Retrotechtacular: The Hammond Novachord

Just when we thought we’d heard of all the cool early synthesizers, a tipster rattled our jar with news that someone completely restored a Novachord. These spinet piano-shaped prototypical synthesizers were made by Hammond for only four years. About a thousand of them were built before sales sagged and parts became scarce in 1942. It is estimated that only 200 or so are still around today.

The Novachord’s sounds are generated by a bank of twelve monostable vacuum tube oscillators. Each one is tuned to a pitch of the chromatic scale in what is called divide-down architecture. [Hammond] and his co-creators [John Hanert] and [C.N. Williams] used the property of dividing a frequency in half to generate the same tone, but one octave lower. This design means that all 72 notes can be played at the same time. Adjustable formant filters shape the often otherworldly sounds, which are then passed through flexible tube-based envelopes.

[Phil] knew it would be a big job to restore a Novachord in any condition. Thousands of passive components all had to be replaced. The cabinet bore all the hallmarks of a well-used parlor instrument—water rings from cocktails, scratches, and cigarette burns galore. [Phil] says that woodworking really isn’t his thing, but he did an outstanding job nonetheless of sanding every nook and cranny and applying several coats of stain. There are tons of drool-inducing pictures on his project site, and several clips of [Phil] really putting it through its paces.

Thanks for the tip, [Mike]!

Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.

Retrotechtacular: The Trautonium Was Elemental to Electronic Music

Electrical engineer and music enthusiast [Freidrich Trautwein] was dissatisfied. He believed that the equal tempered scale of the piano limited a player’s room for expression. And so in 1930, [Trautwein] and an accomplished pianist named [Oskar Sala] began work on an electro-mechanical instrument that would bring the glissando of the string section’s fretless fingerboards to the keyboard player. [Trautwein] called his creation the Trautonium.

Sound is produced in the instrument by sawtooth frequency generators. It is then passed through filters and manipulated by the resistive string-based manuals. Frequency and intonation are varied relative to the position of the player’s finger along a length of non-conductive string and to the amount of pressure applied. This resistive string is suspended above a conductive metal strip between a pair of posts. A small voltage is applied to the posts so that when the string touches the metal strip below, the player manipulates a voltage-controlled oscillator. A series of metal tongues, also non-conductive, hover above the string. These are placed at scale intervals and can be used like keys.

This early synthesizer is capable of producing many kinds of sounds, from crisp chirps to wet, slapping sounds and everything in between. In fact, all of the sound effects in Alfred Hitchcock’s thriller The Birds were produced on a modified Trautonium by the instrument’s one and only master, [Oskar Sala]. He went on to score hundreds of films by watching them with the Trautonium at his fingertips, recording and layering his compositions into an eerie wall of sound.

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Hackaday Links: July 19, 2015

Everybody needs an external USB drive at some time or another. If you’re looking for something with the nerd cred you so desperately need, build a 5 1/4″ half height external drive. That’s a mod to an old Quantum Bigfoot drive, and also serves as a pretty good teardown video for this piece of old tech.

The Woxun KG-UV2D and KG-UV3D are pretty good radios, but a lot of amateur radio operators have found these little handheld radios eventually wear out. The faulty part is always a 24C64 Flash chip, and [Shane] is here to show you the repair.

Last year there was a hackathon to build a breast pump that doesn’t suck in both the literal and figurative sense. The winner of the hackathon created a compression-based pump that is completely different from the traditional suction-based mechanism. Now they’re ready for clinical trials, and that means money. A lot of money. For that, they’re turning to Kickstarter.

What you really need is head mounted controls for Battlefield 4. According to [outgoingbot] it’s a hacked Dualshock 4 controller taped to a bike helmet. The helmet-mounted controller has a few leads going to another Dualshock 4 controller with analog sticks. This video starts off by showing the setup.

[Jan] built a modeling MIDI synth around a tiny 8-pin ARM microcontroller.  Despite the low part count, it sounds pretty good. Now he’s turned his attention to the Arduino. This is a much harder programming problem, but it’s still possible to build a good synth with no DAC or PWM.

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!

An Electronic Woodwind With An Onboard Synthesizer

About a year ago, we saw a project on 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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Logic Noise: Sequencing in Silicon

In this session of Logic Noise, we’ll combine a bunch of the modules we’ve made so far into an autonomous machine noise box. OK, at least we’ll start to sequence some of these sounds.

A sequencer is at the heart of any drum box and the centerpiece of any “serious” modular synthesizer. Why? Because you just can’t tweak all those knobs and play notes and dance around at the same time. Or at least we can’t. So you gotta automate. Previously we did it with switches. This time we do it with logic pulses.

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Logic Noise: Sawing Away with Analog Waveforms

Today we’ll take a journey into less noisy noise, and leave behind the comfortable digital world that we’ve been living in. The payoff? Smoother sounds, because today we start our trip into analog.

If you remember back to our first session when I was explaining how the basic oscillator loads and unloads a capacitor, triggering the output high or low when it crosses two different thresholds. At the time, we pointed out that there was a triangle waveform being generated, but that you’d have a hard time amplifying it without buffering. Today we buffer, and get that triangle wave out to our amplifiers.


But as long as we’re amplifying, we might as well overdrive the amps and head off to the land of distortion. We’ll do just that and build up a triangle-wave oscillator that can morph into a square wave, passing through a rounded-over kinda square wave along the way. The triangle sounds nice and mellow, and the square wave sounds bright and noisy. (You should be used to them by now…) And we get everything in between.

And while we’re at it, we might as well turn the triangle wave into a sawtooth for that nice buzzy-bass sound. Then we can turn the fat sawtooth into a much brighter sounding pulse wave, a near cousin of the square wave above.

What’s making all this work for us? Some dead-boring amplification with negative feedback, and the (mis-)use of a logic chip to get it. After the break I’ll introduce our Chip of the Day: the 4069UB.

If you somehow missed them, here are the first three installments of Logic Noise:

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