Simple Sequencer Schematic. Used in MS-20 mini mods.

I've had a lot of requests for the schematic of the sequencer I used in my MS-20 mini mods. I've been very busy, but I finally drew them up all nice and perdy. 
The circuit is a super simple one based off the 4017 decade counter IC. The clock input can be from anything with a pulse like the MS-20's square LFO, Volcas, drum machines, ect. I didn't hook up the reset due to lack of space on the MS-20 mini's chassis. This circuit gives you a gate and CV output for fun step sequencing. 
The 4017 is powered by the 9 volts inside the MS-20. 
Here is a Larger Image.
I admit that this circuit is very rudimentary and additions can be made to add more features. You can add jacks to each step so you can change the length of the sequence using the reset line. So many possibilities. 
I added switches on mine so you can choose to engage or disengage the gate for individual steps for fun rhythms. 
I also want to add a portamento switch that engages a portamento between steps. I'll document this when it's done.
If you want to get really fancy, you can throw a microcontroller into the MS-20 and read off the MIDI from the MIDI port and get clock signals to MIDI sync you sequencer. Leave a comment with any fun additions you do. 

In other news, I have resigned from Ernie Ball / Music Man and accepted a job in San Francisco with Quirky. I want to get involved in the synth scene here. I am pretty sure it has to be bigger than SLO's. Let me know if you life in SF and want to make music or need repairs or anything. 


Moog Circuit Bending Challenge 2014 Entry

The competition rules stated that the bend had to cost less than $70 dollars, run off 9V batteries, and be repeatable. Source code and schematics will be available via GitHub in the coming weeks (once I clean it all up)

I bent a Yamaha DD6 to mash up drum samples using an iPad.

I used an Atmel XmegaA3BU Xplain board as the brain along with an Intersil crosspoint switching matrix IC. The Xmega communicates with an iPad via USB by functioning as a class compliant USB MIDI device. There are 3 buttons on the board; an up, down, and enter button. When the device first powers up, it is in the "HOME" screen. The "HOME" screen also acts as a way of clearing a preset so the DD6 can go back to stock when using the device, by pressing enter when "HOME". Any of the 10 presets can be recalled by scrolling to them and pressing enter. The last position in the menu is a "RANDOM" setting which creates a random preset. 

The app on the iPad allows you to make connections on an 8X16 grid, which creates 3.4e38(!!!) possibilities. Using the iPad, you can save your preset to one of the 10 available preset locations on the device. With the iPad, you can also clear all the connections or make them all. 

I also added a sync out from the DD6. This sync allows me to clock an external sequencer or even a Korg Volca. 

Here are some of the videos:

This video is actually the last video, but it includes a discussion of the overall project and sound demos at the end. 

Going over the hardware.

The iPad app and it's code

XMega firmware code


Inside the Volca Beats

As with the Volca Bass, I found no suitable room for a MIDI jack so I just broke out the labeled test point and will install a 1/8" stereo jack for the MIDI.


Inside the Volca Bass

Had a solid hour of fun with the Bass before I popped it open. 

I was hoping to add a MIDI jack to get MIDI out since it is clearly labeled:
I couldn't find space in the case to place a DIN jack so I am going to order a couple stereo 1/8" jacks to break out the MIDI that way.

I didn't do anything too crazy; just broke out the marked test points on the PCB

The jacks fit perfectly

Interesting that the SMD LEDs are on the other side of the PCB and they shine through holes

Used the ground point from the battery

Left an extra hole for the MIDI

 The jacks let me patch into both waveforms from all 3 oscillators, and the raw signal out of the VCO, VCF, and VCA.

Korg Volcas Arrived!

The Korg Volcas that I ordered back in February finally arrived! I ordered the Bass and Beats since I have enough keys. Come Monday, they will probably be modded. This might just be the last recording of them before they have some fun with my soldering iron.

Synths used in this recording: Korg Monotribe, Korg Volca Beats, Korg Volca Bass, Korg MS-20 mini, and Roland JX-8P. Volcas and Monotribe are synced via the sync jack. JX-8P is synced to the Monotribe via MIDI. Sync out also goes to the sequencer clock on the MS-20 mini and is used for both filter sequencing and pitch sequencing.


Mooer Pitch Box Pedal Teardown

Finally got around to ordering one of the new digital Mooer pedals. I was always curious how they could make pedals for so cheap. After a few minutes of noodling with it on the Rhodes and guitar, I popped it up. 

4 screw on the bottom take the back off. 

Removing the jack and switch nuts lets you remove the whole PCB.

Little mini board in the middle. I bet there is something under it too.
Big ol' IC under there. 

But whats under the blue sticker?!

 Alpha selector switch. 

Nowhere on the PCB does it mention Pitch Box, so I am assuming this is a digital pedal. Silkscreen looks super cheap and the case is a very light weight metal, but everything else doesn't seem too cheaply done.