I can paint during blackouts, I can play with handheld sequencers during blackouts.

Basically, I got bored and started making theme songs for tacky game shows of the 1970s which never existed. None of these were good, of course, but this one was probably the least bad – I figure it’s circa 1977, a slot-machine celebrity-trivia-themed game show involving a lot of guest appearances by Jo Anne Worley and Phyllis Diller.

Oooh, bad luck there. <sad horn> Next contestant, pull that bandit!

Oh right, painting. Yeah, this is probably the last speaker post. I finally connected them up to my Samson amp to test the old-style connectivity, and the little Class T amps I added in are definitely better. Okay, the Samson has more bass, that’s fair. But wow, these miniboard amps are a lot more precise and focused in every other way.

And after the power went, out I painted ’em. These pictures aren’t 100% before-and-after, because I’d already cleaned them up a lot before taking the “before” shots. Yeah. Literal caked dirt filling the foam rings around the woofers. Sound quality aside, just consider that for a minute.

Yeah! This is what I meant on Twitter about looking like they belonged on a stage. Go you, paint!
 

This post is part of a series on restoring infamous vintage stage monitors. Spoiler: they made good, in the end.

John Seghers, local sound guy, gave me a set of locally-infamous and astoundingly terrible stage monitors. I mean, seriously, they just hurt to listen to; musicians would cringe when they saw them on stage.

They’d been through a lot of bands by the time they reached me, and came with an amp I was also being given. They were, in fact, more or less the price of the amp – if I wanted that, I had to take these wretched things too, just so John didn’t have to haul them to the dump.

And upon testing, they were indeed hilariously terrible. They totally lived down to their reputation. There was dirt caked in the speaker foam, and they were filled with fibreglass insulation and in one case quite literally a small dead animal. I was looking at a parody of bad stage gear.

But that is not the story. The actual story is how it turned out they were secretly – very secretly – great, just… buried, and muddled beyond all recognition.

They’re back now; for the first time in literally decades, they sound really, genuinely good. But it was a long way home. This is how we got there.

• None of This Was Expected: Finding out that inside these infamously-terrible stage monitors are unquestionably great elements (25 March 2015)
• Absolutely Flat Equalisation: On building new crossover circuits (27 May 2015)
• Wherein I discover that “Class T” amplifiers are a thing, and cost all of US$20 or so (20 July 2015)
• Give This Board a Proper Power Supply – building a proper test harness for a Class T amplifier and discovering it’s full of LOUD (9 February 2016)
• This New Panel Is Looking Like Old Star Trek: if I’m going to upgrade this to self-power and modern specs, I’ll need a new interface panel
• More and More Like Star Trek: Wherein I work with Delrin, a long-polymer machinable plastic (22 February 2016)
• A Few Quick Pictures of the finished panel (23 February 2016)
• It is IMPERFECT but it is WORKING so I am CONFLICTED: Up and running! But I had to swap out a piece and it’s a bit off axis. Gir! (24 February 2016)
• Science-Related Memetic Disorder? Wherein I realise I could make this thing Bluetooth. (24 February 2016)
• I have basically implemented a Polish joke about the Soviet technology, only for real. (10 March 2016)
• I Can Still Paint During Blackouts, wherein I spruce up the cabinets because electronically, this project is finished! (14 March 2016)

The original back panel – anybody ever heard of this crew?

Yesterday it was Polish jokes about Soviet technology; today it’s trying a Russian-made TUNG-SOL tube in that ART TUBE MP mic preamp I played with last week. I got advice from Ben Deschamps that I should, because the ART preamp ships with whatever was cheapest that day, and swapping tubes around can make a big difference.

And, hey, I think in this case it rather does. I’d apparently had a best-case low-bidder tube before, so bringing in the Russian didn’t make a big difference in noise level. But the amp’s tonal differences are certainly highlighted.

I should note: I also realised I could bypass the mic preamp stage in my TASCAM completely by going to line-level inputs, as opposed to leaving it in the mic input port at zero gain, like last time. The effect should be similar, but may not be. Regardless of which change mattered the more, I really think you can tell a difference between the preamps now, even in mp3.

The Russian-made tube gives the ART TUBE MP a lot more of what I think of as a “guitar amp” sound. That’s 100% unsurprising, now that I’m typing it out, but it’s still interesting to hear it.

The way that this preamp “likes” mid-bass is emphasised more, I think, as is its noted disinterest in the finer points of higher harmonics. That part of the sound reminds me of the AKG microphones I have, but with more interesting sonic effects down in lower frequencies. I suspect it would get on well with cello, as the AKG200s do.

I don’t know that I’d call the ART “warmer” at the high end – I might call it “less precise” – but it’s certainly a difference regardless. I should try this with the AKGs, later, to see if their similar areas of interest lever each other up a notch, or clash in some unfortunate way. Pleasantly, I have pairs of those, too.

For the recordings linked below, I’m switching between the two basically identical M-Audio NOVA large-can condenser microphones set up side by side and played into simultaneously. The levels are as close as I could reasonably get; it was a bit harder this time, as there were audible differences, and I’m using a bit of light compression as would be used in real life.

Unlike before, since the difference between the two preamps is more obvious, I’m also including a 50/50 mix between the two inputs during one of the repeats in each of these. That produced some interesting qualities, I think, on the octave mandolin.

In both recordings, ART MP tube pre-amp starts; TASCAM follows. Tell me what you hear on your speakers!

• Irish Bouzouki (mp3) – “Supervillain For I Love You (intro only)”
• Octave Mandolin (mp3) – “Thirteen” (a few chosen chordal excerpts)

Whaddya think, sirs?

I have basically implemented a very old joke from Poland about Soviet technology:

A Pole waiting at a railroad platform in Moscow wants to know the time. He sees a man approaching him carrying two large, heavy suitcases, and asks the fellow if he what time it is.

“Certainly,” says the Russian, setting down the two bags and looking at his wrist. “It is 11:43 and 17 seconds. The date is Feb. 13, the moon is nearing its full phase and the atmospheric pressure stands at 992 hectopascals and is rising.”

The Polish visitor is astounded, and asks if the watch that provides all this information is Japanese. “Not at all,” says the man, indignantly. “It is a product of the latest in Soviet technology!”

“Well!” says the Pole, impressed. “That is wonderful, you are to be congratulated!”

“Thank you,” the Russian answers, straining to pick up the suitcases as the train arrives. “But I’ll admit, these batteries are still a little heavy.”

To wit, these self-powered iPod speakers:

iPhone compatible

Okay, they are obviously not actually generally for use as iPod speakers. They’re the stage monitors I’ve been working on occasionally for the last few months, but they are now both rebuilt to be self-powered! They have 50-watt Class T amplifiers built-in, as well as power converters for line voltage. I knew all those spare computer power cables would come in handy eventually.

I did not, despite temptation, add Bluetooth. But I could.

Now it’s time for some burn-in. Hopefully, I’m almost done! 😀

eta: Well, hell, the new amp’s channel 1 got noisy after a couple of hours and stayed that way. channel 2 is clean so far – all of these boards are dual-channel – let’s hope it’s good.

eta2: So far, so good: WE’RE BURNINATING THE AMPLIFY (video with sound)

eta3: With this speaker, they apparently originally tried to put the panel right behind the tweeter horn, where nothing could be inserted. Then they moved it and patched the hole with plywood. I just made it one big panel, with a big blank area.

This post is part of a series on restoring infamous vintage stage monitors. Spoiler: they made good, in the end.

Leannan Sidhe and I were kicking around at an estate sale – she was looking at some PA kit that had been advertised, turned out really not interesting – and I noticed a little neglected microphone pre-amp sitting in the corner. I’ve never bothered with separate microphone pre-amps, much less tube-driven ones, but I was curious about it.

So I went to the manager running the show, and said, “I don’t need this, but it might be fun to play with, what’s your best price?” And so I strolled off with it, and today I set up a pair of side-by-side M-Audio NOVA large-cap condenser microphones to make some simultaneous recordings. Both mics ended up going through my TASCAM interface, with one going through the tube preamp first, then to the TASCAM with the TASCAM’s gain cranked down to zero. The control mic gain on the TASCAM was set to match final recorded levels. A few samples are linked below.

First thing I noticed: jfc this thing has gain. If I need something LOUDed at the pickup level, I now have that piece of kit. I kind of had that kit already, but that was the ribbon-mic preamp I built specifically for the ribbon mic I built, and that can’t provide phantom power like this does. (And it shouldn’t; phantom power destroys some ribbon mics, including mine.)

The second thing I noticed is that… the difference is pretty subtle. I mean, I expected that. And part of that might’ve been having both lines going through the TASCAM at the end – but it had to go through something for digital conversion, or I can’t record.

In studio, I can hear small but audible differences. The TASCAM’s preamp seems to like mid-bass more than the ART TUBE MP. I think there’s a little quicker response in low base in the ART, in a way that I recall from tube amplification equipment like EICO and Dynaco gear.

Outside the studio, though – on a good consumer headset on my laptop? I’m not hearing much of any difference in 320kbps mp3. I think I’m hearing a little in uncompressed WAV files, but not a lot. That may be the laptop’s D/A converter, I don’t know. On the laptop speakers, I don’t hear anything different – though really that has to be expected.

Worth it? For what I paid, sure! I have a serious business gain DI/pre-amp out of it. Sound-wise? I dunno. I really do think there is some subtle difference and if I’m in an environment where I’m having to rein in mid-bass and pop the low end a bit, maybe it’d be better to do it with this thing than in equalisation later. Probably would be, in fact. But it has a pleasant enough sound to it, regardless. I’ll probably play with it on bass guitar, later.

Anwyay, here are some recordings – they’re edited so that consecutive repeated musical phrases alternate between the ART tube amp and the TASCAM interface’s built-in mic preamp. What do you think – do you hear anything?

Irish bouzouki: WAV mp3
Octave mandolin, tuned to open E5: WAV mp3
Bodhran, two different strikers (traditional, bamboo): WAV mp3

eta: I make a point of not talking American politics here much, but I do elsewhere, and watching the GOP’s civil war start in earnest is kind of neat.

I realised this morning that I could totally add Bluetooth to this monster of a stage monitor I’ve been rebuilding and upgrading. I’ve made it self-powered and compliant to modern specs, why stop there? It’s portable! It even has a handle!

48 pounds! Two pounds less than a standard bag of concrete! PORTABLE!

I mean, okay, sure, I’d need a second one to deliver full stereo, but I could do that because I have two of them and could put on another jack to share channel two over to the second speaker and and and IT COULD WORK!

Someone please put a towel over my head.
 

This post is part of a series on restoring infamous vintage stage monitors. Spoiler: they made good, in the end.

So yesterday I mentioned that the first stage monitor had some physical issues, and what the big one turned out to be is that one of the XLR sockets on the new control panel extended too far into the cabinet, and rattled against the tweeter driver.

That’s really annoying and generally not good, but fortunately I have some shallower ones handy, and hey, the hole is about the same size, and hey, the screw mounts are about the same distance apart, this should be perfect!

Not as much.

Now, this has exactly zero functionality impact. It really doesn’t. But wow, it’s annoying. Not quite annoying enough to make an entirely new Delrin panel and unsolder and reconnect every wire, but still. Annoying.

Anyway, it’s totally working now. I have successfully upgraded this antique to modern specs. It’s not quite like taking an old grandfather clock and setting it up to run network time protocol, but… actually it’s a lot like that. Go Team Pointless! Except it’s not, it’s actually useful now.

The link is to video made on a phone of an iPod playing through the speaker by direct cable connection, no other parts. Yes, it’s also now the heaviest portable – luggable – iPod external speaker ever.

Tho’ even with the wonky socket, the panel still looks decent labelled.

Made and Designed in Cascadia with Chinese, Canadian, American, and Cascadian Parts.

I’ll open it back up to tie down some cables, but other than a little more testing, this one’s done. Speaker two is next. Probably won’t post many photos, it’d just be reruns. But if I learn something I’ll post about that.
 

This post is part of a series on restoring infamous vintage stage monitors. Spoiler: they made good, in the end.

As per Twitter last night, installed, it’s looking a little less like Star Trek and a little more like K-9. So I’m calling it dB-90.

There are a few more physical issues to work out (something rattles when loud), but it’s getting there. Here’s a video not loud, recorded after everybody else was asleep.

This post is part of a series on restoring infamous vintage stage monitors. Spoiler: they made good, in the end.

So following up on materials suggestions made in response to the previous post on this stage monitor project, I’ve been playing with Delrin (acetal copolymer), a long-polymer-chain plastic.

It looks even more old-Star-Trek than the diagrammes I made. Seriously, I’m wondering if they made the bridge consoles out of this stuff. Cut a bunch of holes for buttons into it and you’re off.

Which is exactly what we’re about to do. But first, lj:tereshkova2001 asked if I would report back about how this plastic works as a material. Since that’s pretty hard-core geekery, I’m including that down at the bottom of this post, and talking about the panel assembly first.

So after I cut off my new panel backing from the rest of the sheet I’d bought, I decided the easiest and best way to place all these holes would be to adhere the printed scale diagramme to the plastic itself, and just drill through the paper at appropriate points.

Since movable spray fixative doesn’t seem to be a thing anymore, I came up with an alternative plan of two layers of tape – one single-sided, one double-sided. The single-sided layer is packing tape (of which I have lots), applied to the panel:

One of the reasons I didn’t just use double-sided tape in a single layer is that stuff is really hard to remove, so if I tape it to tape that’s easier to remove, I don’t have to fight that battle. Also, the packing tape is wider, meaning the holes cut in the tape don’t break any single entire length of tape, which means I always have a section of “handle” when pulling the tape up once we’re done.

Anyway, then the double-sided tape goes on the back of the cutting diagramme:

And that gets us to the third reason for two layers of tape: I had to position the diagramme on the panel so the hole guides are in the right place. You can’t really draw on Delrin, or on double-sided tape, but you can certainly use your pink glitter gel pen on ordinary packing tape just fine:

And now you know exactly where to position your cutting guide/diagramme on the panel.

BREEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

As I was warned, this material really likes climbing the drill bit. That’s true for any plastic, and this isn’t worse, but it isn’t better, either. Fortunately, that wasn’t doing any actual damage. This is what one of the holes looked like:

Along with an insert test, which showed that yep, this seems to be working fine. I drilled out the rest of the holes, and peeled off all the tape. Having tried this before with double-sided tape only, adding the packing tape layer made this much easier.

Eventually I got most of the sockets and switches and such in place. A few of them needed separate bolts to hold them onto the board. Drilling those holes also involved tape for position control, but in a slightly different way. Again, you can just drill through the tape:

As of writing this, I have all the components integrated into the panel. I’m really pretty happy with it. There are a couple of little scratches which aren’t my favourite things in the world, but it’s not like anybody will notice them, ever.

As you can see, I have started wiring the thing. Green light means “plugged in,” red light means “power switch is ON.” Those are neon and I’m a little worried about noise from that – it’s not supposed to be an issue, but No Trust I, so I’m probably going to wrap the backs of those in copper shielding. If I have to, I can cut them out entirely and have no harm done.

And besides, it looks pretty cool.

I still need to drill attachment screw holes around the outer edge of the panel – which I kind of forgot about until just now, oops – but that won’t break anything. Then it’s wiring harness time!

I hope this keeps working out. See, what I’d really like to do is be able to move up to a modern iPad-driven sound system, but all of those use and expect self-powered speakers. If I can make these passive monitors into self-powered and it actually works? That’d let me actually move my gear into this century. Which would be really nice.

Anyway, that’s where the project stands right now. Hopefully I’ll get to work on it more tonight and have another update soon.

Now, as promised – NOTES ON HANDLING AND WORKING WITH DELRIN!

For the record, I’m using the basic Delrin formulation (no glass particles added as a hardener, etc), at 3/16^th” thickness.

absynthe77’s comment that it works kind of like a very soft aluminium kind of stands up. It’s not exactly like that – you can melt this with a cutting wheel in ways you can’t melt aluminium, for example – but I see what they mean.

The aforementioned melting is minimal and not bothersome. It doesn’t clump up into a paste like acrylic plastics do, which is much nicer, and it doesn’t foul your tools, which is critical. You can cut it with an edge-grinding Dremel bit and it doesn’t get goopy and weird; it flakes off in manageable pieces, instead. But it’s still soft enough to cut with a basic Dremel cutting wheel and I haven’t accumulated much wear yet.

Here’s an edge cut made that way:

Note the circular-saw-like cut pattern; it didn’t melt the plastic away, it cut.

Unlike acrylic, Delrin does not score-and-snap. I gave it quite the depth of cut and got absolutely nowhere trying it. I even gave it another go after getting out a cutting wheel, just to see if I hadn’t scored enough, but no, it just wasn’t having any of it – not until I was almost entirely through the sheet. So while it has some flex, it’s very strong against snapping and cracking.

In some ways, working with it kind of reminds me of linoleum block print cutting, only a much harder material. With a Dremel cutting ball, for example, you can scoop bits of it out, almost exactly like linoleum block cutting. That’s pretty nice, and is how I made the square holes I needed – well, that and an xacto knife and file for finish work. Most of it was just scooping out plastic with the Dremel.

I haven’t worked with many plastics, and when I have, I generally haven’t enjoyed it, but this… this is fine. Fouling isn’t an issue, it doesn’t send sparks like metal so you don’t have to worry about shop-vac fires and can run the vacuum the entire time, I didn’t really seem to be able to overheat it in a meaningful way.

If there’s a downside, it’s that it does scratch like plastic, and more easily than aluminium. So you’ll need to take some care with that. It’s not look-at-it-funny-and-it-scratches soft, but a stray screwdriver would definitely leave a mark.

So, yeah. Definitely something I’m glad to be able to add to the toolkit. At least, so far.

eta: I’ve discovered the old speaker-level inputs used by both speaker and amp are an obsolete cable connection standard. I’m upgrading the speakers to self-powered, but I want to maintain the speaker-level-input functionality too. Do I re-implement the old standard? I mean I guess so, but. Ugh.

eta2: It was, for the record, a stupid standard.
 

This post is part of a series on restoring infamous vintage stage monitors. Spoiler: they made good, in the end.

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.
 

This post is part of a series on restoring infamous vintage stage monitors. Spoiler: they made good, in the end.