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Intensive Care Audio Vena Cava Filter

Filter & Ring Modulation Distortion Pedal By Simon Small
Published June 2021

Intensive Care Audio Vena Cava Filter

London‑based Intensive Care Audio take their branding seriously: not only is this pedal named after a medical device, but it arrived packaged in a prescription bag accompanied by a medical‑style ‘information and warnings’ pamphlet! It’s all good fun, but it’s worth mentioning that a note is also included to inform the user that all of this packaging, including the bubble wrap, is recyclable.

While the Vena Cava Filter is a distortion pedal at heart, you won’t find traditional controls here: the main functions of this pedal are an auto-filter and ring modulator, though you can still use the pedal as a straight‑up distortion, as there’s a Blend control that allows you to mix from pure distortion (fully anti‑clockwise) to filtered and ring‑modulated distortion (fully clockwise). The Gain knob controls the amount of gain in the distortion circuit, whose effect ranges from light overdrive to heavy distortion. The Volume control sets the output level from the pedal, of course, and this is handy when you want to crank the gain because this pedal can get very loud! The distortion feels responsive, and when the gain is cranked it is extremely thick and really satisfying to riff with. Adjusting my guitar’s volume control, I found I could also achieve more subtle but still driven tones.

The main functions of this pedal are an auto-filter and ring modulator, though you can still use the pedal as a straight‑up distortion.

On the left side of the pedal, you’ll find the Wave Function control, which is a rotary switch that allows you to select one of eight LFO Waveforms that will sweep the auto‑filter and ring modulator. From left to right these are: Random Slopes, Random Steps, Sweep, Sine, Triangle, Square, Ramp Down, Ramp Up. I found the choice of LFO waveforms exciting, as they give access to such a variety of modulation, ranging from a nice predictable sine wave to utter mayhem with random steps.

Moving across, the Freq knob sets the frequency (ie. speed) of the LFO. This can also be set using the tap‑tempo footswitch on the bottom right of the pedal. The speed and waveform are visually displayed by an LED under the Wave Function control. The Freq control can take you from slow pulses that feel like they barely move to ultra‑fast chopping — it’s a really musical‑sounding control and great fun to play with on a rung‑out chord or drone.

Now, as per the company’s strap line, things can “Get Weird”. The LFO is used to control the sweep on both the auto-filter and ring modulator, and I’ll consider the filter first. The pedal features a state variable filter, with the Peak knob controlling the filter’s notch‑width and intensity. When set fully clockwise the notch is at its narrowest and gives you an intense filter band. It’s very aggressive and cycles in a beautifully crushing manner. You can reduce the intensity of the notch by turning anti‑clockwise. Below is a toggle switch for Voice. When engaged, this shifts the position of the notch in the filter higher up the frequency range, so essentially this is a ‘high/low’ switch.

The Ring knob sets the base frequency of the modulator, which is swept by the LFO. You’ll find that results may vary according to which wave function you’ve selected for the LFO, but at settings below 12 o’clock the carrier frequency becomes inaudible while still producing interesting stuttering effects. Further experimentation with the Ring knob will lead you to glorious sample‑rate‑reduction effects and other familiar ring modulator territory — there’s ample scope here for ‘exciting’ your signal. Turning the knob fully clockwise disengages the effect.

Intensive Care Audio say that this pedal should be prescribed to treat “Bland Guitar Syndrome and Excessive Aural Dryness.” It certainly cured this for me!


£189 (about $263 when going to press.)