It's Eurorack format.
This is a very different circuit from the 808 & 909 clones doing the rounds today.
Can't believe I would ever tire of those sounds but its great to have something different.
This circuit uses a trimmed down NLC dual OTA VCO and the VCA from the NLC matrix mixer
(a future build).
I built the OTA VCO over a year ago.
That VCO used a OTA or Operational transconductance amplifier.
The topology is common enough in many drum synths: Trigger circuit, envelope follower, VCO, VCA.
Get started with some tanning. It's the Aussie way.
Firstly the virgin PCBs & faceplate:
First get those !Cs in.
Now the LED. Get the orientation right. The anode is the long lead.
The LED resistor I used was a 10K. This is for super bright LEDs.
I swapped it for a 1K and noticed a sudden increase in volume & that the LED lit up.
I decided to do another swap. This time for a 510 R.
Much much better !!!
Very loud and the LED lights up nicely thanks.
Andrew F suggested that in order to get a bigger output, I change the 220k next to the TL072
He has taken it to 4M7 ...which is way OTT, ....bounces off the power rails.
Maybe a more sensible range would be between 1M5 & 2M2.
For the moment I'm really happy with the standard Doof module.
Other mods include
1. CV control of decay instead of freq... see build & BOM pdf
2. replacing the 10nF capacitor on the input with a link to
create 808 style extended drum hits with gates rather than triggers.
1. NLC Build Notes
2. Muffs : adjusting output level of the Doof
3. NLC blog spot