Transistor radio series – The 7 MHz scratch synthesizer


Vasily Ivanenko has written up documentation on his 7 MHz synthesizer project:

Above — All 4 boards were built in re-purposed Hammond boxes. A PIC-based counter sits on top of the offset mixer. I build modular gear and this allows modification and fosters experimentation. When I build a final transistor radio receiver, I plan to place the offset mixer, PLL circuitry and VXO on the same board inside the radio with some shielding. My VCOs always go in a RF tight container. A 0.0033 µF feed through capacitor connects the VCO varactors to the outside world.

See the full post on his blog, QRP HomeBuilder.

The microTS – Smallest synth in the world


MicroTS, a smallest synth in the world from DIY synthesizer:

The micro-TS is a key fob sized DIY synthesizer (61x41mm) with actually useable knobs like an analog synthesizer. The ball pen is for size reference.
It has a one octave touch keyboard, 6 knobs and a stereo headphone output.
Running on a CR2032 button cell battery it is the smallest playable and programmable synthesizer in the world.

Project info at Janost’s blog.

Check out the video after the break.

MIDI DAC for Vintage Synth Hacks

A lot of classic synthesizers rely on analog control voltages to vary parameters; this is a problem for the modern musician who may want to integrate such hardware with a MIDI setup. For just this problem, [little-scale] has built a MIDI-controllable DAC for generating control voltages.

It’s a simple enough build – a Teensy 2 is used to speak USB MIDI to a laptop. This allows the DAC to be used with just about any modern MIDI capable software. The Teensy then controls a Microchip MCP4922 over SPI to generate the requisite control voltages. [little-scale]’s video covers the basic assembly of the hardware on a breadboard, and goes on to demonstrate its use with a performance using the MIDI DAC to control a Moog Mother 32 synth. [little-scale] has also made the code available, making it easy to spin up your own.

We can see this project being indispensable to electronic musicians working with banks of modular synths, making it much easier to tie them in with automation in their DAW of choice. This isn’t the first MIDI interfacing hack we’ve seen either – check out this setup to interface an iPad to guitar pedals.

Filed under: musical hacks

Adding MIDI Out to the Casio PX410R

Since the 1980s, MIDI has been a great way to send data between electronic musical instruments. Beginning as a modified serial interface running through optoisolaters and DIN sockets, these days, your hardware is more likely to carry its MIDI data over USB instead. This is great if you want to hook up to a computer without a cumbersome interface, but not so great when you want to connect a bunch of instruments to each other.

The Roland Integra 7 is a rack mount synthesizer with classic MIDI ports. [adriangin] wanted to control the synthesizer over MIDI, but their Casio keyboard only had MIDI over USB available. To get around this, [adriangin] set out to add a standard MIDI Out port to the Casio PX410R.

If you want to be a hardware hacker, get familiar with standard serial communications. After some probing around the test pads while playing with the keyboard’s sustain pedal, [adriangin] found what looked like a MIDI signal between two ICs, but at a non-standard bitrate. The hunch turned out to be correct – the signal was going between the synthesizer DSP chip & the IC handling the USB connection. The standard MIDI interface operates at 31250 baud, while this signal was at 215500 baud. There’s no simple way to convert from one baud rate to another, so [adriangin] had to do it the hard way.

An Atmega32P was pressed into service, using a soft UART implemented on a digital pin to run at 215500 baud. At such a high bitrate, the soft UART required some cycle-accurate assembly programming to get everything humming along. The data would then be repeated over to the hardware UART running at 31250, which was wired to a standard DIN plug as used in classic MIDI. It’s a useful hack that allows the keyboard to work with a much wider range of hardware. It’s topped off by its clean execution, with the new port neatly integrated into the rear panel.

Check out these other great MIDI hacks, like this chiptune looper built from the ground up or this MIDI-enabled Stylophone.

Filed under: musical hacks

Gecho Pocket Synth Looper

[Mario] wrote us with his synthesizer project that’s currently up on Kickstarter. It looks like a good amount of fun to play with, as you can see in the video on the Kickstarter page. But it’s also built to be easily hackable.

On the hardware front, it’s a tiny four-layer board that’s crammed with parts. At the core is an STM32F4 microcontroller and a DAC. Indeed, the build was inspired by other folks’ work on the STM32F4 Discovery dev kit that has been used to make some pretty interesting synthesizer devices. [Mario]’s version adds two stereo headphone outputs, two microphone inputs, two IR reflective distance sensors used as control inputs, some buttons, and a ton of LEDs. And then it makes good use of all of them.

The firmware isn’t open source yet (poke! poke!) but it looks like it’s going to be. On his blog, [Mario] works through an example of adding a drum machine into the existing firmware, so it looks like it’ll be hackable.

Squeezing a lot of DSP functionality out of a single microcontroller is a feat. On a similar chip from a different manufacturer, [Paul Stoffregen]’s Teensy Audio Library could also be made to do a lot of the same things. But the real beauty of the Gecho project is that it has some interesting hardware features already built in and ready to go. It wouldn’t be a bad launching pad for your own musical or audio explorations.

Filed under: Microcontrollers, musical hacks

Sporty Cars Making Fake Engine Noise

Following the monumental emissions-cheating scandal at VW, further horrible revelations demonstrate just how corrupt the modern automotive industry has become: many cars make fake engine noise. And we’re not just talking about those darn sneaky Priuses.

Ford, BMWs, Porsche, and yes, Volkswagen are all doing it, to different degrees. Some of the systems, like the one in the BMW M5, play engine sounds at low volumes through the stereo system. As you’d expect from a BMW, it’s an overly-technological solution: they have built essentially a BMW engine-sound synthesizer that responds to the tachometer and gas pedal data from the car’s data bus. They also let you turn off the “acoustic experience”.

To our taste, the Porsche Sound Symposer and Mustang Boss 302 systems are a little more honest. The former has an actual additional pipe in the exhaust system that (optionally) allows authentic engine sound into the cockpit. The Mustang adds extra resonant tubes to the exhaust, running alongside the mufflers. There’s a restrictor plate that separates them, limiting the amount of extra noise produced. Remove this plate, and you’ve got a noise monster.

These cars are all victims of their own success. The BMW’s frame is so good at noise damping that it became eerie to drive for some enthusiasts. All of the engines run quieter and more efficiently than their gas-guzzling predecessors.

But we’re in this strange transitional period where the tech has outpaced our own preconceptions of power. People still want the roar, even though cars with silent electric motors are going to be beating gas guzzlers out of the blocks as a matter of course in the very near future. You just can’t beat the starting torque of an electric motor (without burning out your clutch).

Our guess is that future generations will look back and laugh. That said, we’re all still taking photos with CMOS sensors that have a speaker attached just to go “click” and the old-timey phone bell ringtone is still going strong. People are funny.

Thanks [Jack Laidlaw] for the tip!

Filed under: car hacks

The Most Flexible Synthesizer is DIY, Raspberry Pi

[Ivan Franco] sent us this great synthesizer project that he’s working on. Or maybe it’s more like a synthesizer meta-project: a synthesizer construction set. You see, what Pryth has is a Raspberry Pi inside that’s running a custom distribution that includes SuperCollider to generate the sound, OSC for the communication layer, and a Teensy with up to 80 (!) multiplexed analog inputs that you’ll connect up to whatever hardware you desire.

With the computer inside the box — the Raspberry Pi in question — you can easily make this system into a standalone musical instrument, without tethering it to your laptop. Or you can tether it, and using a web interface that’s hosted on the Pi, write new SuperCollider programs for your instrument, changing the way it behaves. And of course, if you’re already a SuperCollider or Raspberry Pi expert, you can work on the Pi directly.

The system is brand new, but check out the Mitt synth device that [Ivan] already made, with a video embedded below. It’s a good overview of one of the possible hardware configurations, and a sweet demo of a couple SuperCollider routines.

[Ivan] is trying to create an interesting and easy-to-use empty vessel for you to pour your hardware and software synthesizer dreams into. Everything is open source, and aside from the Pi and the price of potentiometers, this is a dirt-cheap device. You’re not going to be limited by SuperCollider, and we’re guessing that you’re not going to be limited by 80 inputs either. What’s the craziest sound-maker you can think of?

Filed under: musical hacks

Not Just Another Alarm Clock

Even though [Stefan] sent in this link with the heading “Another Sunrise Alarm Clock“, it’s anything but plain. Sure, from the outside it looks like a simple and refined design, but the story of getting there is hardly straightforward.

chordegg2015tonegenTake that nice-looking luminous dial. [Stefan] made it himself, using the same techniques that he’s used for making his own watch faces. (Amazingly, he prints them out on a color ink-jet.) This is a sunrise wake-up clock, but if the bright LEDs don’t wake him up, there’s also a vintage DIY synthesizer project stuffed in the box in place of a cheap piezo buzzer. Even the wooden case shows attention to detail — it has nice edging done on a router table.

So yeah, we’ve all seen clocks before. But this one is very personal, melding together a few of [Stefan]’s hobbies into one useful, and good-looking, device.

Filed under: clock hacks

VXO – based PLL frequency synthesizer for 7 MHz


Vasily Ivanenko made a VXO-based synthesizer:

To make a VXO to mix with a ~7 MHz VCO, you’ll need a crystal that is higher in frequency than the highest frequency you want to synthesize. Some rummaging revealed a bag of 21.4773 MHz crystals that I could divide by 3 to garner 7.159 MHz.
To afford a reasonable delta F, three were placed in the super VXO fashion and I applied the smallest amount of series inductance that would ensure a reasonable delta F with solid frequency stability.

Full info at QRP HomeBuilder blog.

Radionova 1 frequency synthesizer


Vasily Ivanenko has written up documentation on his Radionova 1 frequency synthesizer project:

Frequency synthesizer for my Jupiter receiver — Радионова 1 — [ Radionova 1 ]
Greetings! Most of my future homebrew radio projects will focus on building radio astronomy gear.
Radio astronomy offers much fun + learning for the radio homebuilder — example topics include how to design and make antennas, LNAs, receivers, and frequency synthesizers from HF to microwave. Further we may craft op-amp analog integrators to remove background noise, and/or ADCs, plus write software to store and analyze our data. Avid radio astronomers enjoy a strong understanding of noise measurement/physics, plus a whole lot of really cool science. I’ve already made new friends and feel inspired by the dedicated, skillful folks who listen to signals from space on stuff they craft in their home labs. In radio astronomy, Dx might mean receiving signals from 590 million kilometers away. I’m in!

Project info at QRP HomeBuilder blog.