Beginner Stepped Attenuator Build
A quick one from Nick, showing you an Elma Jumbo build.
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AI-generated video transcript
Hi guys, Nick from HiFi Collective here. Johnny is away, he's not well. So I'm doing this on my phone, on my desk, so it won't be, the quality won't be as good as Johnny's stuff. So today I'm building a stepped attenuator using the Jumbo Elma switch. So with regard to all of the, those kind of the 47 step Elma products, they are discontinuing them. We are in the process of buying big stocks, so we should have some for a little while. So the beauty of the Jumbo is, you know, pretty straightforward to build. So you effectively will get a switch and then all the resistors, if you choose to do it as a kit, but you have to take them apart. So this is just one where I'm just showing you how it works with the board.
So this is the board you can see here. You, for this particular one, we are populating with the resistors sitting this side. So you can see there, all the holes are numbered. Okay. Now the massive thing with these is you do not want to make a mistake. You put a resistor in the wrong place. It is a real pain to get it out again. So what I generally do, I have the resistors all picked out like this. I know this is upside down, just ignore that. But basically it starts here. Step two, three, four, all the way down to step 46. So I picked the resistors. I'm kind of confident that they've picked them out the right drawer, but I'm going to check. Now the way I check is with my meter like this. Okay. Can you see the display?
Yes, you can. And then we have the list of the values here, which you will be given. The customer on this occasion has chosen to go with the Audio Note, half watt, non-mag, tantalum resistors, which are all here. So with the probes on my DC resistance, I'll put them in the vice just to hold them in place like that. Okay. And then I will just go through every single one. I know it's a bit laborious, but you do not want to make mistakes. So this one, which I know to be 10R. So pick it up like that. There you go. Take that off. I'll just test both of them. So I'm hoping that display says 10R, which I think it does. And then the next one, 10R, which it does. Sweet.
So I will go through the whole thing and just make sure all of those resistors are the correct value. I have done this earlier. So now I'm going to populate the board. So as I said, the resistors coming this way for the half watt. So that's where the actual switch mech is there. I'm going to check it on here. Obviously I'm dealing with the low values first. You can see that there's an R IN. So that is the load resistor. This particular customer doesn't want me to put anything in that position. He's probably got a setup where he's doing it himself, somewhere down the line. So I will send those separately. He's probably putting them in a location that isn't on the board. So ignoring the R IN, I'm going to start at R2.
And then what I generally do is I have a like an Allen key like this, so everything's uniform. And then the lead that has the tolerance band there. I will basically put that down tolerance band near the board. So then on this I'll just roll it over like that. Pull it out. So you've got a nice regular curve on there. And then I will just populate the board like that. So you can see that's how it works. So the circle is where the resistor sits like that. And then I'll go all the way along. Now you can see you think it's going to go in sequence, but it doesn't. On a couple of ones it doesn't go in sequence. So like on the third line you've got R9 but then directly below is the R10.
But you wouldn't think it would be there. You'd think that'd be the R12 because it would go but it doesn't. So just be very, very, very, very cautious and check what your work is. So I as a rule will populate all of that and then I'll show you the next bit. So I have populated one side of the board like this. You see all the danglers. I'm not checking the resistances because I've already checked earlier. So to solder them we have to turn the board around. Obviously all the resistors are going to fall out. So I just use some black electrical tape. You need a couple of lengths of it. About that length. That length. And then, just like that, stick it down to the board, side of the board, and do that to the other side. Cool.
Keep your hands on it like that. You see? Keep your hands on like that. Turn it around and grip the bits of tape like that. Now you're going to have to pull the tape back so you don't want to melt that. Make sure all the resistors are still... You don't want them popping out because it will impede the positioning when you fit it. So I'm just going to solder all those. This particular customer is loving the Audio Note so I'm going to use the Audio Note solder which I can't find. Anyway next time you see me in a second these will be soldered and trimmed and then I'll do the same to the other side. And then I will show you about putting this switch back together with all the gubbins.
But Johnny hopefully will be back by then next week and you'll get more of a detailed view. So I'm just going to be building a switch so it looks like this. So I've done one already. Here's all the bits and bobs. We always put these things together. So, [unclear] the base. Make sure it says one, two, three, four. So that's towards your body like this. Pop it in. Center. Oops. So to get it in, you have to give it a push like that. So that's in. The cover goes like this. So that stops any dust getting in. So you can see that hole's blind blank. There. So that's the one that goes nearest to you. Big black washer. Like that. Over the top. So the spring. This is where the contact is and the contact are like that.
So contact's in there. Pop it in the hole. Pair of pliers. So this applies force to this. Drop that in. Right. So, oops, I just nudged it in there like that. Cool. So that's bouncing up and down on there. Cool. Um, now this is the thing going next, but you have to prep the screws. Screws go into the washer. Like so. These washers go on the inside. Around. A bit of pressure there. So this raises up the board on the switch to the correct height. Great. Just need a screwdriver. So you're turning it around like this. This bit goes to the left side. But before you do that, you have to put this washer at the top like that. Fits in there nicely. So come in from the top. Push down. Line up the holes.
Two really thin washers like this. Two. And then to put this circlip on, I need to [unclear] raise it up. Cool. So that's in. So that's working. So I have a list of all the values. So I'm just going to do a test. So one goes on ground, one goes on out. You get zero and then you start winding up. And you just cross reference all the values. Which I can see. Always does that at that stage. I don't know about that. It's just the meter. All the way up. That's all good. One more, and an open circuit. Brilliant. All done. So that can be shipped. Boom. 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.
Thank you.