Busted Wah Pedal Becomes New Synth Tool

Sometimes we get lucky and find a part we need for a project in our parts drawer. [Scissorfeind] got even luckier and found a part for his project lying around in the street. It was a Crybaby Wah pedal, a classic effects pedal typically used for a guitar. Since it was somewhat damaged, [Scissorfeind] got to work creating a control voltage (CV) and volume circuit for his Korg synthesizer.

For those who aren’t synthesizer aficionados, CV is a method of controlling the pitch of a tone. A higher voltage creates a higher tone and vice-versa. The wah pedal has a rocker on it that allows one’s foot to control the effect, but this particular one has been modified for CV instead of the wah-wah sound these pedals normally make. [Scissorfeind] built in a switch that will allow it to control volume as well, which makes this pedal quite unique in the effects world.

[Scissorfeind] built the custom circuit out of other parts he had lying around (presumably not in the street) and put the entire thing together on perfboard, then fit it all back together in the pedal. Now he has a great control voltage pedal for the vintage Korg synthesizer he recently restored! [Scissorfeind] knows his way around a synth, but if you’re looking to get started on a synthesizer project we have a great tutorial for you!

Headphone Amp Features A Tiny CRT

[ErikaFluff] needed an amp for his Grado open cans. Rather than build yet another boring black box, he built what may be the most awesome headphone amp ever. [ErikaFluff] added a tiny CRT to the project, which displays the current audio waveform passing through the amp. He packaged all this up in a customized Hammond box which makes it look like it just rolled off the line from some audiophile studio.

The amplifier in this case is based upon the CMoy, a common headphone amp design. [ErikaFluff] added a MOSFET on the output to drive his relatively low impedance (32 ohm) Grado headphones with reasonable volume. The CRT is from an old video camera viewfinder. Before LCDs were advanced and cheap enough to include in video cameras, CRTs were the only show in town. These tiny black and white screens use high voltage to scan an electron beam across a phosphor screen just like their bigger brethren.

In action! - ImgurSince he was going with an oscilloscope style vector scan rather than the raster scan the screen electronics were originally designed for, [ErikaFluff] had to create his own horizontal and vertical deflection circuits. Horizontal scan is created by a 555 timer generating a sawtooth wave at 75 Hz. Vertical deflection is via an LM386 driving a hand wound impedance matching transformer. The high voltage flyback transformer and its associated driver circuit were kept from the original CRT, though repackaged to make them as small as possible.

You might think that having a few thousand volts next to a sensitive audio amplifier would cause some noise issues. We also worried a bit about shorts causing unexpected shock treatments through the wearer’s ears. [ErikaFluff] says there is no need to for concern. The signal is fed to the CRT circuit through optocouplers. The audio circuit is also electrically split from the CRT and runs on a virtual ground. Judicious amounts of shielding tape keeps the two circuits isolated.

This may not be the most practical project, but we think it’s pretty darn cool. The response over on Reddit’s electronics subreddit seems to be positive as well. We hope [ErikaFluff] is sitting down when this post gets published!

An Electronic Woodwind With An Onboard Synthesizer

About a year ago, we saw a project on Hackaday.io for a MIDI wind controller. Keyboard MIDI controllers are a dime a dozen, but if you want something that actually sounds like a brass or woodwind instrument, you need something that’s controlled by a breath sensor. Since then, this project has been updated with an onboard synthesizer. It sounds great, and thanks to some interesting components, the part count is actually really low.

The synthesizer used for this project is just a single chip – the DSP-G1 from [Jan Ostman]. This isn’t a custom ASIC or anything fancy; it’s just an 8-pin ARM microcontroller in DIP format, the LPC810.

The rest of the instrument is just a series of pressure sensors along the body, and a breath sensor. The plan is to stuff all the electronics – a microcontroller to read the touch and breath sensors, the DSP-G1 chip, and the battery  – inside the body of the instrument. That’s something that would be incredibly cool, and much more capable than the wind controllers that are available today.

You can see a few videos of the wind controller below.

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Vintage Stereo Reborn With All The Bells And Whistles

We always like seeing projects that salvage a classic piece of technology, and this one doesn’t disappoint. It’s a vintage kiosk- or console-style stereo, repurposed with every useful feature imaginable, but still made to look original. Until you open the lid, that is.

[Julian] has been hard at work on rebuilding this 1957 RCA stereo, and since he’s no stranger to these types of rebuilds, the results are pretty impressive. Underneath the hood is a 22″ touchscreen running Windows 7 and a Lepai amplifier. The controls for the stereo were placed towards the back, along with USB ports and an RJ45 connector for the computer.

The speakers in the stereo also needed to be replaced. For this, [Julian] used a set of Dayton speakers that worked well enough for this application. After mounting the speakers and all the other hardware in the unit, [Julian] noted that while it isn’t an audiophile’s dream stereo, it was nice to have all of these parts integrated together into something that looks nice. We’d have to agree!

There are a lot of rejuvenated antique stereos around too, like this Bluetooth-enabled tube amp radio, or this Soviet-era handheld, or even this slightly more modern stereo. There’s just something classy about having a vintage-looking thing spruced up with modern technology!

Microcassette Recorders Become A Tape Delay

Long before audio engineers had fancy digital delays, or even crappy analog delays, there were tape delays. Running a tape around in a loop with a record and play head is the basis of the Echoplex and Space Echo, and both of these machines are incredible pieces of engineering.

Microcassette recorders are not, in general, incredible pieces of engineering. They do, however, have a strip of magnetic tape, a record head, and a play head. Put two of them together, and you can build your own tape delay.

The basic principle of a tape delay is simple enough – just run a loop of tape round in a circle, through a record and playback head, record some audio, and send the output to an amplifier. In practice, it’s not that simple. [dogenigt] had to manufacture his own tape loop from microcassettes, a process that took far too long and was far too finicky.

For a control circuit, [dogenigt] is using four audio pots and one linear pot for speed control. The audio pots are responsible for input gain, feedback, the amplitude of the clean signal, and the output of the signal after it’s been run through the delay.

Apart from being one of those builds that’s very dependent on the mechanical skill of the builder, it’s a pretty simple delay unit, with all the electronics already designed for a stripboard layout. You can hear an example of what it sounds like below.

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SamplerBox Uses Raspberry Pi 2 to Make Music

[JosephErnest] wanted a cost-effective alternative to the commercially available MIDI samplers and expanders on the market. He also wanted to avoid being tethered to a computer all the time. His solution is the SamplerBox, a standalone drop-and-play sampler that costs less than 100 euros to make. Simply insert an SD card with your sample set in WAV format, boot it up, and play it through your keyboard or MIDI controller to your heart’s content!

[JosephErnest] used a Raspberry Pi 2 in the SamplerBox because it provided higher performance. He wasn’t thrilled with the sound quality of its built-in soundcard, so he installed a USB DAC PCM2704 (an older model, but any USB DAC will do) to output the audio. He also installed a USB card reader to make switching SD cards containing sampler sets easier while keeping the Pi 2’s own microUSB card exclusively for the OS and software. Both a DIN MIDI connector and USB are included as MIDI inputs in the design. If you only plan to use a USB, the MIDI connector can be omitted from the build. The software is written in Python and cython which allows the Pi 2 to have over 128-voice polyphony. Users can also create their own sample sets to use with the SamplerBox. Preset changes can be made on the fly. All we need to rock out are some music lessons!

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Bringing a Century Stereo into the 21st Century

Way back in the previous century, people used to use magnetized strips of tape to play music. It might be hard to believe in today’s digital world, but these “cassette” tapes were once all the rage. [Steve] aka [pinter75] recently found a Bang & Olufsen stereo with this exact type of antequated audio playback device, and decided to upgrade it with something a little more modern.

Once the unit arrived from eBay and got an electronic tune-up, [pinter75] grabbed a Galaxy S3 out of his parts drawer and got to work installing it in the old cassette deck location. He used a laser cutter to make a faceplate for the phone so it could be easily installed (and removed if he decides to put the tape deck back in the future).

The next step was wiring up power and soldering the audio output directly to the AUX pins on the stereo. Once everything was buttoned up [pinter75] found that everything worked perfectly, and mounted the stereo prominently on his wall. It’s always great when equipment like this is upgraded and repaired rather than thrown out.