One Bit Sound With The ZX Spectrum

[Michael] has a thing for playing audio over beepers using a single bit. He’s done it with the Apple ][ and the IBM PC. This time he turns to the ZX Spectrum. He didn’t get quite as good a result — at least not yet — but he did manage to get some things working. He documents everything, so even though this wasn’t a successful week, there’s sometimes more to learn from reasonable failures than from unreasonable successes.

Of course, the whole thing relies on pulse code or pulse width modulation. Of the two techniques, PWM should produce better results. However, he wasn’t able to get PWM working yet. Some other target computers drive the buzzer through a dedicated hardware timer. However, with the Spectrum, it is all software.

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This Clavichord Is A Well-Tempered Project

The Clavichord needs no introduction to fans of Early Music, and a lengthy one to literally everyone else. Even classical music buffs who have heard of Bach’s works for the “Well-Tempered Clavier” — another word for clavichord — will mostly have heard them performed on Piano. That is perhaps fitting, as the clavichord is a distant ancestor of the modern piano. It has keys — though fewer of them than a piano — whose action strikes strings — though much, much fewer of those than a piano, as each string is required to generate multiple notes. [Ian Summers] has an excellent guide on how he built his, though be warned that that link goes to a PDF and the SSL certificate was having problems as of this writing. If you aren’t comfortable grabbing a PDF over old-style HTTP, we’ve embedded the demo/build video below so you can give a listen to what this pre-piano instrument sounds like.

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Miniaturized, Working Replica Of Vintage Leslie Speaker

Few pieces of vintage audio gear from the turn of the century (the previous one) inspire the kind of devotion that a Leslie speaker does. Sure, there are plenty of pieces that are rarer or more valuable, but the Leslie speaker has such a big following because of its uniqueness of physically moving sound around a room. Two rotating devices in the speaker physically direct the sound around the cabinet with musician-controlled speed, and this sound remains extremely difficult to reproduce faithfully without the moving components. But originals are enormous and meant for organs, so [Eric] built a 40% replica with a few modern touches for his guitar.

The build starts with a CAD model, where [Eric] works towards making the most accurate enclosure for his speaker as possible. The CAD model heads out to a CNC machine which can care most of the details into the wood, and he eventually is able to finish it, although it took a few tries with stains and paintbrushes of various types. For the speakers themselves, he’s using modern versions including modern brushless motors to drive the rotating elements. Like the original speaker, the high range of sound is sent through a rotating set of horns, of which one is only a counterweight, and the low range is directed out of the bottom of the cabinet through a large rotating drum. Both rotating elements here are 3D printed, and with everything put together and wired up [Eric] has a much more portable, faithful recreation of the original Leslie speaker.

There are some upgrades in the wiring too, which makes it work better with a guitar rather than for an organ. It’s also much lighter, and was a hit when he took it to let a few other guitarists to play as well. It’s not the first time we’ve seen the Leslie’s movement recreated for guitar, but it is the most alike to the classic 1930s-era speaker we’ve seen so far.

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3D Printed Piano Action Faithful To The Original

A piano’s internal mechanism for translating a key press into sound is surprisingly complicated. It has to do a lot of things simultaneously and quickly: provide precise control over velocity, ensure the hammer doesn’t press itself against the strings,  ensure the hammer rebounds without accidentally hitting the strings, allow for quick, continued strikes of the strings, and dampen the string after the key is released. Not only is that a mouthful to say, it’s a tall order for a mechanical device and took (arguably) around 150 years for the idea to be refined into what most of us would recognize as a piano. But could [dovetail] do it with a 3D printer in a few weeks?

[dovetail]’s design relies on compliant mechanisms, which are solid parts that flex in specific and controlled ways to provide movement. The action took many iterations to make sure that all of the feelings of all the parts of a real piano action were accounted for in this model. Pianos have more than one key, though, so [dovetail] also had to design a modular system to piece all the keys together. The modularity extends to the piano’s electronics as well, with a set of PCBs daisy-chained together, each of which supports a set of keys. This is a hybrid piano, a style with a real action but digital sound production. Using infrared sensors allows the instrument to behave as a MIDI keyboard, but one with the goal of feeling somewhere between a digital piano and a fully analog one.

The piano was first demonstrated at Open Sauce, where a number of musicians were able to try it out. As a prototype device it still has a few rough edges that [dovetail] plans to improve upon, like changing the sensors from IR to hall effect, improving the action and using a different filament. There are some other things he has planned as well which we look forward to seeing in future videos. And, although a completely different instrument, it has a number of similarities to this action built to strike a bass drum instead.

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Encoding MOD Files Optically On Paper, Because Amiga’s Legacy Will Outlast M-Disks

All but a few of our very youngest readers are surely familiar with music formats that rely on optical disks. When we say [RobSmithDev] made a MOD tracker that uses an optical disk, then, you might be forgiven for thinking he stuck a bunch of MOD files onto a CD– MOD files being a format of electronic music that was conceived of on the Commodore Amiga that is still used to this day. A dedicated MOD-CD player might be a fun project, but it’s not what [Rob] did; his project is far more impressive and impractical, as he’s come up with a way to encode the MOD files on paper for optical playback. This way the Amiga’s legacy can be preserved longer than the paltry thousand years promised by the optical M-disk format.

Zooming way, way in on the disk reveals that he’s actually printing the patterns of the MOD file row by row, just like you’d see playing it in a ‘tracker’ program. A MOD file, you see, does not encode music like a WAV or MP3. Rather, like with MIDI, it lists the notes the software reading the file — traditionally called a tracker — is to recreate. Unlike a MIDI file, though, you don’t have to store the same notes more than once: repeating sections are stored in patterns. So most of the disk is just a long list of hexadecimal numbers: several columns worth, one for each ‘voice’ or instrument playing in the song. Another difference with MIDI is that MOD files are self-contained in that they are supposed to contain the samples, which isn’t in evidence until you flip over the disk.

There’s no B-side to [Rob]’s album. Instead a QR-code like series of barcodes is used to encode the samples used in each track on the disk, as well as other information needed to recreate the MOD file, including metadata like title and artist, and the sequencing of the patterns on the front. Of course this means he needs two cameras on his physical mod player, one on each side, and steppers to slide them across the disk like a linear tracking turntable. The front is read via OCR of his modified Amiga “Topaz” font, while the rear holds the first 1084 bytes of the MOD file in a QR-inspired format [Rob] produced specifically for this project.

Unlike the last time we saw someone store music in QR codes, the more modest size requirements of modfiles — something that led to their use in keygens — means this player can store the music’s 8-bit sound samples without the OPUS compression [Rob] is using affecting fidelity. He’s working on another video to give the details of the player– as he works out the bugs, right now it can’t jump betwixt patterns on the disk as fast as some modfiles need–but we’re willing to hazard a guess he’s got a Raspberry Pi in there, and that it’s probably not running the Amiga-inspired AROS operating system.

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An Electronic Explanation Of 1960s Fuzz Boxes

It’s likely that even those of us who have never picked up a guitar in our lives will recognize the sound of an electric guitar with a fuzz box effects pedal. The raspy distorted sound has been at the heart of so many very well known recordings. Behind it is a distortion circuit, or as [Bill Jehle’s Mad Scientist Guitar Lab] is here to tell us, eight different circuit topologies.

The result is a fascinating trip through the evolution of rock music through the 1960s, as he examines circuits from simple diode clippers through to frequency doublers and phase shifters. He’s provided a playlist as an accompaniment so you can even have an immediate listen to each sound. It’ll mess up our YouTube recommendations, but worth it for the informative journey.

It’s also a window into a lost period in electronics where all they practically had was the transistor, so each device had to put in the maximum work for a living. Designing circuits like these called for intimate knowledge of the device characteristics, and just how they could be safely exceeded. The video is below the break, and well worth a watch.

If clever transistor music circuits interest you, you’ll love the flawed devices that gave the Roland 808 its sound.

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Building A Hammond Organ To Understand How They Work

The Hammond organ is an early form of electronic– or perhaps electromechanical– musical instrument. It solved the very real problem of organs normally being the sort of thing you built into a cathedral, allowing a similar sound to fit into a piano-like form factor. Their workings are a so simple that it’s hard to wrap your head around it actually working– which is why [Uri Tuchman] built one on YouTube. Also for a gift exchange, but we’re not Santa, here– we’re here to learn, and [Uri] does not disappoint.

[Uri]’s organ is a bit smaller than what the Hammond corporation was putting out back in the day, just one hand-cranked octave– and it lacks the distinct spinning speaker in favour of plugging into any old guitar amp. It’s enough to get the idea across. Each of the twelve keys acts as a simple switch, wired to a pickup made from a coil of wire around a steel rod– much like a magnetic pickup on an electric guitar. The pickup faces the tone wheel, which is the part that feels like magic: the tonewheel spinning past the pickup acts exactly like the steel string vibrating in an electric guitar, its ferroelectric motions inducing a tiny current. The tonewheels smooth teeth are spaced to create sine waves at the frequencies corresponding to each key, so it has to be exact. That’s why while the rest of the brass-and-wood build is [Uri]’s beautiful craftsmanship, the iron tonewheels are CNC’d.

Aside from the amp it is plugged into, there are no electronics here. There’s nothing to double or otherwise alter the frequencies: one key means one tonewheel– twelve for this build– and if the RPMs are off everything is out of tune. Good thing [Uri] made it hand-cranked! Well, it is for a gift exchange. Maybe it’s a white elephant sort of thing, because we can only imagine that making it much harder to play. On the other hand, [Uri] demonstrates some neat effects by varying the RPM at the end of the video, so perhaps that’s a feature.

As nice as [Uri]’s work is, Hammond Organ Company filmed the construction themselves, back in the day if you want to see the true quill. Alternatively, you can get more of [Uri]’s craftsmanship with this square guitar.

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