Musical Hacks

1374 Articles

Upcycled Practice Amp Build Goes To Eleven

May 26, 2022 by 19 Comments

What do you call someone who gives the toddler in your life a musical instrument as a gift? In most cases, “mortal enemy” is the correct answer, but not everyone feels quite so curmudgeonly, and might even attempt to turn up the volume a bit. Such is the case with this wonderfully detailed practice amp for the grandkids’ electric ukelele.

The aptly named [packrat] [Professor Mayhem] really made this build a tour de force of scrap bin sourcing. The amp is built around a module salvaged from an old TV, a stereo Class-D amp that was modified to provide 30 watts output and a volume control. The driver came from a flood-damaged speaker unit, and the power supply from a gutted wall wart. The case was built with scrap plywood and covered with pebble-grain fabric to give it that pro audio look, while the chassis for the electronics was bent from a piece of sheet steel.

But it’s the tiny details that really sell this project. Everything from the pilot light to the pointer knob screams 1970s, as do the painstaking front panel lettering and vinyl “Monkeydyne” logo. [Professor Mayhem] even went the extra mile to create an etched-brass serial number plate, a mock specs and safety label, and even a QA inspection tag that was (sort of) stapled inside the cabinet.

We tip our hats to [Professor Mayhem] for this four-month labor of love and obvious nostalgia trip, which the kids are sure to love. [Professor Mayhem] does admit that some will argue with his decision to use a Class D amp and a switch-mode power supply, but let’s be real — for the application, it’s probably more than sufficient.

Thanks for the tip, [packrat].

Sound Generation Board Makes The Tunes

May 20, 2022 by 4 Comments

[Mcjack123] has been getting into chiptunes lately and realized that his original interest started in 2018 when he used an Arduino to turn a TI-84 calculator into a sound machine. His latest iteration is a custom-designed soundboard and he takes us through the design and construction of it in a recent post.

The work models classic sound generators like the 2A03 or the Commodore 64 SID. You have a bunch of simple waveform generators along with filters and modulators to make various effects. These boards eventually gave way to FM synthesis devices like the Yamaha OPL2 and OPL3 chips. All of these cards accepted commands and generated audio on their own. More modern boards are more likely to simply convert digital data from the computer into audio.

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MIDI Controller Looks Good, Enables Your Air Guitar Habit

May 18, 2022 by 8 Comments

We all want to be guitar heroes, but most of us have to settle for letting a MIDI board play our riffs using a MIDI controller. [Joris] thinks a MIDI controller should look like a cool instrument and thus the Ni28 was born. Honestly, we first thought we were looking at wall art, but on closer look, you can see the fretboard and the soundhole are festooned with buttons.

Actually, they aren’t really buttons. The Ni in the name is because the buttons are nickel-plated brass plates that act like touch switches. There’s virtually no activation force required and you can easily touch more than one plate at a time.

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Balloon Guitar Is An Absolute Gas, Helium Or Not

May 14, 2022 by 10 Comments

Guitars are most typically built out of wood. Whether it’s an acoustic guitar with a big open cavity, or a solid-body electric, there’s generally a whole lot of wood used in the construction. However, [Mattias Krantz] shows us that alternative construction methods are entirely possible, by building his own balloon guitar.

The balloon guitar still has a neck, bridge, and strings just like any other. However, in place of the resonant cavity of an acoustic guitar, there is provision to install a large balloon instead. It’s actually quite interesting to watch — with the balloon installed, the guitar delivers much more volume than when played without a resonant cavity at all.

The guitar was actually built to test if swapping out air in the balloon for helium would shift the pitch of the sound. Of course, a guitar’s pitch comes from the tension on the vibrating strings, so changing the gas in the resonant cavity doesn’t directly affect it. Instead, much like inhaling helium to affect the human voice, the change is to the timbre of the sound, not the fundamental pitch itself. It sounds as if the guitar has been given a subtle treble boost.

It’s a fun build, and one that shows us that it’s possible to build musical instruments in many ways, not just using traditional techniques. If you want to further play with your guitar’s sound, though, consider turning to the world of machine learning.

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MiniDisc Player Supports Full Data Transfer

May 14, 2022 by 28 Comments

Between the era of the CD and the eventual rise and domination of streaming music platforms, there was a limbo period of random MP3 players mixed in with the ubiquitous (and now officially discontinued) iPod. In certain areas, though, the digital music player of choice was the MiniDisc, a miniature re-writable CD player with some extra digital features. Among them was the ability to transfer music to the discs over USB, but they did not feature the ability to transfer the songs back to a computer. At least until now, thanks to this impressive hack from [asivery].

Although it sounds straightforward, this trick has a lot of moving parts that needed to come together just right. The MiniDisc player uses a proprietary encoding format called ATRAC, so a codec is needed for that. The MiniDisc player stores data from the disc in a 40-second buffer when playing, so the code reads the data directly from DRAM in 40-second chunks, moves the read head, repeats the process as needed, then stitches the 40-second parts back together. It can work on any Sony NetMD portable, if you are lucky enough to still have one around.

The project is a tremendous asset to the MiniDisc community, especially since the only way to recover data from a MiniDisc player prior to this was to use a specific version known as the RH-1. As [asivery] reports, used RH-1 players are going for incredibly high prices partially because of this feature. Since this new method demonstrates that it’s possible to do with other devices, perhaps its reign in the MiniDisc world will come to a close. For those still outside the loop on this esoteric piece of technology, take a look at this MiniDisc teardown.

Thanks to [Maarten] for the tip!

Big Audio Visualizer Pumps With The Music

May 13, 2022 by 2 Comments

A spectrum analyzer is a great way to create exciting visuals that pulse in time with music. [pyrograf] wanted a big one as a display piece, so set about whipping up something of their very own.

An ESP32 microcontroller serves as the heart of the build, with its high clock rate and dual cores making it a highly capable choice for the job. Audio from a microphone is amplified and pumped into the ESP32’s analog input. Core 0 on the ESP32 then runs a Fast Fourier Transform on the input audio in order to determine the energy in each frequency band. The results of this FFT are then passed to Core 1, which is used to calculate the required animations and pipe them out to a series of WS2812B LEDs.

Where this build really shines, though, is in the actual construction. Big chunks of acrylic serve as diffusers for the LEDs which light up each segment of the spectrum display. Combine the big pixel size with a nice smooth 30 Hz refresh rate on the LEDs, and the result is a rather large spectrum analyzer that really does look the business.

We’ve seen some similar builds over the years, too. Video after the break.

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How The Roland 808 Cowbell Worked

May 12, 2022 by 9 Comments

Every generation has an instrument which defines its sound, and for those whose formative musical years lie in the 1980s, a very strong contender to the crown is the Roland TR-808 percussion synthesizer. Its sounds can be recognized across a slew of hits from that era and every decade since, and though the original instrument wasn’t a commercial success it remains accessible through sample packs, emulations, and clones. The 808 was an all-analogue device that didn’t use samples, thus [Mark Longstaff-Tyrrell] has been able to reproduce its distinctive cowbell sound with reference to some of the original circuitry.

It shouldn’t come as too much of a surprise to find that the circuit is refreshingly simple. The trigger pulse is converted into an envelope which controls a pair of oscillators. The mixed output passes through a bandpass filter to create the distinctive sound on the output which you can hear in the video below the break. The circuit is recreated on a breadboard with the only concession to modernity being a microcontroller taking the place of the Schmitt trigger oscillators in the original.

Altogether it provides a fascinating insight into the synthesis behind a classic sound, and gives us an increased appreciation for the design skills of those Roland engineers who created it. We’ve looked at the 808 before a few times, including an explanation of the famous faulty transistors which contributed to its sound.

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