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The Starving Student Millett Hybrid PCB
Construction - Wiring & Assembly
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Coming down the home stretch!! We've finished it all except for the endplates. What's really nice - there's no work at all on the front plates (with the custom Beezar/Hammond case). Once you slide the assembly into the case, that's it - the endplate is already drilled to match the volume pot shaft and the headphone jack. The back plate is not as simple, but still not too bad. I get discouraged at this part, though, because to me, wiring is so tedious. What's nice and makes up for that, though, is that you don't have to drill the holes through the back plate and worry about dimensions, hole sizes, or whether it will all fit - it's already done (with the custom Beezar/Hammond case)! |
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So, given that, the only thing we have to worry about is the connectors on the back plate. These are the Power Input Jack, the Power Switch, and the RCA Input Jacks. These are pictured here in a blowup of our kit parts layout shown way back on the construction overview page. |
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22. Install the Power Switch - The power switch, while rated for much higher voltage, is plastic. Thus, it will melt enough that the mechanism may be damaged if you use a soldering iron to connect wire leads to the tabs. Instead, use a couple of fast-on connectors as shown here. These are available in every hardware store. In fact, the ones shown here are for much larger tabs, but they work fine for the power switch, regardless. Be sure you crimp them so that the wire is snug. Pull on it and work it back and forth to make sure you have a good connection. I have to crimp it in two places, but maybe that's because I use the cheap tool shown in the photo. |
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Before we install the power switch, we'll want to prepare the back plate for the connectors. As with the case lid center hole, we want to scrape the anodizing away from the holes so that the connectors' negative connections will make contact with the case. Negative = Ground in the SSMH, so again, our ground resource will be increased when we do this. Just an FYI, but the RCA jacks fit snuggly enough that the edges of the drilled hole may be sufficient to provide contact. Still, if you're scraping/filing anyway - might as well do them all (except for the power switch - that's all plastic, so it won't do any good). |
| Note - be sure you know which side is which! The outside of the endplates have counter-sunk mounting screw holes. That's the absolute indicator - do your filing/scraping on the other side. The counter-sunk part of the holes are the outside. |
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23. Install the Power Input Jack, the RCA Jacks - Similarly, install the power input jack and the RCA jacks. Both require soldered connections, both ground and non-ground (or signal). The pic shows my usual workspace once I start wiring connectors - all h*ll breaks loose and the whole table turns into a mess. In the photo, we can see the power input jack already wired and screwed into the back plate (more on that later). The power switch has already been installed on the back plate, and I'm in the process of finishing the wiring connections on the RCA jacks. |
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Here's a glamour shot of my soldering one of the ground leads on the RCA jacks. Some use a single ground wire and solder it to both tabs of both RCA jacks. However, I think two ground wires - one soldered to each tab separately works better. |
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The backplate finished with all connectors installed and the wire leads soldered. Note that when measuring the length of the wire leads, insure that you have enough slack to move the back plate up and over the main case body - this is the way that dis-assembly will be done. Also, note that the signal wires from the RCA jacks must be much longer to reach the input signal terminal block. |
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An outside view. Note the insulators on the RCA jacks. Actually, the RCA jacks are best without insulators. As shown in the photo previous, there are no insulators on the inside - this is so the RCA jack grounds can make contact with the case. On the outside, the insulators are purely cosmetic. You'll find that it's almost impossible to plier the jacks down from the outside without scratching a circle into the backplate finish - the insulators will protect the finish and allow easier tightening. |
| With the power input jack, the hole is purposely sized larger than needed. This is because Radio Shack makes a similar power input jack that's larger in diameter. I left the hole big enough in case some want to use that jack. The jack in the kits will benefit from an additional finishing washer - simply use one of the washer/spacers that come with the headphone jack - not all of them are needed for the headphone jack. |
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24. Install Wiring and Back Plate - Trim the wire leads to length if needed, but remember, there's a huge space behind the PCB - plenty of room to take up slack. The back plate must be able to move up and over the main case extrusion for convenient disassembly, so quite a bit of slack is needed. Note also that the input signal terminal block is quite close to the case sides when assembled, so bend the wire leads at a 90 degree angle next to the terminal block and trim to fit. This makes it easy to obtain enough clearance for the input wiring. I like to braid mine in a Litz braid or similar, but I'm not sure it means anything over this distance. |
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25. Assemble the Amplifier - Hey! We're done! Be sure to use the endplate bezels. Don't worry - you can slide the bezel over an endplate even when the wiring is connected. For the front plate, use one spacer on the headphone jack behind the endplate - that should be sufficient for spacing. |
| Pictured here, I've assembled it without the screws. If everything works, I'll disassemble it, tap the case holes and use 6-32 machine screws. That's not really necessary, though, the supplied Hammond screws will work fine - but don't use them until you're certain the case and the amp all work fine. |
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Back view. |
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And we add the volume knob - the idea is to get it as close to the endplate without scraping anywhere in its travel. This may be sometimes more difficult than it sounds - it depends on how well you aligned the volume pot when you soldered it way back when. |
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Finished!! All fired up and glowing - I used ocean-green LED's for this one. |
| Give your Starving Student time to burn in. I'm not an advocate of hundreds of hours like some claim for headphones, etc., but your Starving Student will definitely change tone in the first hour or two. When you first power it up, it will sound bassy, thick and "cloudy." Within an hour or two, the tone will have changed 100% - more detail, more transparency. Things will continue to improve over the next 12 hours, with subtle changes after that as more detail and transparency comes in. The electrolytics and Wima caps take time to burn in - not hundreds of hours, but definitely over a day or two - that's a fact! |
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