My Own Input Module

To close the 4HP gap at the bottom left of my synth case, I added a last input module. It will allow me to enter some external signals and bring them to the voltage level of the modular synth.  Moreover, it has its own piezo microphone.

It is modelled along the lines of Music Thing Modular Mikrophonie and Mutable Instruments Ears.

Input module

One input, an amplifier and an envelope follower for good measure.

The design is based on the original schematic for Ears from Emilie Gillet.  I kept the input gain stage. Due to space constraints, I had to simplify the envelope follower. I’m still doing pass through breadboard here, so this is not dense enough to have the same features as a full fledged Ears (or Microphonie Mk2 for that matters).

It took me a while to figure out the details. I had one operational amplifier available. The other being used by the gain stage. I was going for a short attack but not so short release with the right amount of filtering. Still not perfect : the shape is good enough but I fear that without the proper buffer at the end, I may not be able to drive any type of circuit.

 

 

Breadboarding the circuit : envelope follower output on top.

Piezo attached, other for scale

As I wanted to have some bumps to be able to scratch the surface above the piezo, I went with a different technique for the front panel.  It is the technique I used for the previous 2HP modules I made : dremel some lines and blacken them.
 

Bob helps with the panel

 

 

 

 

 

 

Mistakes I made include cabling the potentiometer in reverse (was expected), having a diode badly placed (more problematic) and connecting the piezo to the output instead of the input (confusing left and right duh !).

Debugging

Finished PBAs

 

 

 

 

 

 

 

 

 

 

 

This is the densest design I made this way. I begin to feel the limit and a desire to do things differently. I will change the technique for the next designs. In fact I might revisit the first modules I made, shrinking them in the process.
 

On the side

Here it is. Bottom left.

The completed case

 

And here are some sound examples where the module microphone is used for sound effects. Electric bass and synth pads are treated by the synth through the jack input.

Jay F. · Should I Come In

Finally, should you be interested, the schematics and layout.