more power. They don't give us much output. They got what I would say is more distortion, especially on that third harmonic. Third harmonic, you can see the differences as well. Let me just get rid of that for a second. When you look at the FF-10, you can see the difference here between this third harmonic on one channel and then on the blue channel on the FF-10 side. This has got a lot higher order there on that third harmonic there. This is our second harmonic. This is considerably higher now than what we're putting in there, which is at 4.5 kHz, 1%. And I don't believe you get as much output anyway. I think we are on 21 on the output, round about 5 dB better on the output than on this one. So there's the difference between those tubes. Anyway, thank you for watching if you've got this far and I'll catch you in the next video guys.