Thursday, 27 August 2015

Chopper/Bi-Di router - NLC build notes.

These are the build notes for the nonlinearcircuits Chopper / Bi-directional module. 
So what is it?
It's a eurorack format voltage controllable electronic switching module.

The bottom section is similar to your old fashioned gate controlled bi-directional router. Functionally, it behaves very much like the Serge triple bi-directional router, though the circuit is very different.

The top section is based on a 70's delta modulator, (at least in concept). Delta modulation (DM or Δ-modulation) is an technique of analog-to-digital and digital-to-analog signal conversion. It's used for information transmission where quality is not of primary importance.

The signals being switched are also sent through a comparator & they control the switching. Plus you can add CV to all of this. Cool !

Muff's thread is here:

Andrew's build notes are here:

Andrew's Blog:

 I have  2 versions of the PCB.
I'm currently building Version 2 (on the left).
Version 2 has corrections (mods) already done which you will read about in Andrew's build notes.
Mostly replacing some resistors (470K & 22K) & the addition of the 10K .

A 10 k resistor needs to be soldered from the left pad of the 470k resistor to +V, easiest is the closest pin of
the nearby transistor - the collector of BC547.

I've used two 68uf ceramics for the decoupling caps.
I've used 510 ohm SMD resistors for the  LED resistors.
You need to experiment with this. I might go to a 1K for the next build.

Mount pots & Jacks. I used a 1M & a 100K pot ... using this for CV.
Cool. Looks like it works. 


You can find more NLC builds here.


  1. I found this blog after a long time which is really helpful to let understand different approaches. I am going to adopt these new point to my career and thankful for this help.
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    1. Glad you found this helpful. I'll do similar posts for all my NLC builds