SO HIGH SO LOW: Dual Resonant High Pass / Low Pass Filter & Preamp Inspired by MS-20

The SHSL combines MS-20 style dual resonant filters with a Moogerfooger-inspired preamp. Both filters feature independent cutoff and resonance controls, with dedicated CV and expression inputs for voltage control. The preamp ranges from clean boost to saturated overdrive. Designed for guitar, bass, synthesizers, and drum machines, with seamless modular integration.

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SO HIGH SO LOW Highlights

Two Fully Controllable High Pass and Low Pass Filters Arranged in Series

Each filter has independent cutoff and resonance controls. When combined, these filters create a bandpass mode - a hallmark of classic MS-20 synth family that surpasses the limitations of switchable filter designs. Both filters self-oscillate when resonance exceeds the oscillation point, allowing the SHSL to function as a dual CV-controllable sine wave oscillator. The series arrangement provides maximum flexibility: use one filter alone, both in parallel frequency ranges, or create a swept bandpass by converging cutoff frequencies. This topology delivers everything from gentle resonant sweeps to aggressive filter screaming.

A Powerful Preamp for Saturation, Overdrive & Distortion

SHSL has a dedicated preamp section which is inspired by Moogerfooger pedals providing beautiful coloring to the sound. The pre section can operate in array of modes from light saturation to pushing the amp into overdrive/distortion territory. Located before the filters, the preamp shapes your input signal before filtering, adding harmonic complexity and driving the filters harder for increased resonance and character. This arrangement mimics classic synthesizer signal flow where VCAs drive VCFs. The preamp transforms the SHSL from a transparent filter into a complete tone-shaping tool, adding weight to bass, grit to guitars, and warmth to digital synths.

CV and Expression Controls for Each Filter

Separate CV and expression inputs for each filter provide complete dynamic control for live performances and effortless integration with modular systems. So High So Low can also be used as a standalone CV controllable synth / oscillator. CV inputs accept ±8V control voltage from sequencers, LFOs, envelope generators, or any modular source. Expression inputs allow standard expression pedals to control filter cutoff in real-time, functioning like a voltage-controlled wah pedal. This dual-control architecture enables complex modulation routing: sequence one filter while manually controlling the other, or use LFOs to create rhythmic filter pumping. The SHSL bridges guitar pedals and eurorack worlds without compromise.

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Applications

1

BASS GUITAR

Deep filtering with preamp saturation. Self-oscillating filters add sub-octave drones. Expression control for dynamic filter sweeps during performance.

2

SYNTHESIZERS

External filtering for digital synths lacking analog filters. Modular integration via CV inputs. Dual oscillator mode for drone synthesis and sound design.

3

GUITAR

Experimental filter effects and resonant tones. Preamp overdrive with filter shaping. Expression-controlled wah-style sweeps with MS-20 character.

4

MODULAR EURORACK

Dual VCF with voltage control. Self-oscillating mode provides two sine wave oscillators. Integrates seamlessly with sequencers, LFOs, and envelope generators.

5

DRUM MACHINES

Filter processing for electronic drums. Resonant kicks and snares. Rhythmic filter pumping via CV sequencing.

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SO HIGH SO LOW In Action 

Controls, Overview & Operation

FEATURES:

  • High Pass & Low Pass Filters
    High Pass and Low Pass resonant filters inspired by MS-20 with separate cutoff and resonance controls. Filters are arranged in series and have controllable resonance. Past the oscillation point each filter begins to self oscillate and can be used as a CV controlled oscillator.
  • Preamp
    SHSL has a dedicated preamp section which is inspired by Moogerfooger pedals providing the beautiful colouring to the sound. The pre section can operate in array of modes from light saturation to pushing the amp into overdrive/distortion territory.
  • CV & EXP controls
    Separate CV inputs for each filter allow to control the pedal with the external controllers like Korg SQ-1 or Arturia devices. You can also sync it with your modular or semi modular system. Separate expression inputs for each filter allow controlling the SHSL with the expression pedal.

CONTROLS:

  • Master: Sets the overall output volume.
  • Preamp/Saturation: Rotate clockwise to add gain from the preamp section, which produces a darker, full-bodied, and saturated sound.
  • High Pass:  Rotate clockwise to strengthen the high pass. As you turn the knob to the right, fewer low frequencies will remain, allowing only the high frequencies to pass through the filter.
  • Low Pass: Rotate counterclockwise to enhance the low pass. As you turn the knob to the left, fewer high frequencies will remain, allowing only the low frequencies to pass through the filter.
  • Resonance High: Sets the amount of amplification for the high frequencies around the cutoff point of the high pass filter. Increase the amplification by rotating the knob clockwise. The filter will begin to oscillate beyond the OSC Point.
  • Resonance Low: Sets the amount of amplification for the low frequencies around the cutoff point of the low pass filter. Increase the amplification by rotating the knob clockwise. The filter will start to oscillate beyond the OSC Point.

Demo 1

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Demo 2

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Demo 3

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Demo 4

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Demo 5

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Demo 6

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SHSL F.A.Q

So High So Low high pass/low pass filter and preamp based on Korg MS-20 filter and Moogerfooger preamp.
There are demos on YouTube, on our web site and Instagram.
The filters are arranged in series.
Yes, the high pass and low pass filters are arranged in series, so you can use them as a bandpass.
Yes, you can connect CV to both: high pass and low pass filters.
You can connect your expression pedal to either high pass or low pass input and control the cutoff with it (similar to a wah pedal for example).
Absolutely! SHSL loves bass and it is a terrific combo.
Not to run the So High So Low pedal on anything higher than 9V. Otherwise you'll fry the pedal.
Only 9V center negative (Boss type) power supply is supported. There is a voltage conversion inside the pedal and it will fry if you connect a higher voltage. The minimum current must be 200mA (though 300mA is recommended for proper operation)
SHSL needs current of minimum of 200mA, though we recommend 300mA minimum for stable operation.
Yes, both filters can oscillate when the resonance is past the oscillation (OSC) point.
Yes, So High So Low is a true bypass.
No, we have taken care that SHSL runs on a standard 9V Boss type power supply. We are boosting the voltage internally for the proper operation of the filters and preamp.
So High So Low  is a mono pedal.
The preamp is located before the filters. 
SHSL has expression controls for each filter cutoff and two CV inputs: one for high pass, one for low pass.
Yes, we are shipping worldwide.
Moreover, SHSL will is available with the selected UK and USA dealers.

WHERE TO GET THE SHSL

The SHSL is available for purchase directly from the AMCO store with worldwide shipping, or through one of the following venues

THE USA LOCATIONS

THE UK LOCATIONS

Downloads

SO HIGH SO LOW MANUAL

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