Open Source Synthesizers Hack Chat

Matt Bradshaw is a musician, maker, and programmer with a degree in physics and a love for making new musical instruments. You may remember his PolyMod modular digital synthesizer from the 2018 Hackaday Prize, where it made the semifinals of the Musical Instrument Challenge. PolyMod is a customizable, modular synthesizer that uses digital rather than analog circuitry. That seemingly simple change results in a powerful ability to create polyphonic patches, something that traditional analog modular synths have a hard time with.

Please join us for this Hack Chat, in which we’ll cover:

  • The hardware behind the PolyMod, and the design decisions that led Matt to an all-digital synth
  • The pros and cons of making music digitally
  • Where the PolyMod has gone since winning the Musical Instrument Challenge semifinals

You are, of course, encouraged to add your own questions to the discussion. You can do that by leaving a comment on the Open Source Synthesizers Hack Chat and we’ll put that in the queue for the Hack Chat.


Our Hack Chats are live community events on the Hack Chat group messaging. This week we’ll be sitting down on Wednesday, January 23, at noon, Pacific time. If time zones got you down, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on

You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about. And don’t forget to check out the Modular Synth Discussion, a very active chat that digs into the guts of all sorts of modular synthesizers.

Analog Clock Goes Digital, or Vice Versa

Designing a good clock takes a lot of considerations. It’s not just hands, faces, and numbers anymore; there are also word clocks, electronic clocks, marble clocks, or water clocks, and just about anything else imaginable can be used to tell time. Of course, electronic clocks are great for their versatility, and this one shows off an analog-looking clock that is (of course) digital, leveraging all of the perks of analog with all of the upsides of digital electronics.

One of the key design considerations that [Sasa] had while building this piece was that it needed to be silent. LEDs certainly fit that description, so the decision was made to go with an WS2812b ring. It runs using a STM ST32F103 Nucleo board (and a cheaper version of it in later versions of this clock) which shows a red LED for the current hour, yellow LEDs for the traditional analog clock divisions, a green LED for the current minute, and glows the rest of the LEDs up to the current minute with a rainbow pattern.

This is a really clean, simple build with good design at its core, and would be easy to replicate if you’re looking for an eye-catching clock to build. As a bonus, all of the schematics and code are available on the project site, so everything you need is there. If you’re looking for more inspiration, there are some clocks that are even more unique, like this marble clock that is a work of art — but is anything but silent.

7 Segment Clockwork Display Made From Cardboard

We’ve seen a variety of oddball 7-segment displays in the past, but this one uses a new material: both for the display and the mechanical mechanism that drives it; cardboard. Yup, the whole thing is made from cardboard, wood and a few rubber bands. [The Q] shows how he put together in this nice video, starting from first principles that show how the segments are made: simple pieces of cardboard painted on one side with fluorescent paint. A piece of wood pushes the element out to blank it, and each element is connected to a cam wheel that pushes the wood in or out.

The really clever bit is that [The Q] mapped digits 0 – 9 onto a matrix for which of the 7 segments is “on” or “off”. He then used this information to create a stack of 7 cams on a central axle. As you rotate the axle, the cams turn, moving the wooding arms. The arms then cause the elements to flip as they count up through the digits. In essence, he engineered a physical decimal to 7 segment decoder, much like the electronic one inside the SN74LS47. The whole assembly is capped by a knob that indicates which digit is currently displayed. If mechanical displays like this are your thing, check out this one made from LEGO parts, or this awesome 3D printed creation.

Continue reading “7 Segment Clockwork Display Made From Cardboard”

Books You Should Read: Designing Reality

These days, budget CNC builds are mainstream. Homebrew 3D printers and even laser cutters are old hats. Now I find myself constantly asking: “where’s it all going?” In the book, Designing Reality, Prof Neil Gershenfeld and his two brothers, Alan and Joel, team up to answer that question. In 250 pages, they forecast a future where digital fabrication tools become accessible to everyone on the planet, a planet where people now thrive in networked communities focused on learning and making.

Designing Reality asks us to look forward to the next implications of the word “digital”. On its surface, digital  means discretized, but the implications for this property are extreme. How extreme? Imagine a time where cnc-based fabrication tools are as common as laptops, where fab labs and hackerspaces are as accepted as libraries, and where cities are self-sufficient. The Gershenfelds invite us to open our eyes into a time where digital has vastly reshaped our world and will only continue to do so. Continue reading “Books You Should Read: Designing Reality”

Old LED Light Bulbs Give Up Filaments for Spider Web Clock

We love it when something common gets put to a new and unusual use, especially when it’s one of those, “Why didn’t I think of that?” situations. This digital clock with a suspended display is just such a thing.

The common items in this case were “filaments” from LED light bulbs, those meant to mimic the look of clear-glass incandescent light bulbs. [Andypugh] had been looking at them with interest for a while, and realized they were perfect as the segments for a large digital clock. The frame of the clock was formed from bent brass U-channel and mounted to an oak base via turned stanchions. The seven-segment displays were laid out in the frame and the common anodes of the LED filaments were connected together, with the cathode for each connected to a very fine wire. Each wire was directed through a random hole in the frame and channeled down into the base, to be hooked to one of the four DS8880 VFD driver chips. The anode wires form a lacy filigree behind the segments, which catch the light and make then look a little like a spider’s web. It looks great, but nicht für der gefingerpoken – the frame is at 80 VDC to drive the LED segments. The clock is synced to the UK atomic clock with a 60-kHz radio link; see the long, painful sync process in the video below.

We like the open frame look, which we’ve seen before with an equally dangerous sculptural nixie clock. And this gives us some ideas for what to do with those filament LEDs other than turning them back into a light bulb. And if [Andy] sounds familiar, it could be because he’s appeared here before. First of all resurrecting the parts bin for an entire classic motorcycle marque, and then as the designer of SMIDSY, a robot competitor in the first incarnation of the UK Robot Wars series.

Continue reading “Old LED Light Bulbs Give Up Filaments for Spider Web Clock”

Digital Kiln

A kiln or foundry is too often seen as a piece of equipment which is only available if a hackspace is lucky enough to have one or individuals are dedicated enough to drop the cash for one of their own. [The Thought Emporium] thought that way until he sourced materials to make his own kiln which can also be seen after the break. It costs half the price of a commercial model not including a failed—and exploded—paint can version.

As described in the video, these furnaces are tools capable of more than just pottery and soft metal baubles. Sure, a clay chess set would be cool but what about carbon fiber, graphene, aerogel, and glass? Some pretty hot science happens at high temperatures.

We get a nice walk-through of each part of the furnace starting with the container, an eleven-gallon metal tub which should set the bar for the level of kiln being built. Some of the hardware arrangements could be tweaked for safety and we insist that any current-carrying screw is safely mounted inside an enclosure which can’t be opened without tools. There’s good advice about grounding the container if metal is used. The explanation of PID loops can be ignored.

What else can you do with a kiln? How about jewelry, heat treating metal, or recycle your beer cans into an engine.

Continue reading “Digital Kiln”

Friday Hack Chat: Reverse Engineering the Digital Compact Cassette

For this week’s Hack Chat, we’re talking about reverse engineering the Digital Compact Cassette. Why should we care about an obsolete format that was only on the market for four years?  Because if a copy of the Spin Doctor’s Pocket Full of Kryptonite costs $50 USD on the used market, it has to be good.

In the early 1990s, several different digital magnetic tape formats came onto the scene. The MiniDisc was magneto-optical, yes, but back in the day it was amazing for recording bootlegs. DAT also appeared in the early 90s, and it was a godsend for recording studios. There was another format introduced in 1992, the Digital Compact Cassette. It was backward compatible with standard audio cassettes, an important feature, because no one would want to replace their entire cassette-based music collection with a new-fangled digital format. That would be just lunacy.

Our guest for this week’s Hack Chat will be [Jac Goudsmit], prolific creator on, with projects ranging from the L-Star Software Defined 6502 Computer to a GPS Controlled FischerTechnik Clock. [Jac] grew up on a PET 2001, and in the years since he’s worked on projects ranging from motion control systems for lithography equipment, pick and place machines, and even at a Radio Shack. In this Hack Chat, he’ll be discussing the history of the Digital Compact Cassette, the behind the scenes on how stereo PCM is recorded to tape, and other topics like the difference between CS/EE careers in the Netherlands and the USA.

join-hack-chatOur Hack Chats are live community events on the Hack Chat group messaging. Our Hack Chats usually happen on Fridays at Noon, so buckle up because this is going down Friday, December 1, at 12:00 PST. What time is that where you live? Who cares! Here’s a time zone converter!

Click that speech bubble to the left, and you’ll be taken directly to the Hack Chat group on

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.