The Intensive Care Audio Vena Cava Filter is a distortion pedal with an auto-filter and ring modulation in one box. The distortion side ranges from mild overdrive to heavy, fat distortion, while an LFO (low-frequency oscillator) sweeps both a notch filter and a ring modulator across your signal1. It is one of the medical-themed pedals made by Intensive Care Audio, a London company whose name was chosen before the COVID pandemic hit2.
Guitar Pedal X's Stefan Karlsson described it as a 4-in-1: filter, oscillator, distortion and ring modulation3. He also noted that despite the name, he mostly uses it as a modulated distortion, where it delivers a textured gain voicing that "can get noisy in the best way"4.
Controls and how it works
The pedal has five knobs, two toggle switches, an 8-position rotary waveform selector, and two soft-touch footswitches. The left footswitch is BYPASS and the right is TAP TEMPO, so you can set the LFO speed by tapping along with the tempo1.
| Control | What it does |
|---|---|
| BLEND | Sets the mix between distortion (fully counter-clockwise) and filtered/ring-modulated distortion (fully clockwise)1 |
| GAIN | Sets the distortion gain, from mild overdrive to heavy, fat distortion; at lower gain settings the filtering effect becomes less pronounced1 |
| VOLUME | Sets the output level3 |
| RING | Sets the base frequency of the ring modulator, which is swept by the LFO along with the filter; fully clockwise disengages the ring modulator1 |
| FREQ | Sets the frequency (speed) of the LFO, indicated by the LED above the control1 |
| PEAK | Sets the depth of the LFO controlling the filter notch and the ring modulator frequency5 |
| RING SWITCH | Removes the LFO from the ring modulator frequency so the ring modulator can be set at a specific, fixed frequency5 |
| VOICE SWITCH | Selects between two filter voicings, one a narrower notch with emphasis on high-frequency content1 |
| WAVE FUNCTION | 8-position rotary switch selecting one of eight LFO waveforms1 |
The RING control rewards experimentation. At settings below 12 o'clock the carrier frequency becomes inaudible and produces a stuttering effect, and set correctly it can create octave-down effects that move around with the LFO's wave shape when swept5. Guitar.com's reviewer found the distortion circuit alone is bright but smooth, getting seriously gainy toward the top of the dial and somewhat scuzzy near the bottom, with no clean options6.
The eight LFO waveforms
The WAVE FUNCTION rotary switch selects one of eight LFO waveforms1:
Guitar.com's Richard Purvis walked through what each shape does to the sound. Left of the sine wave, a stepped wave makes things just a little less smooth, a random stepped wave (sample-and-hold) takes things into glitchy territory, and a random curve arcs around at will like a broken auto-wah pedal. Right of sine, an up/down square is good for aggressive tremolo-like effects, a percussive down-ramping mode gives sci-fi laser pew-pew, and up-ramping "sounds properly scary" at faster speeds6. With the sine wave engaged, he found the filter's chewy swirl a perfect match for the character of the distortion: bold and biting, but eminently likeable6.
Power and connections
The Vena Cava Filter runs on a 9V center-negative power supply, and Intensive Care Audio specifies using only high-quality supplies1. Current draw is 65mA2.
The maker specifies 9V center-negative power only, with no battery option, so plan on a dedicated pedalboard power supply rather than a battery.
Versions and the smaller enclosure
The pedal was originally released as the VENA CAVA FILTER Distortion v.15. In November 2021 it was updated to a smaller enclosure, though not a compact one2. The current version sits in a black wedge enclosure measuring 126 mm long, 88 mm wide, and 45 mm down to 27 mm high, weighing 395g16. The v.1's waveform list named Triangle and Sweep where the current maker page lists Step Up/Slope Down and Steps, but the eight-position format is the same15.
What reviewers said
Reviews were positive across the board. Pedal of the Day wrote simply that they love the Vena Cava Filter Distortion v.15. Guitar.com rated it 9 out of 10, concluding:
"It's barmy, but you're never far from an interesting and usable sound."
Richard Purvis, Guitar.com6
He found the pedal remains musical at heart, with insane sounds but conceivable real-world uses for quite a few of them. His criticisms were about what is missing: an envelope-following mode would have been nice, and the ability to control the LFO speed with an expression pedal even nicer6. Guitar Pedal X's Stefan Karlsson named it one of his very favorite distortion pedals of 2023, calling it a superb combination of filter, distortion, oscillation and ring modulation3. His go-to setting at the time was Blend, Gain and Volume at 3 o'clock, Ring at noon, Frequency at 2 o'clock, Peak at 10 o'clock, both switches down, and the LFO on the square wave4.
Videos
INTENSIVE CARE AUDIO
Pedal of the Day
Jackson Brooksby
News
Questions
Does the Vena Cava Filter have tap tempo?
Yes. The right of its two soft-touch footswitches is a tap tempo switch, so you can set the LFO speed by tapping in time with the music. The LFO speed and waveform are also shown by an LED above the FREQ control.
Is the Vena Cava Filter true bypass?
Yes. Intensive Care Audio fits the pedal with soft-touch, relay-based true bypass, so your dry signal passes through untouched when the pedal is switched off.
Can the Vena Cava Filter do octave down sounds?
Yes. Set correctly, the ring modulator can create octave-down effects, and when the LFO sweeps it, those octave tones move around with the wave shape selected by the WAVE FUNCTION switch. Below 12 o'clock on the RING control, the carrier becomes inaudible and produces a stuttering effect instead.
Can you use an expression pedal with the Vena Cava Filter?
No. The pedal has no expression input, and Guitar.com's reviewer noted that the ability to control the LFO speed with an expression pedal would have been a welcome addition, along with an envelope-following mode.
Where is Intensive Care Audio based?
Intensive Care Audio is based in London, England, where all of its pedals are built by hand using high-quality components. The company was founded in June 2020, and its medical-themed naming was chosen before the COVID pandemic began.
Sources (6)
- VENA CAVA FILTER, Intensive Care Audio
- Intensive Care Audio Vena Cava Filter, Delicious Audio, 2021-11-30
- Guitar Pedal X, Guitar Pedal X, 2023-12-17
- Guitar Pedal X, Guitar Pedal X, 2023-11-03
- Intensive Care Audio VENA CAVA FILTER Distortion v.1, Pedal of the Day (www.pedal-of-the-day.com), 2021-11-08
- Intensive Care Audio Vena Cava Filter review, Guitar.com, 2023-12-04