Jurgen Haible Varislope Filter/Phaser PCB

J├╝rgen Haible's 6 pole filter, realzed with OTAs and combined FET / Bipolar buffer stages. . These are NOS stock PCB's.

This is a PCB suitable for multiple formats.

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From Jurgen Haible:

"Variable Slope Filter / Phaser "
  • Powerfull 36dB/Oct LPF (6-pole Filter)
  • Variable Filter Slope (voltage controlled)
  • Resonance
  • Phaser with equal poles, or spread poles (voltage controlled)
  • "Everything between filter and phaser" (combination of APF and LPF stages)
  • Unique on-board LFO with volzage controlled waveform-crossfading
  • Audio-Rate and Random Sample & Hold Modulation
  • Standalone FX (with 16V AC wallwart) or +/-15V Synthesizer Module
  • No need to implement everything - omit half the components and still have the 36dB/Oct LPF ...



A mean little module from my JH-3 Modular. 

6 filter poles, realzed with OTAs and combined FET / Bipolar buffer stages. 

Variable Slope function for 6-pole VC LPF. 
Voltage controlled Pole Spread for Phaser mode. 
Zeroes switcahbel in pairs, i.e. a lot of combinations of all pass and low pass stages. Positive and negative feedback. Positive and negative wet/dry mix. Rather special overdrive behaviour (Dirty!), and (IMO) pleasant way of breaking into oscillation.

Audio Sample 1 
(Arpeggio from OB-8, with delay and reverb. First few seconds dry - then playing with phaser.)

Audio Sample 2 
(This is something I recorded a few years ago. I don't remember all the details. But it was a Split on the OB-8, bass sound on left hand and organ sound on right hand, and the whole thing was processed with the Variable Slope Phaser / Filter to get that "pulsating" sound. Lots of delay and reverb as well, obviously.) 

Audio Sample 3 (First few seconds: Unprocessed input signal. Then all kinds of modulation, mostly sample and hold and self-modulation, high resonance. Towards the end of the clip, input signal is removed, and phaser runs on the edge of self-oscillation. Don't turn it up too loud - danger for your ears and speakers! Everything is modulated with the on-board LFO only!)

Audio Sample 4 (Living VCOs thru Varislope Filter: Everything from Fat and Smooth to Harsh. Fat because of 36dB/Oct Filter Slope! Only using the on-board Modulation LFO and S&H, plus an external envelope generator.)

Audio Sample 5 (Mostly Phasing. Input signal is a ARP-Omni-like sound from the JH-3200. First Dry. Then starting with rather ordinary phasing, and on to stranger things.)

The Variable Slope Filter / Phaser will get a very special on-board LFO that is derived from my JH-4 synthesizer. 
Voltage controlled Rate and Depth, of course.

But there is is more: 
You will be able to crossfade between waveforms with a potentiometer, or with another control voltage. 
Starting from ccw end, the waveforms will be: 
Triangle, fading into Sine, fading into Square, fading into Sample&Hold, fading into audio rate self-modulation.

Let me explain that choice: 
Triangle fading into Sine means rounding the edges. 
Square fading into S&H means rhythmic modulation with more or less randmness thrown in. 
S&H fading into audio self modulation means mixing and fading two different flavors of madness. Especially with high resonance. 

Specs & Downloads

Specs & Downloads

Manufacturer RandomSource
Depth No
+12V No
-12V No
+5V No
Additional Resources Build Guide & Bill of Materials


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