Lo-Fi Tchaikovsky

February 22, 2023 by Chris Lott 4 Comments

[Kevin] over at Simple DIY ElectroMusic Projects recently upgraded his Lo-Fi Orchestra. To celebrate his 400th blog post, he programmed it to play Tchaikovsky’s 1812 Overture. Two Arduino Nanos, four Arduino Unos, four Raspberry Pi Picos, and one Raspberry Pi have joined the Lo-Fi Orchestra this year, conducted by a new Pico MIDI Splitter. Changes were made in every section of the orchestra except percussion. We are delighted that the Pringles tom and plastic tub bass drums remain, not to mention the usual assortment of cheap mixers, amps, and speakers.

Tchaikovsky’s score famously calls for some “instruments” not found in the typical orchestra — a battery of cannon and a carillon, for example. Therefore [Kevin] had to supplement the Lo-Fi Orchestra for this performance with extras — a JQ6500 MP3 module on clash cymbals, a bare metal MiniDexed Raspberry Pi playing the carillon, and a MCP4725 with a Lots-of-LEDs shield firing off cannon and fireworks, respectively.

Although slightly disappointed that the MCP4725 beat out Mr. Fireworks in the auditions, we do like the result. [Kevin] reports that the latest version is much more reliable and predictable, having eliminated various MIDI faults and electrical noise. It presents a stable platform for future musical presentations, a kind of on-demand Lo-Fi Orchestra jukebox, as he describes it. A detailed review of all the changes can be found in his explanatory blog post. Check out an earlier performance of Holst’s The Planets suite from our coverage back in 2021.

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A Better Playlist Shuffle Algorithm Is Possible

February 19, 2023 by Lewin Day 52 Comments

When listening to music, most of us reach for the shuffle button on the regular. This is then followed by a bunch of frustrating skips as we hear the same four or five tracks that have been regularly replayed for the last few days. [Ron Miller] wants to fix unsatisfying shuffles, and he’s developed the Miller Shuffle algorithm to do so.

[Ron] realized that many big name streaming services use incredibly simple algorithms to choose shuffled songs. This can often be as simple as songIndex=random(NumOfSongs). The problem with this is that even with a good random number source, you’ll get a lot of premature repetitions. If your music service doesn’t keep track of your shuffle-point between sessions, you’ll often get annoying repeats if you’re listening on a day-to-day basis.

To fix this, the Miller Shuffle algorithm aims to offer good randomness and no repeats without the excess resource usage of the commonly-cited Fisher-Yates algorithm. [Ron] explains it like this: “The way the algorithm works its magic is by utilizing multiple computations which are ‘symmetrical’, in that the range of values which go in are the same values which come out albeit in a different order.” Since its a deterministic fixed list, there’s no need to keep track of what songs have already been played to avoid repeats. Instead, the player must simply step through the index in order, one track after another. As long as a referenced index point is maintained, along with an ID of the shuffle order being used, no repeats should come up.

If you’re implementing a shuffle algorithm for your own music, you might want to give [Ron’s] work a look. He’s taken into account details like resource usage and small and large list sizes, to account for implementation issues for even very large streaming services. If you’re more interested in shuffling cards than songs, though, we can help there too!

How To Build Jenny’s Budget Mixing Desk

February 15, 2023 by Jonathan Bennett 35 Comments

Jenny did an Ask Hackaday article earlier this month, all about the quest for a cheap computer-based audio mixer. The first attempt didn’t go so well, with a problem that many of us are familiar with: Linux applications really doesn’t like using multiple audio devices at the same time. Jenny ran into this issue, and didn’t come across a way to merge the soundcards in a single application.

I’ve fought this problem for a while, probably 10 years now. My first collision with this was an attempt to record a piano with three mics, using a couple different USB pre-amps. And of course, just like Jenny, I was quickly frustrated by the problem that my recording software would only see one interface at a time. The easy solution is to buy an interface with more channels. The Tascam US-4x4HR is a great four channel input/output audio interface, and the Behringer U-PHORIA line goes all the way up to eight mic pre-amps, expandable to 16 with a second DAC that can send audio over ADAT. But those are semi-pro interfaces, with price tags to match.

But what about Jenny’s idea, of cobbling multiple super cheap interfaces together? Well yes, that’s possible too. I’ll show you how, but first, let’s talk about how we’re going to control this software mixer monster. Yes, you can just use a mouse or keyboard, but the challenge was to build a mixing desk, and to me, that means physical faders and mute buttons. Now, there are pre-built solutions, with the Behringer X-touch being a popular solution. But again, we’re way above the price-point Jenny set for this problem. So, let’s do what we do best here at Hackaday, and build our own. Continue reading “How To Build Jenny’s Budget Mixing Desk” →

An Open Hardware Eurorack Compatible Audio FPGA Front End

February 13, 2023 by Dave Rowntree 4 Comments

[Sebastian Holzapfel] has designed an audio frontend (eurorack-pmod) for FPGA-based audio applications, which is designed to fit into a standard Eurorack enclosure. The project, released under CERN Open-Hardware License V2, is designed in KiCAD using the AK4619VN four-channel audio codec by Asahi Kasei microdevices. (And guess what folks, there’s plenty of those in stock!) Continue reading “An Open Hardware Eurorack Compatible Audio FPGA Front End” →

Building A Plasma Piano Ain’t Easy

February 8, 2023 by Lewin Day 17 Comments

Electronic arcs can be made to “sing” if you simply modulate them on and off at audible frequencies. We’ve seen it done with single Tesla coils, and even small Tesla choirs, but [Mattias Krantz] took this to extremes by building an entire “plasma piano” using this very technique.

The build relies on ten transformers more typically used in cathode ray tubes. The transformers are capable of generating high enough voltages to create arcs in the air. The transformers are controlled by an Arduino, which modulates the arcs at musical frequencies corresponding to the keys pressed on the piano. Sensing the keys of the piano is achieved with a QRS optical sensor strip designed for performance capture from conventional pianos. For the peak aesthetic, the transformer outputs are connected to the metal hammers of the piano, and the arcs ground out on a metal plate in the back of the piano’s body. This lets arcs fly across the piano’s whole width as its played. Ten transformers are used to enable polyphony, so the piano to play multiple tones at once.

Building the piano was no mean feat for [Mattias], who admitted to having very limited experience with electronics before beginning the build. However, he persevered and got it working, while thankfully avoiding injury from high voltage in the process. This wasn’t easy, as Arduinos would regularly freeze from the noise produced by the arcs and the system would lose all control. However, with some smart software tweaks to the arc control and some insulating panels, [Mattias] was able to get the piano playable quite well with a beautiful chiptune tone.

It bears stating that HV work can be dangerous, and you shouldn’t try it at home without the proper understanding of how to do so safely. If you’re confident though, we’ve featured some great projects in this space before. Video after the break.

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Build A Circuit Sculpture-Style VU Meter For Music

February 2, 2023 by Lewin Day 19 Comments

One of the coolest things any sound system can have is some kind of musical visualization. Thumping level meters that pump with the volume are a great example, and were particularly popular in the 1980s. Now, you can build a rainbow set with great response, thanks to this guide from [Invexlab World].

The build relies on a very simple circuit that relies entirely on analog electronics in lieu of the usual digital signal analysis usually employed for the job. It’s a barebones design that’s assembled using a jig to create the attractive circuit sculpture structure. It uses simple colored LEDs, assembled in a line with red at the bottom, stepping through yellow and green, to blue and white at the top. A series of diodes is placed in series, with the sound level having to exceed the voltage drop of successive diodes to light the higher LEDs. It’s intended to be directly connected to a speaker’s audio input, and thus likely does load down the amplifier output slightly.

The result is an attractive rainbow VU meter display that would look great as a part of any old-school stereo setup. We can imagine it would look even better if it was cast in clear resin. Video after the break.

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1000 Aluminium Cans Cast Into A Guitar

January 30, 2023 by Lewin Day 31 Comments

Aluminium cans are all around us, and are one of readily recyclable. While you can turn them into more cans, [Burls Art] had other ideas. Instead, he turned roughly 1000 cans into a custom aluminium guitar.

Both the body and neck of the electric guitar are made out of aluminium. It’s an impressive effort, as manufacturing a usable neck requires care to end up with something actually playable when you’re done with it.

Producing the guitar started with a big propane furnace to melt all the cans down so they could be cast into parts for the guitar. 38 lbs of cans went into the project, and were first dried out before being placed into the furnace for safety reasons. Aluminium cans aren’t made of the best alloy for casting, but you can use them in a pinch. The cans were first melted down and formed into ingots to be later used for producing the neck and body.

[Burls Art] then built sand casting molds for his parts with a material called Petrobond. Wood plugs were used to form the sand into the desired shape. The neck casting came out remarkably well, and was finished with a grinder, hacksaw, and sandpaper to get it to the right shape and install the frets. The body proved more difficult, with its multiple cavities, but it came together after a second attempt at casting.

Fully kitted out with pickups and hardware, the finished product looks great, and weighs 12.3 pounds. It sounds remarkably like a regular electric guitar, too. It does pick up fingerprints easily, and does have some voids in the casting, but overall, it’s a solid effort for an all-cast guitar.

We’ve seen some other great casting projects over the years before, too. Video after the break.

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