Elekit TU-8450: The Ultimate Guide
The all-new Elekit TU-8450 Valve Pre-Amplifier Kit is a vacuum tube preamp kit that incorporates a solid-state phono equaliser stage, accepting both MM and MC inputs.
This video is the complete guide: covering the unboxing, an overview of the kit, the tools you need to assemble, the build itself, and finally testing.
Elekit TU-8450 Tube Pre-amplifier Kit with Phono Stage
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AI generated video transcript
Guys, Nick from HiFi Collective here. Today I'm going to be unboxing the new TU-8450 valve line level preamp with solid state phono stage. So this is replacing the 8500, very similar format, very similar size. The 8450 is finished in black. So it uses a 12AU7 on the line level. You've got three line level inputs, RCAs. You've got one 3.5mm jack input. You've got one record out and one preamp out. So the record out, you can record, or it could feed, I don't know, kind of a subwoofer or something like that. There is room to change the decoupler cap. They've got big space on the board for that. So let's open her up. I'm going to do a video as well where we build it. Always very straightforward to build their kits. They're a joy to build. So here we go.
We have the instructions in English, always useful. There we go. All the various boards. They are using stickers for the, so describes what you're controlling. There you go, some stickers, various boards. Everything comes in nicely packed bags. So this looks like the hardware bits and bobs. All the valves have got screening can covers, which is always good to keep the noise down. The components, some knobs and the resistors. Here we have, that's the mains transformer. Oops. They do provide a Japanese plug, which is not really used unless we're sending it to Japan. So empty box. A quick scan of the chassis. It's black painted steel chassis. So this is actually the size of it, so it's not too big. It goes really well with the, which one does it go well with?
The 8400 amp, but you can use this preamp with any of their power amp kits. There we go. So that will come apart quite nicely for the build. Right, so let's get on with the build. First things first, let's talk about what tools you need for the construction of the kit. So soldering iron, solder. I always use the Silver Gold Mundorf 3.8% content. Scissors, Stanley knife, nut runners. Well, you can use the spanner if you want to. A file, probably for filing down the joins on the PCB. Pliers, tweezers in fact, for applying the stickers, though you don't really need those. Pozidriv screwdriver, cutters and pliers. So as you can see here, you've got the boards. Now they're all kind of together and you have to very carefully snap off all the different sections.
The way to do this is you pop it over the edge of the table. You can see where it goes through like that. And then with the file, you take these off. I mean, I probably won't do that. And then there's another bit of it. So there. So you're just getting all the PCBs kind of ready because that's what you're going to do initially is the PCB. So we have two boards here. That one is, this is the power supply kind of section. One is for the 115 volt and the other one is the 230 volt. So being the UK, we're going to use the 230 volt. So let's crunch that like that. So disregard the 115 volt there. This one. Oh, this is, so this is a hundred volts. So we don't need that one either.
So let's get rid of that one. Like that. We don't need that one. This is the back of the, what you'll, you'll see this at the back of your preamp. Once it's finished, this one, this one there, and you've got this board here. That looks like there's two versions of a volume control board. There's one here as well. It's a spare. It says that brilliant. So I've got all the boards ready and then let's just have a quick flick through the instructions. So very easy to follow. First page gives you a bit of an intro. This kit can be used for moving magnet, moving magnet and moving coil.
It gives you a list of the tools required and then just a breakdown of all the bits and bobs, which you're quite, it's up to you if you want to go and check them all, but they're usually very, very good and they supply everything that you'd need. So there you go. And then it talks about the PCB assembly, which we'll crack on first with. As you can see, everything is in its own little bag. You can't really get confused. Say like the resistors all have their band, the colours on their, on the bodies. So refers to what colours you should see to know what the resistor value is. You've got some diodes here. Caps obviously have what they're called, the values on the side of them. And then you've got some chips, valves.
So they, we're selling the one that comes with valves. They provide the JJs, ECC82 or 12AU7. A very musical valve. I do like the JJ tubes. Then you've got your feet, you've got your switches and your connectors and your volume control there. Heat sink, IEC input, RCA connectors there. You've got your valve bases. These look to be belt ons. Yes, they are. Screening cans to keep it nice and quiet. Volume knobs, on-off knob. And that's pretty much it. So here's the mains transformer very petite. It's an R-core, superb, very efficient. And then the various stickers and things. So we're going to get the soldering iron warmed up and we're going to get soldering. Right. So I have built all the PCBs for the, for the kit. So I'm just going to give you a brief summary of each PCB.
This is unit two. So you can see here that the only thing you need to be careful of, but there isn't much really because it'll only go in one way. So this is the, the volume control sits on unit two, just fits in, make sure it's flush, which you've done, done that and put the nut and washer on there. So that's all complete. Board unit, what are we on now? Unit three assembly. So this is, it looks to me to be the line level stage of the kit. You've got the resistors. Now they provide a color code for each resistor. Ticket offers you go along if you want to. I always like to measure them up with the multimeter just to make sure they're the right value. Very straightforward. Make sure the resistors sit flush to the board.
There's Zener diodes that are fitted on this one. There's one there. Obviously the, you've got the cathode and the anode are marked. That's with the black line. So you can see how it looks on the board and that's how it should be fitted. And you've got the actual brackets for fixing the nuts on the PCB. So that will only go in one way. The solder points at the other side. Pretty straightforward. You've also got capacitors on this. These are electrolytics. The negative is marked by the line, which you'll see on the board. Straightforward enough. Get them the right way around. Otherwise they'll pop. With the Belton B9A basis, that will only fit one way around anyway. And then you've got the method of fitting the actual skirts for the screening can. So yeah that looks great.
Just make sure your solder joints are good or good. That's that one. Then the big board is the unit one, which is this one. So lots to think about on this board. You've got the LED's have to go a certain way around. Where's the LED? Which is here. You've got the anode and cathode again. So just that will just show you which way around to do that. So be careful with that. Resistors. Same again. I've got the color codes. Make sure you get that right. Zener diodes. The cathode is marked by the line. So make sure you get those the right way around. The electrolytics and negative is marked on the board. Make sure you follow those. With regards to the chips, you can see the extended bit there. That's marked by a white line.
The connectors go in only one way around. So you can't get that wrong. You've also got the rectifiers. Yeah you have to follow those carefully because you have to get them a particular way around. Same for the transistors. You can see the half moon kind of shape. So that follows the body form of the actual transistors. The relay here only gets, you can only fit that one a certain way around. Then you've got these caps here. They can go any way around. That's fine. With regard to the fittings for the op-amps, they have to go a certain way around and it's demarked by the crescent moon there and the dot there. So that's for fitting the actual op-amp onto the socket. What else have we got on this board that could make you go wrong? That's pretty straightforward.
Hardware is straightforward. Make sure everything's flush. These caps here can go either way around. So that's fine. That's it. You've got on this one, you have the actual button switch there that fits from underneath. So that's all done. Cool. That's three. So that's quite extensive on that one. Three there. Then we've got the AC inlet unit, which is this one. So make sure that you're using the 230 volt. We're in the UK, so use 230 volt. They provide two other boards for those who have a mains voltage of 100 volts AC and 115 volts. So we're not using those. For this one, the switch can only go in one way around. The fuse holders have a clip, so it holds the fuse in place so it can't slide. So make sure you get those in the right way around.
The connector is pretty straightforward and then you've got the IC there. That's that one. For the other boards, you've only got unit four, which is the front unit. It just has the actual brackets for M3 connection onto the actual chassis. So that's cool. There's no soldering done on that one, which is what you'd see at the back of your preamp. So that's all cool. So we're now going to get on with bringing this all together for the fit inside the chassis. Before you do that, you might want to just have a quick look at all your soldering joins. Make sure you haven't missed anything. Make sure there's no straggly bits connecting to it so you don't want connected. All looks good to me. All right, so here's the hardware bit. Cool. So we're going to get on with that.
So I'm bringing all the boards together. I'm at number 45 on the instructions. So this is bringing the volume control board onto the front panel here. So you can see the diagram pretty straightforward. You have to take the washer and nut off, pop it in there and that fits in place. It won't move around and then pop that on. Just need a pair of pliers to tighten up the nut. There you go. That's that done. So we're now fitting 146. Unit four to unit, this is, where's unit four? This is unit four to unit one. This is unit one. Right, so you've got like that. So this is the selector switch. You have to take the nut and washer off here. So washer. Yep. So it pops in there like that.
Let's put the nut and washer on and don't tighten it yet. And then there's two screws to go in. Where are they? Remember use the right screwdriver for the job. So that goes in there. There's another one. There's only one. And then tighten this up. Right. And then we're going to have the back panel here. So that is what you'll see at the back of the preamp. So that will fit on. So you have to, you see here you've extended this with a metal stainless steel thing that goes through that hole. That goes through there. And then you've got the ground goes in there. This is your things. There's lots of screw holes on there. So these are self tappers. So the black screws and how many are there? One, two, three, four, five, six, six of those.
Let's do this quickly. Right. It's done. So that stainless steel shaft is through the hole there. That's changing it from moving magnet to moving coil. And then we've got a bit soldering to do here onto the board. So you probably noticed that my I'm using an Antex soldering iron. That's because my well has broken. So, annoyingly, so these are using these jumpers. So gauge what they are, the distance and shove them in. There's five to be fitted here. So this is connecting up the volume control to the main board. So I must sing the merits and praises of an Antex 25 watt soldering iron. I used to use these for many, many years. They always do the job and pretty cheap. Which they are about 30 quid nowadays, aren't they? Those leads. I want to make them nice and neat.
So I'm going to raise them up so they're all level. I've got a feeling this is the last bit. There is more bits of soldering. Boom. Done. Next bit. I'm going to be fitting unit three. Let's have a look. So there's a standoff required, which is this one. It's got to be that way, isn't it? Make sense? Great. Just slips in there. Screws. There's the standoff goes through this hole here. And then we're doing blobs of solder here. So turn it upside down. Solder these terminals, 80K, the total of 22, total of 22 locations, including the backside. So right. So you have to solder all the way along there, all the way along there. So you have to get the angle right on the board. Well, the soldering iron. So leave it for a couple seconds. That's done. Right.
Pop that back there. Now I've got the chassis, the screws. So what are you doing? Stretching. I'm going to put the feet on. So these use the M4 times eight. So these chaps, feet are on. Main transformer. So this is kind of, there is an orientation to this. You can see the black wire goes to the back. These go to the front. So what do we use for this? M3 times eight. Quite a small transformer. There's not a lot of juice in a preamp. Don't do them super tight yet. Get them all in first. Now we're tightening them up. Right. So now we're fitting the AC inlet that way around. It goes, pops through the hole there. Nice and flush. So self-tappers in falls. Looking good. Got two of these. Going through the bracket. Made a mistake.
I'm going to go back in a minute. Let's get these in. So at the rear, you've actually got this just on the back. This gets fitted there like that. So I'm going to take these out. Well done, Johnny. Johnny just pushed that to my attention there. Right. So now we're going to pop this on. So this is the rear panel. These leads out the right. Good. This bit needs to be external. So it's like that. Okay. So it's like that. When you're building these kits, just take your time. It might appear that I'm rushing it. I suppose I am, but I've come up with a couple of stupid things I haven't done right, but easily rectified. Last one for the rear. There's another one there coming up through the bottom. Cool.
So we're now on 56 and it talks about connecting up the mains transformer. So that connects to that. Nice and easy. This connects to that bit of stretch. Yeah, it goes over the top. Put the valves in. So they provide the JJs, ECC82s. So when you're fitting the valve bases, you can see there's a gap there. Line that up with the gap on the base. Skirt makes it hard to see, but when you're putting the skirts on over the top, to that bayonet like a light bulb. So make sure the top of the spring goes on the top of the valve. Find the, and twist it. So this protects against noise from outside. Right, now we're putting the other bits on it. Right, so there's a groove here that that wire goes through. That's it. There you go.
So you line up the holes here, the washer. So got my fingerprints over it. It says it wants you to use the back of it. There's two screws going in and they use these washers here. Let's do this, they ask. Longer screw, longer screw. That's a cover. And then you've got the front here. It's got a hole there. That hole goes that side. So you're using the screws with the washers. Great. There's another claw one in the middle. Great. And it says put the knobs on. So this is a D knob, D shaft for the volume control. Put a push on. And this one is same again. A D, push on. All that remains is putting the stickers on. So warning label goes on the butt.
I'm just going to give this a wipe because it's got fingerprints all over it. Sweaty. So just a bit of soap washing up liquid on a bit of a sponge. Give it a wipe down. Drives up pretty quick. Just wipe it down there. Because when you put the stickers on you don't want any grease to take away the power of the adhesive. Right. There we go. So the warning label goes on the butt. Okay. Still a bit wet. Hold on. Just line up a bit. And then the front. I'm gonna give that a wipe as well because that's a bit fingerprinty. They do provide two of the same sticker. I suppose just in case you mess it up. So at the top you've got the volume one. Oh actually they're identical.
It's just whether you want to have the black on gold or gold on black. I'm going to go for gold on black. I'm not a fan of stickers. You could use tweezers to put this on straight. And there you have it. Finished product. So I'm going to wire her up. Make sure there's no issues. And has it got any test measurement points? Oh yeah cool. So and then after I've got it up and running I'm then going to go through the checks. Because the way they could do it they kind of think right well you built it. You've done a really good job. It's going to work first time. So we're going to make that assumption. But once we get up and run in I'm then going to do the test just to be sure. Right. So she's all built.
All great. I'm going to turn. Moment of truth. I'm going to turn her on. So this is the TU-8850. It's on full volume. This one obviously preamp. You just turn the volume down right. So it's zero. And then get it on the right selector. This is on line one. Which is that one. With this there is a relay. So you turn it on. This is going to flash three, four, five, six, seven, eight. Anyway a few few. So I'm using the EFI DAC. Yeah. And then the glass house kit speaker number one. So when it stops flashing it's going to play and you'll hear a click. Oh did you hear it? It's a click. So okay so this is a non copyright tune so don't judge me. Okay. I don't even know what it is. Okay so terrible.
But now that I know she's working I can hear she's central. I'm just going to go around and test all the other inputs. Pretty straightforward. You just move your input cables along. Now just to test the actual 3.5 mill jack input I will fit the lead onto this. So it behaves like a 3.5 jack and then shove it in there and then move it to four. We've got two tunes going on at the same time. Anyway you get the point. I can't test the the phone though because I don't actually have a record player here but I'm going to take it home and I'll let you know. I'm sure it's going to work.
But next we're going to do take the lead off and there are some test points so I'm going to get the the meter on it just to make sure everything's running correctly. Anyway there you go. Build it. It's brilliant. Okay so we're going to take the tested preamp and it works fine as far as I can hear. We're just going to take it apart so I can actually test the points, the test points on inside. So three screws at the bottom for the front. Don't worry that's water because I just gave it a wipe. It's not leaking don't worry yeah. So I can go there and then these four screws, side screws, lift the lid off. Cool so there we are. Now if you go to page, the page number is it? So the back, yeah it's page 23.
So there are 17 test points and as is always with this case is you've got to find the test points. So I've got my trusty multi-meter here. I'm going to use the earth point at the back which is basically attached to that ground. You can see it says ground. Excellent. I'm going to plug it in of course. Obviously be very careful when you're doing this. Yeah switch her on. Flashy flashy internals. Okay right this is where we hunt the symbol to try and find the test points. So 1R, 1L. It's going to be here somewhere. All right I've got to wait till it stops flashing, stops flashing now. All right great. What we're doing with this one. So one R is there and it says it should be five millivolts for mm. What are we set on now?
This is mm. That's mc. Does that change? Yeah it goes up. All right that's such a low reading. I don't think this is gonna let's do a range on it. Is it accurate enough this? Okay so you got better reading there and there millivolts. Yeah and then two L fourteen and two R which says low value. Great, that'll do. Right, three. Let's just auto-range it now. Cool, so three. 0.3 is there. 11.245 and it says it should be 11.5. That's pretty close. Four is minus 12. Yep minus 12.062. Five L five R is four volts. So this is all the phono stage this bit I'm testing now. So five L. Johnny can you see five L? I don't think it's anywhere there is it? So it's on the up upright. So five L there 3.74.
It should be four volts that's fine. So that's five L and five R should be like a mirror 3.88. That's great and then six L and six R should be 70 to 78. So six L that's 80 close enough. Similar. 76 there. 80 there and then seven L and seven R should be a bit two volts higher and then we found eight and that's exactly what it says it should be. Nine is 160. Ten should be 180 but that's kind of 10% up isn't it? 11 is zero. Yep pretty low. 12 is 12 is five that's good. 13 is five as well. Yep and then 14 is 12. 14 is there. 14 should be 12 volts which it is. That's there. 17 yeah great and then 16. 16 is there. That's correct and then 17 the last one.
Yep all great. All right great. All good. So quite happy with all that. So brilliant. Great build. Ciao. Just before I sign off I want to say a big thank you for watching our videos. Like and subscribe and follow us on all the social network platforms. See you later.