Bringing Guitar Synthesis To The Microcontroller

If you’re working with audio in an embedded environment, the best option for years now has been the Teensy 3 microcontroller board. This choice has mostly been due to its incredible power and audio libraries, but until now we really haven’t seen a stompbox-style interface that used the Teensy to its fullest extent. Now we have, in [Wolkstein]’s GitSynth, everything you could want in a synthesizer that processes the signals from an electric guitar.

The core of this build is a Teensy 3, and all the audio goodies that come with that. Also included is a USB MIDI and audio interface, smartly both attached to a panel-mount USB-B connector on the back of the stompbox. Other controls include a single mono in jack for guitars and synths, two mono out jacks for stereo-ish output, a bunch of footswitches for bypass, tap tempo, preset selection, a jack for an expression pedal, and some buttons to move around the LCD user interface.

While putting a powerful microcontroller in a stomp box for is a project we’ve seen many times, this project really shines with the MIDI GUI that’s built for a device with a real display and a mouse. [Wolkstein] built a PyQt-based app for this synth, and it’s a plethora of buttons and sliders that looks similar enough to a real synthesizer. There’s enough configurability here for anyone.

You can check out the demo video (in German, but auto-translate subtitles exist) below.

Thanks [Mynaru] for the tip!

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Guitar Mute Pedal Made From Upcycled Parts

Rockin’ out on your fave guitar is pretty fun for sure but whether your on stage or jamming in your basement, it can be convenient to quickly mute those killer licks. [wozlaser] wanted a mute pedal for his guitar and instead of shelling out the tens of dollars for a commercial version, he decided to build one himself.

This pedal is heavy-duty and made out of metal. If the frame looks familiar, that is because in a prior life this was a control pedal for a sewing machine. [wozlaser] found it cheap at a thrift store. After the internals were taken out, he added a few key parts. First were the 1/4″ input and output jacks that were scavenged from an old stereo system. There is a momentary switch from a VCR and a standard guitar stomp pedal switch mounted all the way in the front of the frame. The wiring is as follows:

DIY guitar mute pedal

The wiring schematic is pretty darn simple, it just grounds and ungrounds the signal wire. As stated earlier, there are 2 switches, a momentary and a push-on/push-off switch. A normal mute pedal would only have one switch but [wozlaser] wanted something special. If you push the pedal all the way forward it will mute or unmute the signal until it is pushed again. When the pedal is in the spring-supported ‘up’ position a lever pushes on the momentary switch, a slight push on the pedal lifts the lever off of the momentary switch to mute or unmute the signal. The function of the momentary switch (mute or unmute) changes with the state of the other switch. This works exactly the same as a 3-way light switch circuit allows two switches to control one light in your house. With this setup [wozlaser] is able to not only mute and unmute his guitar but strum a chord with it off and pulse the chord on to the beat of the music or tap the pedal with some guitar feedback to make the sound cut in and out. All that only cost [wozlaser] a little time and spare parts… and there are no batteries to replace!

Fabbing a guitar tremolo stompbox

There’s a lot of builders around whose first foray in electron manipulation was building effects pedals for guitars. It looks like [Dino] might be getting back to his roots with his tremolo effects box how-to.

Last week, [Dino] found an old 5-watt tube amp in someone’s trash and decided to bring it back to a functional state. With his new trem effect, it looks like [Dino] might be getting the band back together.

Apart from tiny boost circuits, a tremolo is generally the simplest effect pedal you can make. All you’ll need to do is vary the amplitude of the guitar’s signal at regular intervals. After that, it’s only a matter of pretending you’re playing through a rotating Leslie speaker.

To get his trem working, [Dino] set up a 555 circuit to flash a LED at regular intervals. This LED is encased in heat-shrink tubing along with a photocell. This setup controls an LM386 amplifier. The build is really simple, but from the video after the break we can tell it sounds great.

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Coyote-1 guitar pedal available now

OpenStomp’s Coyote-1 is now available for $349. The guitar effects pedal lets users design and upload their own effects to the device. It has two stomp switches with LEDs, an LCD display, and four user assignable knobs. The back has 1/4″ in/out and one selectable 1/4″. It also features NTSC composite out, a headphone jack, mini-USB for uploading, and an RJ11 I2C bus for expansion. The processor is a Parallax Propeller Chip. While the OS on the pedal is open source, the hardware design and effect design software are not. You can check out the source and product manual on their forum. If you’re more interested in breadboarding hardware, you might like the Beavis Board we covered earlier.

[via Create Digital Music]

In car WiFi

You may have already heard that Chrysler is planning to provide in-car wireless internet access to its vehicles. If not, expect to hear more about it later this year when the requisite hardware becomes a sales-floor option, or next year when it becomes factory standard for some cars.

We can’t say it’s a bad idea, it’s just not a new one. Plenty of commercial portable routers are available, but they still need a modem and data plan to provide internet access. For internet access and wireless routing, look to [Nate True]’s cellphone-router combo, which uses a spare Nokia cellphone and a highly modded Wi-Fi router running OpenWRT. [True] has made it easy by providing the instructions and necessary custom code, but it seems like a lot of effort for a relatively slow connection. We think the original Stompbox is still the most fun since it has the speed of commercial devices and an open x86 OS to modify.