A Transistor-less Sound Synthesizer

A synthesizer without transistors could almost be the basis of a trick question, surely without transistors it must be using a vacuum tube or similar. Not [Dr. Cockroach]’s synth though, instead of transistors it uses coupled pairs of LEDs and light-dependent resistors as its active components. Its oscillator circuit comes courtesy of [Patrick Flett], and uses a pair of LED/LDR combinations to alternately charge and discharge a capacitor. This feeds another LDR/LED pair that appears to act as a buffer to drive a bridge rectifier, with a final amplifier following it.

The result oscillates, though at frequencies in the low audio range with a cluster of harmonics thrown in. Its sound is best described as something akin to a small single-cylinder motorcycle engine at the lower frequencies, and is something we see could have all sorts of interesting possibilities.

This approach of using LDR-based active devices may be something of a dead end that could have had its day back in the 1930s, but it’s nevertheless an entertaining field to explore. It’s not the first time we’ve followed [Dr. Cockroach] at it, in the past we’ve seen the same technique applied to logic gates.

Have a listen to the synth in the video below the break. Continue reading “A Transistor-less Sound Synthesizer”

This Synth Plays The Only Scale Everybody Knows

[randomprojectlab] is building a synthesizer around the pentatonic scale for the Hackaday Prize. It’s the Pentasynth, and it’s basically just a keyboard with five notes per scale.

There’s something common to every form of music. Nearly every musical tradition, from western art music, to Indonesian folk music makes use of a pentatonic scale. This is just a major scale without fourth and seventh scale degrees, or just playing the black keys on a piano.  It’s the one scale everybody knows, and forms the basis of every school of thought for music education. Noodling over the pentatonic scale is what all the cool guys do in Guitar Center. It’s absolutely the foundation of all music.

The hardware for this build is an Adafruit Metro Mini, or basically an Arduino with an ATMega328. This generates three channels of audio, two square waves — one each for the keyboard and bass accompaniment — and a pseudo-random noise drum beat. The keys are 3D printed, and the enclosure is CNC’s acrylic.

Most educational music toys out there have a few additional bits to make composing music easier. The Pentasynth is no exception, with a button that adds a drum beat, a button that adds a bassline, and a switch that makes the keyboard major or minor. It’s a great idea, and you can check out a video of the Pentasynth in action below.

Continue reading “This Synth Plays The Only Scale Everybody Knows”

Tiny-TS: Just How Small Can A Playable Synethesiser Get?

The early electronic synthesizers were huge machines, racks of electronic modules that filled entire rooms. Integration of electronics over time successively reduced them, first to the size of a large piece of furniture, then to  tabletop consoles, to standalone keyboards, and to small MIDI black boxes taking their instructions from another instrument or a computer. The original mass of discrete electronics had been reduced to a pile of ICs, then chipsets, then finally single ICs and software implementations on microcomputers.

It’s thus possible to make a synthesizer these days that is pretty small. If you can fit a microcontroller in it, you can fit a synth into it. But how about a playable synthesizer? One with a keyboard, on which you can give a recital? How small can you make one of those? [Jan Ostman] has a contender for the smallest playable synthesizer prize with his Tiny-TS, a credit-card synthesiser with a one-octave capacitive keyboard and analog controls for synthesis parameters.

The heart of the synth is an ATMega328, for which he provides the software. The parameters adjustable by a series of pots are listed as DCO: Coarse pitch and Double, DCF: Filter peak and ENVmod, and ENV: Attack and Release affecting amplitude. You can build your own, or he tells us that he has the project up as a Kickstarter campaign if you fancy the chance of buying one ready-made.

In case you are wondering, it doesn’t sound too bad. Some minimalist synths sacrifice the breadth of sounds they can create, but not this one. He takes it through its paces in a YouTube video which we’ve put below the break.

Continue reading “Tiny-TS: Just How Small Can A Playable Synethesiser Get?”