this new panel is looking kind of old-school star trek

[solarbird]

Now that I’ve had good test results from the Class-T amp I’m using to make those old stage monitors into self-powered stage monitors, it’s time to whip up a new plug panel for the new connectors needed – power, line-level input, and so on. This process is raising more questions than I expected, so this post is partly me thinking out loud, and partly taking suggestions.

When I got these speakers, they had unbalanced XLR in, and unbalanced XLR daisy-chain, and that’s all. That’s kind of weird these days, so I added a 1/4″ unbalanced (“phono”) connector. That looked like this:

But unbalanced 1/4″ phono plug is not really optimal for powered speakers, because the signal going to the speakers is line level, which is a lot lower, and therefore a lot more subject to interference. So I need some sort of balanced input, I think. Also, I still want to be able to use the speakers in their original intended mode – as passive devices driven by external amps, so I kind of need two connectors. Plus the soon-to-be-built-in amplifier needs a power lead, and it’d be nice to have a couple of status indicators, and so on and so forth.

So that all fits together in the existing amount of space like this:

Without and with labels

So does the drill pattern for all the holes I need in this new panel. I had been thinking of adding a second panel or something, but since I was able to make it fit, I think I’m better off not bodging more exceptions into the cases.

My initial thought was 1/4″ plywood – I have that, it’s easy to work with. But now I’m looking at the number of connectors which are involved here, and the number of resulting holes, and I’m thinking, should this be metal? Or would a particularly sturdy plastic work?

The original was metal, and I’m pretty sure I mean steel. It’s sure as hell not aluminium – adding one jack to it was a huge pain in the ass, and aluminium isn’t that hard to drill out.

So, yeah. Plastic would be a lot easier, but would it be sturdy enough? Serious question, I don’t know. Aluminium would be easier to drill and file than steel, and is still pretty strong. But that’s still a lot of work.

Maybe I could/should get someone with a cutting system to cut it out for me. I know that’s a thing you can hire out, but I don’t know anything about it. I have a scale drawing and that’s all.

I guess I can ask Fishy that when he gets back from Tokyo. But I hate waiting once I have all the parts for something. Anybody got experience with hiring out metal cutting in Seattle, and know things like how much that cost? ‘Cause I have no idea.

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Comments

[vatine]

If I had unlimited time on expensive machines, I'd probably use 1.5 mm mild steel and have the holes cut on a water jet (laser cutters are shinier, but my understanding is that metal gasses are No Good At All and water jets are probably faster). Not sure what there is nearby in terms of service bureaus able to do that, but that may well be a good solution.

I've also seen faux-pillar-drills that take a handheld (corded or cordless) to save you a small bit of elbow grease. No idea about prices (I doubt tool prices are commensurate between UK and US in the general case), so that might also be an idea. I'd probably use a small-ish drill to center-drill all the round holes, not sure what to do about the square ones. Probably "drill close to corner, saw, file the corners out".

[solarbird]

I know Fishy has had people water-cut things for him, so I'll definitely ask him about that once he's back. It does strike me as a lot easier. I just don't know about time and how to get them data and and and.

If I end up doing it myself, yes, it'll be drills and hand-saws, which is why aluminium or some good plastic is going to be important if I go that way. But I'm nervous about that for strength reasons.

I actually have one of those fake pillar drills (drill press, here) - goes with a dremel tool, though, not a full-size drill. But I'm already all right without that, I think. I use me as a pillar, and have the metal atop scrap lumber. ^_^

[vatine]

I think "pillar drill" is actually Swedish shining through. I think (but may be wrong) they're drill presses in the UK as well. I've seen both the hand-held-drill and Dremel variants, but a hand-held usually has a bit more oomph than a Dremel. Main reason I was thinking about them is that they (in my experience, at least) tend to both allow you to use less force as well as tending to improve the precision. Although the non-dedicated units are somewhat wobbly, but should still allow you to get ~1 mm accuracy.

Plastic, pretty much any plastic (except possibly fibre-glass reinforced ABS), I would worry about stress cracks. And you REALLY don't want the reinforced ABS, as it eats about one tool-steel drill every, oh, 100 mm of material drilled through (yep, spent a summer machining the stuff, it's lovely but really hard on tools).

If I decide to make another arcade controller for home (I think the old one is dead by now), I'll probably buy one of the "takes a hand-held" drill press jobbies. It worked fine doing it by hand, but that's enough holes and boring (ahaha) enough that I'd rather spare my back from the hunching. On the other hand, that's somewhere in the region of 25 holes. On the gripping hand, it was in wood (Ivar shelving, so it hooked on nicely just above my Ivar computer shelf thing).

[solarbird]

Stress cracks are definitely on my worry list. Delrin (acetal copolymer) was suggested over on Livejournal - the write-ups on it seem promising and I like the nonconductive material since I'm sending both line level and AC mains power through it.

[vatine]

Delrin is certainly pushed as "machinable plastic" and may be worth a try. I've certainly heard of people use it as stock when practicing lathe techniques.

[solarbird]

I think I'll give it a go. I haven't worked with plastic much at all (almost never, really) so it'll be a new experience, and that's instructional.

Also, absynthe77 on LJ specifically thinks the stress fracture properties are very good due to it being such a long-chain polymer.

If that doesn't work, I'll probably go to aluminium.

[solarbird]

Oh, the other thing, regarding the machineability - absynthe77 says it lacks the heat buildup problems of acrylic plastics, which are the only other plastics I've worked with ever. So that's very good.