Nucleus DIY VCF Kit

The River Synths Nucleus DIY VCF is a voltage controlled filter with discrete OTA core.

This is a full kit set in the Eurorack format. Most components have been pre-soldered as SMT parts!

Availability: In stock





  • Designed around discrete transistor OTA cores
  • Switchable resonance character with optional ‘Solid bass’ behaviour.
  • Switchable filter slope: 12 or 24dB/Oct
  • Pleasantly saturating input stage and resonance with higher levels
  • Linear and exponential FM options
  • Envelope and modulation inputs with independent attenuvertors
  • Soft-touch knobs and quality hardware (mostly Alps)

From River Synths:

The core of the Nucleus contains a newly designed operational transconductance amplifier (OTA) circuit, built from discrete transistors. While there are technically superior alternatives, a discrete circuit excels in providing a warmer and more lively sound.

My wish was to make the sound of the Nucleus as versatile as possible. After studying many different filters to identify the key to their unique sound, I decided to include a filter slope switch (12 or 24 dB/oct), and a resonance character switch with three distinct modes (see box).

In each of these modes, the low-frequency resonance behaviour can be further tailored with the ‘Solid bass’ feature, cleaning and firming up the low-end, or leaving it to boldly resonate.

Resonance character:

  • Neutral – Classic resonance, reminiscent of vintage 4-pole designs. Inherently with a loss of low-end at high resonance.
  • Q-comp – Similar to neutral, but compensated for loss of low-end. Providing a firm and stable resonant sound, with slightly different saturation character.
  • K-style – The beefiest of all modes, with a thick mid range and fat low-end, and an aggressive resonant sound.
 Concluding the design, I added a variety of modulation options for linear and exponential frequency modulation (FM), envelope modulation, and keyboard tracking (1V/Oct).

Specs & Downloads

Specs & Downloads

manufacturer River Creative
HP 8
Depth 39mm
+12V 47mA
-12V 47mA
+5V 0mA
Additional Resources Build Guide


Customer Reviews (1)

Excellent FilterReview by Xpump
I have some +20 VCFs including all the MOTM ones (in MOTM format) and I have to say that he results from building this VCF are really phenomenal.
The River Nucleus is in my top 3 VCF favs - very responsive and not a one trick pony.
The built-in CV attenuvertor exists on some of my MOTM filters and this feature should a requirement on all VCFs as it is quick to dial-in what you need w/o extra patching and add'l cv biasing. (Posted on 9/22/2016)

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