A mysterious forest wizard shot an arrow into a nearby tree trunk with a message wrapped around the shaft. It said "Wouldst thou deign to design a PCB for an exotic precious gem of a microchyppe which one canst obtaineth not except by exxtraction from a Casio FZ-1 or symilar keyboarde?" so I stuffed a message in a bottle saying "heck yes" and threw it on the water.
I had never heard of this chip or the fact that you can build it into a Eurorack module, but it's quite a unique thing. The chip is a "digitally" controlled filter and amplifier, which garnered some praise back when it was new for sounding analog. Turns out it IS more-or-less analog, with a switched-capacitor filter and hmm, I'm not sure how the audio amplifier is managed.
What is a switched-capacitor filter?????? Glad you asked. A filter is almost always a capacitor-resistor situation. A resistor reduces how much current can flow, and a capacitor can be thought of as a kind of balloon which "fills up" when a current flows into or out of it. Most synthesizers vary the resistance (sort of) to adjust the frequency at which a filter takes effect. You can do this with a potentiometer, which you need to turn with your hand like a cave man (ugh) or you can use a voltage-controlled resistive part like a Vactrol or an OTA which stands for operational transconductance amplifier obviously but just understand that it's MUCH easier to use a voltage to adjust the "resistance" section of a resistor/capacitor filter than adjusting the capacitor.
