In my recent experimentation with several granular modules - Arbhar from Instruo and Brinta from Error Instruments and TiNRS - I have found myself more and more often wanting to use Arbhar's condenser microphone to feed Brinta some external audio. You see, Arbhar's mic sounds excellent, and granular modules in general seem to play VERY nicely with direct recordings - even just the sounds of patching or snaps and pops near the microphone. Typically, this would be as easy as patching Arbhar into Brinta and having at it, but here is where my problem began. As you may know, Arbhar is not only a granular synth - it also provides an excellent end of chain reverb! Obviously, I can't be unpatching my end of chain modules every time I want to feed Brinta some new content, so I started digging...
I went looking for other microphone modules that could fill this function, but none of the available options quite met my requirements. Most modules containing microphones seem to bundle that mic in with a number of other features - samplers, granular engines, etc - or simply use the wrong type of mic for my purposes - contact mics instead of condensers. After deciding that the simple, compact, intuitive microphone-in-a-module I was after was yet to exist, I got to work!
First, I had to decide on a circuit architecture - there seemed to be several typical driver circuits for these electret condenser capsules; discrete transistor circuits and purpose-built electret driver chips. I decided to go with the latter to save on space and keep this compact. The MAX4466 amplifier seemed like the perfect candidate - and I wasn't disappointed! After building my board files, starting with the example circuit from the amplifier chip's datasheet and adding some additional features since this needed to work well at eurorack levels, I sent the files off for manufacturing. It was a tight squeeze to route in some areas, but it came out very compact and tidy!
A few short weeks later, the boards (mainboard and panel) arrived at The Lab. I assembled the first unit, went to test it, and immediately discovered a crucial issue - there was no sound coming from the module for some reason! I went back to my files and the datasheets for some suspect parts, and discovered I had accidentally swapped the pins of the mic capsule. Luckily, it was a simple task to desolder the capsule and reinstall it "backwards." after another round of testing, I realized I had also flipped the gain control knob on the schematic - even after designing several modules, this still happens from time to time! The primary gain control worked as expected, so it was only the large knob which needed to be updated for the next revision. Also, the output sounded excellent for what I had been expecting, but was a bit on the quiet side so the new revision needed a bit more gain on the secondary stage as well. I had included a jack light so it would be easy to tell if the module was working without having to listen to it, but in my testing decided this was an unnecessary feature as it went almost entirely unused.
After spending some time tweaking the design to resolve these issues, I sent off the new files for another run. This time, everything works just as expected, so it's off to the Curio for Hey! Lovingly named during the development process by my good friend Wray over at Swamp Flux. Now here are the specs:
Hey!
1u6hp
Condenser Microphone
Gain control for primary gain stage
Attenuation before fixed secondary gain stage
Skiff-friendly single board design
Depth:
30mm (with strain-relief)
25mm (with no strain-relief)
Either Way power:
+12v: 14mA
-12v: 5mA
+5v: N/A