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#13 - MAD 1.1 - What's boiling in the pot

A project log for MAD - Modular Audio Devices

A set of Eurorack modules to control synths, make custom MIDI-compatible interfaces and USB audio, powered by Teensy 3.6

Michele PerlaMichele Perla 03/22/2018 at 17:410 Comments

Hi folks!

It's been a long time. 

A time during which I changed country (again), a time in which I did not stop working.

In fact, I have some nice news: MAD 1.1 is almost ready.

WHAT WE LEAVE

The PSU is no more; since the project is shifting towards the Eurorack format there's no need to reinvent the wheel since most Eurorack cases come prepacked with a nice and powerful PSU.

The main modules are not going to be stackable on top of each other (maybe except for the IOAPEX, more on that later). Also the idea of having small modules that would interconnect with each other using pin headers is gone, too. Eurorack means that the modules will all be on one big front panel, so it's kinda difficult to mate modules set in this fashion. This led to the integration of some old submodules into bigger main modules (like the CODEC, which is the old CORE+IN+OUT modules).

The IOAPEX will have 128 instead of 256 digital IOs and analog ins, why? Because it's so much easier to find the 44-pins XC9572XL than the 64-pins one. Also, the digital IOs can be set up to scan matrixes, so there's still PLENTY of room for controls.

WHAT WE GAIN

More features than before! 

Having to redesign for Eurorack made me lose the ability to stack modules on top of each other, making the use of a single Teensy 3.6 to drive multiple modules trivial. 

This is why I decided to make the CORE a standalone module, not just a simple codec breakout. At first, in early v1.1 design phases, I thought that the CORE would provide just a USB port for PC communication and two MIDI ports for the sake of utility. But I also always thought of adding a TFT display to handle device configuration without resorting to custom tools on a PC, and I also always looked for a way of using the two DAC channels of the Teensy to do something useful. Finally, I also wanted to justify the eventual price tag of a mandatory module in case someone wants to use the IOAPEX and/or a CODEC to make their own MIDI control and/or USB audio interface. 

So, here comes CV! The two DACs are going to be multiplexed to provide 8 CV channels, which will be used by default for Note, Velocity, Pitch bend and Modulation, along with 8 Gate channels which will be used for note gating, and for clocks. These CVs will be mapped either to USB-MIDI or to physical MIDI channels, and with a bit of software juggling they could be used to make, say, step sequencers, or to make 8 Note CVs instead of just 2. This would make a neat addition in any modular rack!

As I said in the previous "chapter" the old CORE becomes CODEC, which will integrate the old IN and OUT modules in one big Eurorack module. The new CORE will have a custom header that will connect to the CODEC by means of an IDC cable. The new CODEC module will still retain the expandability features seen in the previous IN-OUT modules, so to have guitar buffers, mic preamps, phono preamps, passive speakers outs etc. 

About the IOAPEX, since it will not provide any directly usable control in an Eurorack system, it will probably stack behind a CORE module. The user will then branch the IOAPEX submodules (with pads, buttons, encoders etc) to the IOAPEX using IDC connectors; in this way the IOAPEX will not take valuable rack space, leaving room for other modules.

Conclusions

It's been almost a year since I started working on this project, and it's finally taking its real shape. I still envision a crowdfunding campaign, which will only happen after I get a full set of prototypes in a rack and show them off at various expos (Maker Faires, Synth meetings, etc). I'd also like to get a collaboration with some hardware manufacturer to make custom Eurorack cases with FATAR-style keyboards that would connect to the IOAPEX, but that is a bit more far-fetched at the moment. 

Of course, to do all this I need some finances. I got some savings (yay, I adulted :D) but still I would love to have extra cash. Participating in an expo is not cheap, especially when you consider that a person alone can't go to a three days convention; this means that for every expo I need at least one more person with me, which means double the costs for food, hotels, transports etc. 

We'll see if this round of funding will be helpful :) 

Cheers,

Mick

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