Hackaday Podcast 066: The Audio Overdub Episode; Tape Loop Scratcher, Typewriter Simulator, And Relay Adder

Hackaday editors Elliot Williams and Mike Szczys stomp through a forest full of highly evolved hardware hacks. This week seems particularly plump with audio-related projects, like the thwack-tackular soldenoid typewriter simulator. But it’s the tape-loop scratcher that steals our hearts; an instrument that’s kind of two-turntables-and-a-microphone meets melloman. We hear the clicks of 10-bit numbers falling into place in a delightful adder, and follow it up with the beeps and sweeps of a smartphone-based metal detector.

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DJ Scratches Out Club Music With Tape, Not Turntables

It goes without saying that not everyone has the same taste in music, and what sounds amazing to one person will be the next person’s noise. But even if you’re not into hip-hop and the whole DJ scene, it’s hard not to be impressed with what [Jeremy Bell] has done here with his homemade tape loop “scratching” rig.

Most people have probably seen a DJ in a club using dual turntables to scratch or “scrub” a vinyl record back and forth to create effects that add to the music. Part musician and part performance artist, DJs and “turntablists” tend to be real crowd-pleasers. [Jeremy]’s “ScrubBoard” uses a loop of 2″ audiotape, the kind recording studios once used for multitrack recordings. The loop is driven across a wide platen by a motor with a foot pedal control, which he can use to quickly reverse the direction of travel and control the speed of the tape. A pair of playback heads are wired into the amplifier and can be positioned anywhere on the sometimes moving, sometimes stationary tape. The sounds he can create are rhythmic, percussive, and at times frenetic, but they’re always interesting. Check it out in action in the video below.

This version of the ScrubBoard is far from the first [Jeremy] has built. You may recall his first prototype from our coverage in 2014; that one used just a few feet of 1/4″ tape fixed to a board. He was still able to get some great sounds from it, but this version should really change things for him. 

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Guitar Effect Built From An Old Record Player

With little more than a gutted record player, a light bulb, and the legendary 555 timer IC, [Jacob Ellzey] has constructed this very slick optical tremolo effect for his guitar. By modulating the volume of the input signal, the device creates the wavering effect demonstrated in the video after the break.

The key is a vinyl record with large tabs cut out of it. As the record spins, these voids alternately block and unblock a small incandescent bulb. A common GL5537 photoresistor, mounted on the arm that originally held the player’s needle, picks up the varying light levels and passes that on to the electronics underneath the deck. An important note here is that different spacing and sizing of the cutouts will change the sound produced by the effect. [Jacob] has already produced a few different designs and plans on experimenting with more now that the electronics are completed.

Under the hood there’s a voltage divider and low gain amplifier connected to the photoresistor, and also a 555 timer circuit that’s driving the incandescent bulb. Once he was done fiddling with them, the circuit was moved to a neat little protoboard. A pair of potentiometers mounted through the side of the record player allow for adjusting the depth of the effect itself, as well as the output volume. Naturally, there’s also an external foot pedal that allows keying the effect on and off without taking your hands from the guitar.

As is usually the case, everything was going well on this project until the final moments, when [Jacob] found that the circuit and bulb were both browning out when powered from the same transformer. As a quick fix, he gutted a Keurig and used its transformer to drive the light bulb by itself. With independent power supplies, he was ready to rock.

Of course this isn’t the first time we’ve seen a piece of consumer electronics modified into a guitar effect, but if you’re looking for something a bit more built for purpose, there’s plenty of high-tech options to keep you busy.

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Turntable Spins Color And Sound Together

If you can’t grow your own synesthesia, buying electronics to do it for you is fine. Such is the case with the CHROMATIC by [Xavier Gazon], an artist who turns all kinds of electronics into circuit-bent musical art pieces. His project turns an old Philips Music 5120 turntable into a colorful MIDI sequencer, inspired by older 20th century instruments such as the Optophonic Piano and the Luminaphone.

The CHROMATIC uses colored pucks placed on a converted turntable to perform a looping sequence of chords in a given musical scale, generating MIDI data as output. Where its inspirations used primitive optics as their medium, this project employs a Teensy microcontroller and two modern optical sensors to do the work. One of these is a simple infrared sensor which tracks a white spot on the edge of the turntable, generating a MIDI clock signal to keep everything quantized and in sync. The other is a color sensor mounted on the tone arm, which can tell what color it sees and the height of the arm from the turntable.

While the instrument is still in beta testing phase details on how notes are generated aren’t yet given, though the general idea is that they are dictated by the color the tone arm sees and its position above the platter. Moving the tone arm changes which pucks it tracks, and the speed of the turntable can also be adjusted, changing how the melody sounds.​

The CHROMATIC is a very interesting project, but it’s not the first optical-based turntable hack we’ve seen here. We’ve also seen a much weirder use for a color sensor, too. Check out the video of this one in action after the break.

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Printed It: Hand Cranked Photography Turntable

Even a relatively low-end desktop 3D printer will have no problems running off custom enclosures or parts for your latest project, and for many, that’s more than worth the cost of admission. But if you’re willing to put in the time and effort to become proficient with necessary CAD tools, even a basic 3D printer is capable of producing complex gadgets and mechanisms which would be extremely time consuming or difficult to produce with traditional manufacturing techniques.

Printable bearing cross-section

Once you find yourself at this stage of your 3D printing career, there’s something of a fork in the road. The most common path is to design parts which are printed and then assembled with glue or standard fasteners. This is certainly the easiest way forward, and lets you use printed parts in a way that’s very familiar. It can also be advantageous if you’re looking to meld your own printed parts with existing hardware.

The other option is to fully embrace the unique capabilities of 3D printing. Forget about nuts and bolts, and instead design assemblies which snap-fit together. Start using more organic shapes and curves. Understand that objects are no longer limited to simple solids, and can have their own complex internal geometries. Does a hinge really need to be two separate pieces linked with a pin, or could you achieve the desired action by capturing one printed part inside of another?

If you’re willing to take this path less traveled, you may one day find yourself creating designs such as this fully 3D printed turntable by Brian Brocken. Intended for photographing or 3D scanning small objects without breaking the bank, the design doesn’t use ball bearings, screws, or even glue. Every single component is printed and fits together with either friction or integrated locking features. This is a functional device that can be printed and put to use anywhere, at any time. You could print one of these on the International Space Station and not have to wait on an order from McMaster-Carr to finish it.

With such a clever design, I couldn’t help but take a closer look at how it works, how it prints, and perhaps even some ways it could be adapted or refined going forward.

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A Scratch Instrument For Ants

If you think that this scratch instrument looks as though it should be at least… three times larger in order to be useful, you’d be wrong. This mighty pocket-sized instrument can really get the club hopping despite its diminuitive size. Despite that, the quality of the build as well as its use of off-the-shelf components for almost every part means that if you need a small, portable turntable there’s finally one you can build on your own.

[rasteri] built the SC1000 digital scratch instrument as a member of the portabilist scene, focusing on downsizing the equipment needed for a proper DJ setup. This instrument uses as Olimex A13-SOM-256 system-on-module, an ARM microprocessor, and can use a USB stick in order to load beats to the system. The scratch wheel itself uses a magnetic rotary encoder to sense position, and the slider is miniaturized as well.

If you want to learn to scratch good and learn to do other things good too, there’s a demo below showing a demonstration of the instrument, as well as a how-to video on the project page. All of the build files and software are open-source, so it won’t be too difficult to get one for yourself as long as you have some experience printing PCBs. If you need the rest of the equipment for a DJ booth, of course that’s also something you can build.

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Automated Turntable For 3D Scanning

Those just starting out in 3D printing often believe that their next major purchase after the printer will be a 3D scanner. If you’re going to get something that can print a three dimensional model, why not get something that can create said models from real-world objects? But the reality is that only a small percentage ever follow through with buying the scanner; primarily because they are notoriously expensive, but also because the scanned models often require a lot of cleanup work to be usable anyway.

While this project by [Travis Antoniello] won’t make it any easier to utilize scanned 3D models, it definitely makes them cheaper to acquire. So at least that’s half the battle. Consisting primarily of a stepper motor, an Arduino, and a EasyDriver controller, this is a project you might be able to assemble from the parts bin. Assuming you’ve got a pretty decent camera in there, anyway…

The general idea is to place a platform on the stepper motor, and have the Arduino rotate it 10 degrees at a time in front of a camera on a tripod. The camera is triggered by an IR LED on one of the Arduino’s digital pins, so that it takes a picture each time the platform rotates. There are configurable values to give the object time to settle down after rotation, and a delay to give the camera time to take the picture and get ready for the next one.

Once all the pictures have been taken, they are loaded into special software to perform what’s known as photogrammetry. By compiling all of the images together, the software is able to generate a fairly accurate 3D image. It might not have the resolution to make a 1:1 copy of a broken part, but it can help shave some modeling time when working with complex objects.

We’ve previously covered the use of photogrammetry to design 3D printed accessories, as well as a slightly different take on an automated turntable a few years ago. The process is still not too common, but the barriers to giving it a try on your own are at least getting lower.

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