Mechanical Tremolo Does Things The Old-School Way

The word “tremolo” has a wide variety of meanings in the musical lexicon. A tremolo effect, in the guitar community at least, refers to a periodic variation in amplitude. This is often achieved with solid state electronics, but also recalls the sounds created by Hammond organs of years past with their rotating Leslie speakers. [HackaweekTV] decided to do things the old fashioned way, building a mechanical tremolo effect of his own (Youtube link, embedded below).

Electronically, the signal is simply passed through a linear audio potentiometer. The effect is generated by rapidly cycling this potentiometer up and down. The motion is achieved through a geared motor salvaged from a Roomba, which turns a cam. A sprung follower sits on top of the cam, and is attached to the potentiometer.

There were some challenges in development. Rigidity of the frame was an issue, and the follower had issues with snagging on the cam. However, with some careful iteration they were able to get everything up and running. The final project sounds great, and with the amplifier turned up, there’s no need to worry about the sound of the moving parts.

Naturally, you can always build a tremolo with a 555 instead. Video after the break.

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Wah-Wah-Won’t, To Wah-Wah-Will

This is the tale of [Chris], who discovered he was no [Jimi Hendrix] in his youth, and shelved his trusty wah-wah pedal as a result. Many years later as a bassist with more modest aims he brought it out of retirement and built a blend pedal kit to allow him to bring in a bit of wah to the mix when he wanted it, but as more of a Voodoo Grown-Up than the full Voodoo Chile.

The kit worked and he should have been happy with it, but for one thing. As he increased the mix on the loop box instead of getting more wah he simply got less volume. A bit of detective work reached the conclusion that the old pedal was inverting everything, and that he needed to put in a circuit to correct that when needed. A single op-amp and a switch, with the op-amp circuit dead-bug-style on the back of the switch, completed the modification.

Wah pedals seem to be a recurring feature here. We’ve brought you one made of Lego among many others, as well as one repurposed as a synth controller.

Hackaday Prize Entry: DIY Guitar Multieffects

Guitar effects and other musical circuits are a great introduction to electronics. There’s a reason for this: with audio circuits you’re dealing with analog signals and not just the ones and zeros of blinking a LED. Add in the DSP aspects of audio effects, and you have several classes of an EE degree wrapped up in one project.

For his Hackaday Prize entry, [randy.day] is building a guitar multieffect. Instead of just a single distortion, fuzz, or chorus circuit, this tiny little PCB is going to have several flavors of pitch shifting, a flanger, chorus, echo, harmony, and stranger ‘digital-ish’ effects like bitcrushing.

This effects unit is built around a PIC32 and a TI audio codec which processes the audio at 64k 32-bit samples/second. This takes care of all the audio processing, but the hard work for a guitar pedal is actually the enclosure and mechanicals – it’s a hard life for stage equipment. For the foot pedal input, [randy] is using a magnetic position sensor, but there’s no word if he’ll be using a fancy die-cast enclosure or a plastic injection molded unit.

The 2015 Hackaday Prize is sponsored by:

Improving A Cheap Guitar Pedal

pedul

If something doesn’t suit your needs, just change it. That’s a motto we live by, and it looks like [Doug] took up the same creed when he modified a cheap effects pedal.

The victim of [Doug]’s soldering iron is a Danelectro BLT Slap Echo – a tiny, cheap pedal in Danelectro’s mini ‘food named’ pedal series. Stock, this pedal’s slap back echo is set to a fixed amount of time. [Doug]’s mod changes that.

The mod consists of desoldering a single SMD resistor and replacing that with a 50k pot [Doug] had lying around. After mounting the pot between the two stock knobs, the new and improved pedal had a variable length echo. There are a few more mods possible with this pedal – changing some of the resistors on the filter for a better sound, or even connecting the rate pot to a wah-style rocker pedal for some wobbly Echoplex or Space Echo action.

You can check out [Doug]’s gallery of pics here.

An EQ Display For A Pedal Board

EQ

There are a lot of tinkerers out there who got their start in electronics with musical hacks. Surprisingly though, we don’t see many submissions to our tip line covering boost circuits for electric basses, rewiring guitar electronics, or even more complex effect pedals. [Deadbird], though, is bucking that trend with an EQ display stomp box that fits neatly on his pedal board.

[Deadbird]’s build isn’t a graphic equalizer that can change the volume of different frequency bands; instead, he used the MSGEQ7 chip to listen in on the signal his guitar is producing and display that on a 128×64 graphic backlit display.

The entire project was prototyped on a breadboard with an Arduino. After he got all the components working – a momentary switch to turn the pedal on and off, 1/4″ jacks for the input and output, and a power supply – [Deadbird] took an Arduino prototyping shield and made everything more permanent. Now he’s got an attractive pedal on his board that shows the signal coming from his guitar in seven neat bands.

Crank Out The Jams With [Dino]’s Fuzz Face

Weekly Hack a Day feature [Dino] is back again, this time with his very own guitar pedal. It’s modeled on a three-transistor Fuzz Face clone and sounds very good in our humble opinion.

Fuzz pedals were some of the first guitar pedals on the market, and for good reason. Their easy construction and simple theory of operation (just amplify sound until the transistor saturates) made them an economical and available pedal for the legends of rock in the 60s. [Dino]’s build follows this tradition of simplicity with a common 2N3904 transistor and a pair of BC547 Silicon transistors. We’re guessing [Dino] couldn’t find any cred-worthy and mojo-giving Germanium transistors, but the result sounds just as good as we could imagine.

To test out his pedal, [Dino] hooked up a [Jack White] style single string lap steel and turned everything up to 12*. The result is rock. Check out the build vid after the break.

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