Tuesday, 27 September 2016

NLC Serious Filter - ARP Odyssey 4023

The Serious Filter it is based on the Arp4023.

 This is what it should look like when finished.

The ARP Odyssey mkI (model 2800), has the 2 pole 4023 12db/oct filter

The MkI 4023 been described as the most "Arp-like" sounding filter, because it doesn't try to imitate a Moog. The NLC 4023 also makes a nice quadrature oscillator.
The mkII in comparison, has the 4035 24db/oct filter - with a steeper bass roll-off curve, just like the minimoog filter.

The Korg-ARP Odyssey has all 3 filters. Would be nice to compare this with them when the build is done.

The rear virgin PCB 

Some NLC words of wisdom first: "Sausage Fears"
"Sausage fears": a term to describe the actions of straight men who are afraid of showing any physical or emotional bond to the men they are friends with. (The Urban Dictionary) 
So true... we men are afraid of showing emotion.

Back to the build:
First solder the two SMD TL072 ICs

Now the rest of the SMDs & headers.

Next, the regular caps, variable resistors & through hole diodes & resistors.

The 4 pots I've used are 100k B.
You could use an A pot on the signal input if you really want.

Andrew F usually uses B pots on most of his modules (except on the ADSR module). It is very easy to solder a resistor across 2 pins if you wish to turn a B/linear into an A/log pot. This way, you can also adjust the slope to suit your needs.

Don't forget to connect the ground tabs on the 6 jacks.
The completed module.

1. ARP Tech schematics for the 4023 filter
2. NLC Blog
3. NLC Build notes

More links to NLC (nonlinearcircuits) projects.

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