Spoofing An Analog Rotary Knob With An ATtiny, And Vampiric Power

[Mitxela]’s repair of a Roland JV-1080 (a rack-mounted 90s-era synthesizer) sounds simple: replace a broken rotary encoder on the front panel. It turned out to be anything but simple, since the part in question is not today’s idea of a standard rotary encoder at all. The JV-1080 uses some kind of rotary pulse switch, which has three outputs (one for each direction, and one for pushing the knob in like a button.) Turn the knob in one direction, and one of the output wires is briefly shorted to ground with every detent. Turn it the other way, and the same happens on the other output wire. This is the part that needed a replacement.

The finished unit uses a modern rotary encoder and microcontroller in place of the original part, and implements a few tricks to power it.

Rather than track down a source for the broken part, [Mitxela] opted to replace it with a modern rotary encoder combined with an ATtiny85 microcontroller to make it act like something the JV-1080 understands and expects. There was an additional wrinkle, however. The original rotary pulse switch is an entirely passive device, and lives at the end of a four-conductor cable with no power provided on it. How could the ATtiny85 be powered without resorting to running a wire to a DC voltage supply somewhere? Success was had, but it did take some finessing.

For the power, it turns out that the signal wires are weakly pulled up to +5 V and [Mitxela] used that for a power supply to the microcontroller. Still, by itself that wasn’t enough, because the ATtiny85 can easily consume more current than the weak pullups can source. We really recommend reading all the details in [Mitxela]’s writeup, but the short version is that the ATtiny85 does two things.

First, it minimizes its power usage by spending most of its time in sleep mode (consuming barely any power at all) and uses an interrupt to wake up just long enough to handle knob activity. Second, the trickle of power from the weak pullups doesn’t feed the ATtiny directly. It charges a 100 uF capacitor through a diode, and that is what keeps the microcontroller from browning out during its brief spurts of activity. Even better, after browsing the datasheet for the ATtiny, [Mitxela] saw it was possible to use the built-in ESD protection diodes for this purpose instead of adding a separate component.

It’s a neat trick and makes for a very compact package. Visit the project’s GitHub repository to dive into the nitty gritty. In the end, a single assembly at the end of a 4-wire connector acts just like the original passive component, no extra wires or hardware modifications needed.

When opening older hardware it’s never quite certain what will be found on the inside. But at least [Mitxela]’s repair duties on this synth didn’t end up with him tripping out on LSD.

Hackaday Links: February 10, 2019

Last month was NAMM, the National Association of Musical Something that begins with ‘M’, which means we’re synthed and guitarded out for the year. The synth news? Behringer are making cheap reproductions and clones of vintage gear. There’s something you need to know about vintage gear: more than half of everything produced today has a Roland 808 or 909 drum machine (or sample), a 303 bass synth, or a 101 mono synth in it. Put an 808, 909, 303, and 101 on the same table, connected to a mixer, and you can make most of the electronic music from the ’80s and ’90s. And Behringer is cloning these synths. Neat times. But there’s a problem: Roland is trademarking these drum machines and synths, with trademark filings in the US and Germany. These are ‘trade dress’, or basically the beautiful red, orange, yellow, and white buttons of the 808 and the digital cyber silver plastic aesthetic of the 303, but there you go. It’s round one in the Roland v. Behringer match, may the first person to give me an 808, 909, 303, and 101 for a thousand dollars win.

Synths? Sure thing. Here’s a stash of New Old Stock 8580 SID chips, the ‘synth on a chip’ found in the Commodore 64. The price? $50. [ben] bought one of these, and the card that came with it said,  “We purchased these chips in 2006 and they’ve been stored in our climate-controlled storage area ever since. Even still, we found a handful of them that didn’t pass testing. Treat them with care!” Yes, a bunch of SID chips for sale is noteworthy, but at $50 a piece for 1980s technology, can someone explain why a chip fab isn’t cranking these things out? If there’s one ancient piece of silicon where the demand meets what it would cost to spin up the silicon line, the SID is it. Where are the modern reproductions?

Excited about making an electronic badge this year? Seeed is offering badge sponsorships for 2019, with an offer of a 5% discount on PCBA, and a 10% discount if you put the Seeed logo on the board. I might be a little biased, but Seeed is a place where you can just ask, “hey, you guys do clear soldermask?” and they find a way to do it.

The best way to tell if someone is rich isn’t by seeing if they have an i8 parked outside their mansion, or just a piece of junk with an M badge. It isn’t whether or not their filet mignon is wagyu or just Kobe, and it isn’t if they’re cruising the skies in a G650 or just puttering around in a Cessna Citation. No, the best way to tell if someone is rich is to notice their AirPods. Yes, Apple’s wireless headphones (which are actually pretty good!) are the best foundation of a class division these days. The best class signal since private railroad cars now has a problem: people are printing their own AirPods. [Brady32] over on Thingiverse has modeled AirPods, and now the design is being given away for free. The horror. Now anyone can print out their own little bits of white plastic, stick them in their ears, and tell the world, ‘I’m better than you. Don’t bother talking back, because I obviously can’t hear you.’

Raspberry Pi has a store! Yes, everyone’s favorite single board computer now has an ‘experimental space’ in Cambridge’s Grand Arcade. The Beeb is saying this store is ‘bucking the retail trend’, yes, but any retail trend doesn’t really apply here; brands have storefronts, and it’s not about revenue per square foot. Makerbot had a store, and it wasn’t about selling printers. Microsoft has stores. Sony built a mall to advertise the original PlayStation. While the Raspberry Pi brick and mortar store will probably never make any money, it is an indication the Raspberry Pi foundation has built a valuable brand worthy of celebration. Here’s some pics of the store itself.

Did you know Hackaday has a retro edition? It’s true! retro.hackaday.com is a lo-fi version of Hackaday without CSS or Javascript or any other cruft. It’s hand-written HTML (assembled by a script) of the first ten thousand or so Hackaday posts. The idea is that old computers could load the retro site, just to prove they could. [Matthias Koch] has an Atari PC3 — Atari’s PC compatible with an 8088 running at 8Mhz, 640k of RAM and a 20 MB hard drive — and got this thing to pull up the retro site. Good work!

What is the current state of 3D printing? What is the current state of 3D printing videos on YouTube? Oh boy we’re going to find out. [Potent Printables] did an ‘analysis’ of 3D printing videos published to YouTube, and found the category riddled with ‘clickbait’, without giving an operational definition of what ‘clickbait’ actually is, or how it’s different from any other content (because who would make a video that doesn’t have the purpose of attracting viewers) Anyway, there’s a problem with the YouTube algorithm, and 3D printing blogs are copying it, filling the entire hobby with disillusioned beginners, or something. After defining ‘The Most Viewed’ as not being a news or documentary footage (okay, that’s fair), having at least three printing videos, not clickbait, and gives the designer proper attribution, [Potent Printables] found a list filled with [Maker’s Muse], [3D Print Guy] and other channels who do 3D printing work, but don’t put 3D printing in the title. This is great; 3D printing isn’t a fascinating new technology that’s the first step towards Star Trek replicators; we’ve slid down the trough of disillusionment and now 3D printers are just tools. It’s great, and in 2018 things are as they should be.

You Can’t Build A Roland TR-808 Because You Don’t Have Faulty Transistors

That headline sounds suspect, but it is the most succinct way to explain why the Roland TR-808 drum machine has a very distinct, and difficult to replicate noise circuit. The drum machine was borne of a hack. As the Secret Life of Synthesizers explains, it was a rejected part picked up and characterized by Roland which delivers this unique auditory thumbprint.

Pictured above is the 2SC828-R, and you can still get this part. But it won’t function the same as the parts found in the original 808. The little dab of paint on the top of the transistor indicates that it was a very special subset of those rejected parts (the 2SC828-RNZ). A big batch of rejects were sold to Roland back in the 1970’s — which they then thinned out in a mysterious testing process. What was left went into the noise circuit that gave the 808 its magical sizzle. When the parts ran out, production ended as newer processes didn’t produce the same superbly flawed parts.

This is an incredible story that was highlighted in 808, a documentary premiered at SXSW back in 2015. The film is currently streaming on Amazon Prime (and to rent everywhere else) and is certainly worth your time just to grasp how seminal this drum machine has been in hip hop and several other music genres.

For modern product developers, betting your production on a batch of reject parts is just batty. But it was a very different time with a lot fewer components on the market. What worked, worked. You do have to wonder how you stumble upon the correct trait in an obscure batch of reject parts? Looks like we’ll be adding Ikutar Kakehashi’s book I Believe in Music: Life Experiences and Thoughts on the Future of Electronic Music by the Founder of the Roland Corporation to our reading list.

[via EMSL]

Restoring A Piece Of Musical History

Every restoration project involves various levels of grit, determination, gumption and doggedness. But [Darren Glen]’s restoration of a Jupiter-8 is an absolute labor of love. The Jupiter-8,  launched by Roland in 1981, was their flagship “polyphonic analog subtractive” synthesizer and was used by many legendary acts of the ’80’s. The synthesizer was rugged — built to withstand the rigors of travelling everywhere that the bands took it. More importantly, it could produce a wide range of sounds that came from dedicated and independent controllers. These, plus a host of other desirable features, makes the synth highly coveted even today and the rare ones that surface for sale can be quite expensive.

The back story of how he came in possession of this coveted, albeit non-functioning, piece of history is a good read. But the part that makes us all interested is the meticulous restoration that he is carrying out. There is a lot of useful information that he shares which could be handy if you are planning any restoration project of your own.

When he first turned it on, all he got was an “8” on the display — which seemed like an error code. From then onward, he has been carefully stripping away each part and slowly bringing it back to life. All of the linear slide potentiometers and slide switches were de-soldered, dis-assembled, cleaned of rust and the carbon tracks and contacts cleaned with special spray — making them almost as good as new. The transformer and its mounting brackets received a similar treatment of rust cleaning and fresh paint. All of the other internal metal parts, such as the chassis, were restored in a similar fashion.

White plastic buttons and knobs which were faded, were brightened up by spraying them with a generous dose of hydrogen peroxide hair spray, putting them in Ziploc bags and letting them bake in sunlight for a day. [Darren] was satisfied enough with this process and gave the same treatment to all the other colored buttons too, with good results. The other set of plastic parts – the keyboard keys, were cleaned and polished with a scratch and blemish polish cream, and replacements were ordered out from a specialist supplier for the few that were damaged beyond repair.

But by far the greatest challenge for [Darren] has been resurrecting the top metal cover. It was badly rusted and had to be completely stripped of all paint. Repainting it the right shade was relatively easy, but applying the legend and decals took him to every screen printer in town, none of whom could manage the job. He lucked out by locating a screen printer who specialized in custom automotive work and managed to do a pretty good job with the decal work.

The Z80 microprocessor had lost all its magic smoke, so [Darren] has ordered an original Zilog replacement which will hopefully clear the error he noticed when it was first turned on. He’s slowly working his way through all the issues, and it is still work in progress, but we look forward to when it’s all done and dusted. A fully functional, restored Roland Jupiter-8 — one of the first 500 that were built back in 1981 — resurrected with a lot of TLC.

A big shout out to [Tim Trzepacz] for bringing this project to our notice.

A Six-Voice Synth Built On The Raspberry Pi

Over the last few decades, audio synthesizers have been less and less real hardware and more and more emulations in software. Now that we have tiny powerful computers that merely sip down the watts, what’s the obvious conclusion? A six-voice polyphonic synthesizer built around the Raspberry Pi.

The exquisitely named ‘S³-6R’ synthesizer is a six-voice phase modulation synthesizer that outputs very high resolution (24-bit and 96 kHz) audio. It’s the product of R-MONO Lab, who have displayed interesting musical devices such as a recorder-based pipe organ in the past. This build is a bit more complex, offering up some amazing sounds, all generated on a Raspberry Pi 3.

While talk of oscillators and filters is great, what’s really interesting here is the keyboard itself. The S³-6R is using the Roland K-25m, a tiny MIDI keyboard meant to serve as a ‘dock’ of sorts for Roland’s recent re-releases of the classic Jupiter and Juno synths. Building a MIDI keyboard is not easy by any stretch of the imagination, and using this little keyboard dock is a cheap way to pipe MIDI notes into any project without a lot of fuss.

Below, you can check out the audio demos of the S³-6R. It’s a real synth and sounds great. We can only hope the software will be uploaded somewhere eventually.

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A Robotic 808 Drum Machine

If you spent the 1980s hanging out at your local record store, and you don’t have a hankering for spandex and bouffant rock-god hairstyles, the chances are you’ll have more than a few pieces of electronic music from the period in your collection. The proliferation of electronica during that era came through the arrival of relatively inexpensive mass-market digital polyphonic instruments, edging out the sounds of monophonic analog synthesisers for a subsequent generation to rediscover in a later decade. Individual instrument models became icons and entered the musical vernacular of the day, the Ensoniq Mirage sampling synthesiser, the Yamaha DX7 FM synthesiser, or the Roland TR-808 drum machine.

It is the Roland TR-808 that inspired today’s subject, the MR-808 robotic drum machine, from [Moritz Simon Geist]. A percussion sequencer featuring real instruments all built into a cabinet styled to resemble a huge Roland 808. Originally built as a performance instrument, but since reinvented as a piece of installation artwork that visitors can program for themselves.

Block diagram of the MR-808
Block diagram of the MR-808

There is a comprehensive description of the machine’s design and build on the creator’s website, as well as a more high-level introduction. A significant amount of effort was put in to creating mechanical instruments as close as possible to the Roland sounds, with each instrument being operated by solenoids driven by a MIDI-controlled Arduino Mega. A second Arduino, this time an Uno, controls lighting that follows the instruments.

The interactive part of the installation comes from a sequencer front-end running in a web browser on a Nexus 7 tablet, this appears to be served from a Raspberry Pi which supplies MIDI to the MR-808.

The results can be seen in the video below the break, and judging by the reaction of the audience the machine is rather popular.

Continue reading “A Robotic 808 Drum Machine”

Upgrading Old Synths To OLED

Roland’s Alpha Juno 2 is an analog, polyphonic synth made in the mid-80s. While it isn’t as capable as the massive synths made around that time, it was very influential synth for the techno scenes of the late 80s and early 90s.

[Jeroen] is lucky enough to have one of these synths, but like all equipment of this era, it’s showing its age. He wanted to replace the character LCD in his Alpha Juno 2 with an OLED display. The original character LCD was compatible with the Hitachi HD44780 protocol, and still today OLEDs can speak this format. What should have been an easy mod turned into editing hex values on the EEPROM, but he still got it to work.

While the original character LCD could display one line of 16 characters, the ROM in the synth didn’t know this. Instead, the display was organized as a 2×8 display in software, with line one starting at address 0h, and line two starting at 40h. For a drop-in replacement, [Jeroen] would need a display the characters organized in this weird 2×8 format. None exist, but he does have a hex editor and an EEPROM burner.

With the Alpha Juno’s firmware in hand thanks to someone who does a few firmware hacks to this synth, [Jeroen] had everything he needed. All that was left to do was going through the code and replace all the references to the second line of the character LCD.

After burning and installing the new ROM, the OLED display was a drop-in replacement. That meant getting rid of the whiney EL backlight in the original display, and making everything nice and glowy for a few nights on a dark stage.