Adding CV and gate to the Cellz

 The Cellz is one of the more inexpensive modules, mostly because its functionality often isn't good enough and it is outgrown and replaced by a proper sequencer. However, with a small amount of work it is possible to add CV and gate to the Cellz, increasing its useful lifespan and perhaps even good enough to purchase one (I got my spare for US $44).

Adding CV allows the Cellz to be used as a quantizer, and in combination with stepping through all the sequencer steps this can also be used to automatically record quantized phrases into it. Here is a short video of what the project looks like:

As you can see, when the gate is high, it passes through the voltages from CV and quantizes them, and when the gate is low it keeps the last quantized value of that cell.

The circuit is reasonably simple. For each potentiometer on the Cellz I bent the middle pin and unsoldered it. I added header pins to the three places of the PCB where the potentiometer is connected and placed diodes between them, so that the middle pin can't exceed the values of the outer pins. The jack is connected to this with a 1k Ohm resistor and the pin of the potentiometer is connected to the switch of the jack, so that the Cellz continues to work normally when no plug is inserted.

For the gate the emitter and collector of a transistor are placed over the switch (one side of the switch is ground, and one side of the potentiometer is ground as well, so you only need to have one wire for both) and the jack is connected to the base of this transistor using a 15k Ohm resistor. There is already a 10k Ohm pullup resistor for the switch in the Cellz, so no other components are needed.

In total you'll need 8 wires from the Cellz: 5V, 0V, 2x2 for each potentiometer, and two wires for the switches. You may not need to use header pins on the Cellz side, except for the middle potentiometers, because there you may want to be able to plug in the wire back onto the header so you don't need the expansion board if you don't want it.

I used header pins everywhere, except to hook up the potentiometers, for which I just cut one female header jumper wire in half and soldered it to each of them.

I'd recommend shorter jumper wires than I used (20cm) but these were the ones I had and therefore the ones I used.

I also added a more detailed picture of how the potentiometer looks after desoldering the pin. This is the hardest part, as the Cellz uses lead-free solder which means you iron needs quite a high temperature (>400 degrees Celsius) in order to do this. First I sucked up some solder with the solder sucker, then I used a screwdriver to pull the pin out. With pliers I straightened out the pin and soldered the wire to it.

At the bottom of this post is the schematic. The header doesn't match the one I soldered together, but it is up to you how you want them to be hooked up.