DuckMixer progress

 

There it is. I'm thrilled with the texture and pretty happy with the layout and graphics, BUT I PUT THE SLIDER POTS UPSIDE DOWN!!!!

All the arghs and dangits and facepalming. I'm always so careful to put pots the correct way around, but this just tripped me up. There's two other adjustments I had to make to make this run of PCBs work well, (resistor value changes) but other than that I'm really happy with how well they work.

You can see my clever stereo pot mounting technique. You can buy stereo vertical-mount pots, but they're not common and they're expensive. And the PCB footprint is larger than this slot solution. If you mount stereo pots like this, definitely don't skip the nut on the potentiometer. The solder here may crack if stressed too much, so make sure to put the stress on the panel instead.

That's eight (8) vactrols. And a stack of op amps. I check each vactrol for the "fully lit" resistance, and match them to within 10 ohms. The typical value I've been getting with this batch is between 90 and 200 ohms when fully lit, and OL (over limit) for fully dark. 

The stack of chips are NE5532 amps, which, when stacked like that, are capable of driving headphones, and sounding pretty dang good while they're at it. They suck up quite a bit of current, and get excitingly warm, so if you're wanting a low-power module, choose a shorter stack, or no stack at all, or even more crazy? put in a TL072. Those use less current.

What is next? I'll tell you what's next! I'm flipping the pots to the right way up (aaarrghghghg), adding simple buffers on the inputs to hide the variable impedance from upstream modules (still not sure I'm gonna do this) and for SURE adding a ZV.HP high pass VCF to the sidechain mix-in signal path. More people need to use the ZV.HP it is SUCH A GOOD LITTLE FELLOW!