Introducing Sprockit Mini-Synth

Sprockit Mini-Synth

Rockit’s getting a little brother, Sprockit. My goal with Sprockit it to take a lot of Rockit goodness and compress it down to something smaller and a bit cheaper. I’m achieving both goals by having a very dense design and by reducing some of the features. Sprockit is 4″x4″ versus Rockit’s 5.1″x8.6″, so it’s substantially smaller, like pocket sized (I would’ve called it Pockit Rockit, but there are some products out there already). There are obviously fewer knobs, LEDs, and switches. All of the control parameters are still there though and will be accessible via an external MIDI controller. The microcontroller is downsized from an ATMEGA644 to an ATMEGA328. I’m also incorporating a lot of the things that I’ve learned from doing Rockit and rolling those improvements into Sprockit. This image is my first prototype and I’m well into prototype two, which will be much improved. I’ll be doing a workshop with Dorkbot Chicago at the end of February where people can build Sprockit with me. I’ll probably do another Kickstarter project after that. I’ve learned from Rockit that I’ll need to get the case designed before I release it though. Click through for a complete feature rundown.Continue reading

The Final Board: Hackme Rockit 8 Bit Synth

The Final PCB - All Parts in Their Places

Here’s a picture of the final board. I’m closing in on the end.  I’m finalizing the implementation of the looping feature, which massively expands the capabilities of this little 8 Bit Synth. Once I’m satisfied with that, I’ll be shooting a video of the Rockit in action.  The video will be part of my project on Kickstarter.  Once it’s up, I’ll be officially taking pre-orders.  I’ve done some value tweaks in the last few days and boy, oh boy, is it sounding sweet!

Rockit 8 Bit Synth: Final Schematic and PCB

The Rockit 8 Bit Synth Schematic

I have ordered what I’m hoping will be the final PCB.  I’ve learned over the years that you never really know what you’ll discover once you build one up and hold it in your hands, but I’m very hopeful. I had to do this layout mostly to fix a few things. The schematic really hasn’t changed much in the last couple months.  Some values were adjusted but I like where things are right now in the hardware. 

From here on, it’s all software.  I’m working on developing more complex and interesting oscillator waveshapes, like morphing waveshapes and enveloped blended waveshapes.  They sound pretty cool.  I’ve also decided to add a last minute feature.  A lot of my friends have commented that they don’t necessarily have a MIDI controller but they’d like to buy one, so I’m adding a feature to make the unit kind of standalone.  I’m calling this a drone/loop feature.  Basically, I’m going to add a small sequencer. I’m not exactly sure how it will all work, but it should turn out pretty cool in the end since the Rockit makes pretty nifty droning sounds especially when you get the filter and the LFOs involved.  I was messing with this feature last night and I accidentally found an arpeggiation mode when the LFO is set to trigger the oscillator detune.  It sounded awesome, especially with some of the quirky new waveshapes I’ve added to the LFO.   Other than these new features, I’ll be fine tuning the software to get it ready for release.  I’ll be posting this project on Kickstarter after the new pcb comes in and I make a little video.  I’ve got some surprises for that, so stay tuned.  Here’s an image of the final PCB.

The Rockit 8 Bit Synth PCB

Rockit 8 Bit Synth: The Final Stretch

Rockit Silkscreen - Parts and Locations

I am so excited to announce that I am almost done. The hardware has been finalized. The circuit and all the values are a wrap. Everything is working: MIDI, filters, synthesis, LFOs, envelopes, Voltage-Controlled Amplifier, LEDs, buttons, patch save and recall… I’ve got the first pass of the pcb finished as shown in the silkscreen image above. I’ve gotten to the final knob locations and am pretty happy with that.  It’s been a journey but the final design should be on sale within the next couple months.  I’m looking at options for selling it from licensing it to doing it myself.  I might put up a project on Kickstarter. Stay tuned on that front. 

Things I still have to get done are mostly software tasks:  finalize pitch bend implementation, test filter audio in, flush out and finalize synthesis waveshapes, finish lfo waveshapes, and a few other small things.  Sometime soon after I check every connection on the pcb and optimize the layout, I’ll order some sample pcbs and build one up. In the meantime, I’ll be finishing the software. I’ve got some ideas for making more complex waveshapes, morphing sounds and such. At that point it’ll be done.  I’ll have to do some documentation, but I’ve been doing a lot of that through this blog.  So, expect the release soon. I can’t wait.

DIY Voltage-Controlled Amplifier

The purpose of the voltage controlled amplifier is to make an amplitude envelope like this.

When I started the Rockit 8 Bit Synth design, I thought that I could implement a voltage-controlled amplifier, VCA, in 8 Bit land, saving precious hardware and everything would be easy. Well, as with many of the other things that I learned in the process of developing this project, reality would not be so kind. In this post, I’ll explain why that doesn’t work and then fill you in on how you can implement a functional Voltage-Controlled Amplifier using some fairly simple hardware.
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Make some quiet!

I’m making progress on testing the latest board and I got it making some noise. But, it’s not all the noise that I was looking for. It’s more!  Specifically, I made some layout choices that turn out to be quite poor.  Let me save you from making the same mistake.  Click through for the details.

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