NLC Doof Drum Module - Build notes

These are my build notes for the Nonlinearcircuits Doof drum module.
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.
http://djjondent.blogspot.com.au/2015/03/nonlinear-circuits-dual-ota-vco-build.html
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 rest of the SMDs

I'm using a 10K on the RL ... LED resistor

Stuff in the through hole stuff:

pOTS & jacks next.

Now the LED. Get the orientation right. The anode is the long lead.

initial tests:

Initially, with a headphone, I found the volume very low and the LED didn't light up.
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.
:-)
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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
http://www.sdiy.org/pinky/data/Doof_Build&BOM_vers1.pdf
2. replacing the 10nF capacitor on the input with a link to

create 808 style extended drum hits with gates rather than triggers.

Links:
1. NLC Build Notes
2. Muffs : adjusting output level of the Doof
3. NLC blog spot 

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You can find more NLC builds here.

http://djjondent.blogspot.com.au/2015/03/non-linear-circuits-ncl-index.html

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