 Hello everybody and welcome back to my V-Log, to my channel, here on the bench today we've got another amplifier circuit. The game's been bought from AliExpress and this one I have high hopes for. This is the Quad 405, this is the T03 version which is these transistors rather than the normal 220s and the 264s, I think they are, but correctional people get that wrong. Transistors and it's from an old Quad, it's an old sort of 70s 80s British design, this particular one which again has been taken over by the LJM, the other sort of one I just had with this is you can't get circuits for these, there's no circuit diagrams, apparently you don't get them with any of them so I've got an apology to make now because the circuit diagram that I put up on the MX50 SE is not the correct one, it's the one that comes on the page when you buy it but I did a transistor check once I saw written that you can't get these circuit diagrams, I did a transistor check as the easiest way for me to see whether it was the correct circuit or not and now there's a difference of one transistor, I can't remember which one's got it, whether the circuit's got the one extra or the schematic has but that means it's a different schematic, so I apologise for that. I'm going to put it up on the screen now so we can just have a little quick look at the advert for this of Aliexpress and we'll just have a quick few moments on that. So here it is and it's there and it's all its glory, it's a different colour, yes this says it's the upgraded version 2019, I'm not sure what the upgrade is, it's possible, it's got this thing on the back of it all and now everything's going slow here, that they've got a capacitor there, I don't know whether that was there in the original or anything like that, I'm not that familiar with these things, it looks like it can go from 30 to 50 volts, I've got a 32 volt input on it at the moment, I'm not going to push it to 50 volts because I don't have the ability to do it at 50 volts and we're not going to be doing a full power test at 50 volts anyway because I can't do it and secondly it doesn't really matter, it doesn't really matter at this stage but we can look at its frequency response, I don't know why they've not put it on the zero line, this is just the way they've had 10 dB at the top and plus seven down at the bottom on their screen but if we look at this and say that this is a linear scaling down here, we can sort of see that, well I'm not quite sure what we can sort of see but that would suggest that that's like a half dB and this is a one dB I think because that's seven eight that's eight six, seven six and eight six so you could sort of say there's one dB difference there and then if we were going to do sort of half of that near enough we could have half be different from the top and that's that one dB difference I think that's what it's trying to show, this is a 15 Hertz but look what it's going to be like when we do the performance tests on it in a moment could be completely different so here we have our fundamental nice low-level noise floor which is all well and good and that's it so this is this what you get this is the actual they sent out to me the blue one it comes with this bit of heat sink in here if you choose for it to come with a bit of heat sink in I'm not sure whether the chips are originals or not or genuine I should say as possible they are possible or not I've actually put genuine chips in just for the sake of it and the inductors seem to be measured on a decent inductor measuring thing so let's just get out of that and do some tests because that's what we can do really we can listen for the sound of it but at the end of the day that can be very subjective and then numbers don't really lie so let's pull up our waveforms let me see we can get them both up and I've got it set up a minute for one kilohertz gain in run zero volts and we're not running at all and we've got our RMS there AC and our peak-to-peak values are not what they seem I just wear it with switch stuff so that's just gonna jump around a little bit so we've got our voltage on everything's on as it's supposed to be let's start with the test hit run we'll start up in a signal coming in now at the moment on ten volts per division down here but I'm in ten times which I shouldn't be on we should be on one times so let's start bringing that back in look off the reference voltage to about 20 and start bringing that in as you can see now we have these two distinct quite low down there so look where they are quite good on there minus 90 minus 70 just move this up slightly just drop that down to there so the attenuation is there I can't go any higher on the five volts thing which I think I may have to switch over to ten times anyway but we'll soon see as I start going up on this I'm just gonna go into clipping so you can see it yeah I'm just gonna back that off now this could be clipping because it's going off the screen as always that we're gonna see if that's why it happens there's a possibility that's why that's happened so I just need to flick over to ten times on my probe look over to ten times here you should really set that up properly and we can continue going up because now you can see they're clipping there just back that off so really just out of the range of the clipping clips at the top first before it clips at the bottom let me see if I can get a bit more of that on the screen just bring this down and we're using 1.2 amps let's just pull that out there 1.29 amps and make sure just pop this across to five all right so that looks reasonable enough this is before clipping I'm gonna turn that off so we can take some pressure off the system all right and that's what we got over there so that doesn't look too bad at all I mean when you look at the FFT this doesn't really look too bad at all let me just shift this we can forget about that just for a second I don't know why that's just done that but let me just shift this up here we can look at that it's not quite at zero that's okay minus 78 minus 73 that's on our three kilohertz that's on our two kilohertz minus 72 that doesn't look too bad at all really does it no too bad at all and if we were just to look at this I really don't know how I managed to make that be like that so I'm still playing around with this software a little bit but that doesn't matter we can still see that we weren't really into any clipping situation you can see that by the FFT so just with our 31 volts going in there we managed to get 19.76 that's about 40 watts or so I would put the calculator actually just see what that actually says 19.76 we give it the 76 times 19.76 equals 319 divide that by the eight I'm right up we got on there okay so that's 48 volts 49 if you allow it to be counted up rounded up from that point point eight that's not bad yeah that's not bad at all and what we want to do now is we want to have a little look at it underneath the audio analysis software so I'm just gonna I'll tell that just to save that like that I'm just gonna get rid of that we're gonna here just start up our virtual machine this laptop's quite old probably about eight now okay if you can hear the funny sounds in the background it's my all of my cats has decided to use a bag that I had for delivery today as a bed I don't have a heart to kick him off it all right so the first thing we're gonna do is I'm just gonna take a peek at the frequency response and let's just actually give it a hit on spectrum analyzer we're gonna put a point to VRMS into there and we are gonna have a little look on the spectrum analyzer and just see what it gives us now that's on five averages so I'm just gonna turn this onto yeah I'll leave it on five averages and I'll just zoom through it for you so when we look at this it's fairly close this is at naught DB now if you remember the other one wasn't if you look at the top right under the screen in the orange just here it shows you the DB value and this is the frequency value and you can see from the scale down here as well the DB and from here is the frequency across the bottom all right so if I click that onto there we can see it's slightly higher but I believe that's just because we are at zero now not at two before all right well that doesn't seem to be particularly too bad there let's look at the frequency response this is what we're gonna be interested in we want to know how this thing goes from a low we're gonna go from 10 Hertz up to 50 kilohertz all right just we just want to see what it would do from there so I'm gonna run this or let's just put it on to one channel now point to the RMS that'll do and we can have done a bottom we're not going to need that amount so we have three four three there not the top we're not really gonna go above one DB maybe we can put just three there so we get a centralized image okay right so we get to see then it's I mean we have seen better performance from amplifiers that's for sure and this is a player says 20 kilohertz when I go across here we started off at 10 remember and we can say that we're 3db down because that's what this is is down here 3db down be further in fact but then we've got our this is at 11 Hertz this is at 13 Hertz this is at 20 or 19.9 the measuring of this is you know is what it is but we see we're sort of slight rise there in response and that's not saying there's extra base because the base sort of drops off and then we got a sort of drop off here and this is 10k now I did notice that it starts dropping off on the on the website there at 15k by the time we get to 20k but it doesn't seem to be particularly too bad I mean it's coming worse we're gonna do a THD the total harmonic distortion plus the noise and we'll do that at a hundred steps just like the last one and we've got an atome load there okay because there we have it it takes a little bit longer my end because I speed this up for you guys because I put this into 100 steps we got a bit more resolution what's actually going on and I don't know you can tell but when you see these here just see a bit better no idea what this is going on the background here this is to show noise and you see when it's all busy like this is when it has these little peaks and when it drops off you can see that it's not as busy and then it has a little peak of noise and it gets busier like over here but I suppose that's because of the higher frequency actually and it's not so much noise and I'll show you that in a minute because this is the total harmonic distortion and the noise so I'm gonna do now is I'm just gonna put it onto a total harmonic distortion and you get to see there you take the noise out even though there are some little busy areas still these little tiny peaks it's not doing too bad it's not doing too bad this is at 10 Hertz so that's still below 0.1 we all the way to the 10 kilohertz and it's all stable at 0.1 and it's only when we get to 20 kilohertz we're going to 0.1 or 0.1 I keep trying to retrain myself so 0.1 so that's not bad at all and I know we've already done a little power test but we might as well do that one to a hundred watts on here and we'll just do it in a 50 steps we don't need to do that in a hundred steps we'll just run that along pretty quick okay so again you can see down the bottom here we've got a 10 watt marker there you go from zero watts it's logarithmic not so much linear and we've got our percentages going up the side here and I always get it to cut off at 1% and that's where here it cuts off there at 1% and it's saying 53 watts we get to 1% and so it's really much on the mark for what we measured in the sine wave for the power output and at this voltage 32 volts so we're using 32 volts so I say that's pretty good too now this is going to be the one we're going to look at it on a scope now but we're not going to look at it in the sine wave we're going to look at it in the square wave and first of all we'll check out at 1000 Hertz one 1 kilo Hertz we'll just do a single shot on it that's what we need to see and we can see there why just get rid of that one on the next shot let's just do a single again just get rid of the blue line for confusion now this one indicates a small amount of trouble a small amount of overshoot but it's not ringing it's not doing anything dodgy if we keep it on the run we can see it's not doing anything dodgy very slight slope down very slight slope up nothing really to be too concerned with let's do a stop on that and let's just go down to let's say 100 Hertz we'll do run on that and there we can see that we got the bases start and drop off a little bit but not I mean it's not terribly bad it's not a great sort it's not great square wave is it I mean it'd be lovely to have this you know as a square wave all along I'm gonna let you know now that I've actually listened to so I didn't think it sounded too bad but I only listened to it on the bench here and things can be a bit subjective so and this is why we do it like this this is why you know we're looking at it like this because we want objectivity and not subjectivity now to me that again doesn't seem to be terribly too bad because it's from what I can tell here 0.01 volts down and probably need to find a way of working this out better yeah I can't I need to know exactly what this drop off here would really account to but as this is coming into the center line it doesn't look that great but you can remember right this is something I try and keep into account as well back in the day on 20 Hertz now back in the day 70s 80s let's just do a single hit on that that's not too clever is it I mean that's definitely not square wave anymore let's just give it a run no that's not square wave anymore but back in the day look from what I've learned is you could have had high fight back in the 40s but today's stuff that's pretty cheap will beat that then why because there's more consumerism you can build the things cheaper in order for you to be able to buy a pair of speakers that would have gone down to 35 Hertz back in 70s yeah give you a good representation down a 30 Hertz up to 30 kilo Hertz cost you an arm and a leg now you can buy it for a few hundred pounds you might a pair of speakers for a few hundred pounds and you can have that and the same with amplifiers to be able to buy an amplifier that you get you down at those low levels and up those highs and it will be balanced out nice with nice frequency response we're cost you an arm and a leg but these days you can get pretty you know you can get what you had then it's being really good today pretty damn cheap so I don't look at this and just think to myself well it's all a big fail let's just go to a 5 kilo Hertz now I don't see it as a as a big fail because it doesn't do as well as what some might think that it should don't know if you can hear the actual actual circuit whistling so I'm just gonna put on to stop and here you know you get to see this little bit of a bit of travel there but you still you know you've you've got the base being represented there these are quite you've got to look at a lot of these things to be able to work about probably but you get to see you know we're trying to keep square wave here for an old design but back then and I don't think that doesn't look like the greatest square wave that's a 10 kilo Hertz you know remember on its own thing at 15 it was like dropping off the side of a cliff so we're gonna hit it on 15 now yeah you know let's do it at 20 oh what did I do wrong okay so 20 kilo Hertz and let's go to 30 just see if you would have ever got there 30 yeah yeah yeah and that's at 30 looks like a screwy sinusoidal but there we go with you know you can't expect you can't expect these old circuits to give what some of the circuits would give today just because they're the older circuits and even though you want them to run quite nicely how the difference can be in there I'm gonna do a an audio test I've already listened to it I don't think it sounded too bad the natural facts from one I've been listening to over the last week the MX-50 I felt it lacked a little bit in there in the sort of the throttle clarity area was why I can hear with my other amp I couldn't hear where that was the first thing I noticed and you know you got to go into these things critical because if you don't if you're just thinking that you know everything's great then you got to be critical and you'll be honest to yourself as well and even though I like it I can just use it one transformer users less power the MX-50 it still lacks a little tiny bit that I could hear before and but it's it gives a bit of extra base and it gives a little bit of extra in bits but this is where it's going to get where people's own hearing because you can have all the sharing the same thing on the frequency response and over the nose but the amplifier circuit is going to sound different because you've got parts you got components on the circuit there's some of your resistors stuff like that make their own noise and so that's going to make a difference to what you get to hear at the end of the day from the circuit so it's all going to be down to what do you decide you'd like the best and that's how that's why I'm playing it for me it's going to be hard if you guys at home because you're going to listen to it through my microphone and it's going to come out of your speakers and you got to try and judge all this stuff and I'm giving you what I think is my preference I but I tell you now I'm on the flat level of I just want to go for is flat level I don't want any equalizing in there I don't even want any equalizer switched on and put on flat because that still adds let's say color or discoloration depends on your philosophical bent on that type of thing I just want mine to be as close as darn it to what the artist had recorded it at that's what I want that's what I want personally but everybody's different and that's the thing about these things everybody's different everybody likes to hear in their own way and but that's my bit so when I'm listening to it when I'm feeding back to you that's why I'm coming from that's my point on the ground where I'm coming from I want it as as as close to the source as possible all right that's it for the end of this it's gone away too long hopefully you got something out of it and I'll catch you on the next one bye for now