2HP COMB (2015–)

Name: 2HP COMB
Brand: 2HP

A sliver of metal that turns noise into strings, speech into ghosts, and sine waves into something alive - like a tuning fork dipped in mercury.

Overview

The 2HP COMB is easy to recognize by ear. It doesn't blend in. Put this 2HP module in any Eurorack system and it adds a voice with harmonic ghosts and metallic resonance. It's not a filter in the traditional sense. It doesn't smooth or muffle. It carves teeth into whatever passes through, a ladder of evenly spaced frequency peaks that can shimmer gently or vibrate hard, depending on how far you push it. At low resonance, it's a phaser's introspective cousin - subtle, spatial, coloring without dominating. Crank the resonance and sweep the frequency, and it becomes a singing saw, a theremin lost in a metal warehouse, a voice speaking through a fan.

Tony Rolando of 2HP designed it, and it fits the label's minimalist approach. It does one thing - comb filtering via an infinite impulse response (IIR) topology - and does it precisely and musically. Many comb filters sit in the background as texture tools. This one demands attention. It tracks 1V/oct, which is rare in this category, so you can play it like a melodic instrument, not just modulate it. Feed it a saw wave, sweep the cutoff with a slow LFO, and you get a pad that breathes. Run white noise through it, and with the right dampening and feedback, it gets uncannily close to a bowed string section. Thin, yes, but haunting.

The feedback path includes a dampening filter, and that is the key to the module. Without it, high resonance settings would collapse into harsh, chaotic oscillation. With it, the module stays musical even at self-oscillation, which it reaches cleanly and predictably. The dampening smooths the peaks and tames the upper harmonics just enough to keep things from turning brittle. The feedback is internal and voltage-controllable (via the resonance CV input), so you can modulate the character of the resonance itself, not just its intensity. Most comb filters don't offer that.

Specifications

Manufacturer	2HP
Production Years	2015–
Original Price	$119
Width	2HP
Depth	45mm
Power Consumption (+12V)	87mA
Power Consumption (-12V)	28mA
Power Consumption (+5V)	0mA
Filter Type	IIR peaking comb filter
Self Oscillation	Yes
CV Inputs	Frequency CV, Resonance CV
Audio Inputs	Audio In
Audio Outputs	Audio Out
1V/oct Tracking	Yes
Feedback Path	Internal with dampening filter
Topology	Infinite Impulse Response (IIR)
Controls	Frequency knob, Resonance knob
Panel Options	Silver, Black
Manual Availability	Available online

Key Features

The Narrowest Path to Rich Resonance

At just 2HP wide, the COMB is one of the most space-efficient resonant filters in Eurorack. That changes how you use it. You don't need to set aside real estate for it like you would for a Serge Resonant EQ or a Mutable Instruments Peaks. It fits in the leftover inches and the skiff corners. Small doesn't mean simple, though. Its IIR topology gives it a smoother, more analog character than many digital comb filters, which can sound cold or clinical. The frequency knob has a wide sweep, and because it tracks 1V/oct, you can patch it into a sequencer and play melodies that sound like tuning forks struck in sequence. It's not a full synth voice, but in a sparse patch it can carry a melody with eerie clarity.

Resonance That Sings, Not Screams

Most comb filters either sit quietly in the background or collapse into feedback chaos when pushed. The COMB's resonance control goes all the way to self-oscillation, but thanks to the dampening filter in the feedback loop, it doesn't turn into a digital screech. It sings - pure sine-like tones that can be modulated, bent, and shaped. That makes it useful as a secondary oscillator. Patch it into a feedback loop with a slight delay, modulate the frequency with an LFO, and you get a drone that evolves for minutes without repeating. The resonance CV input is exponential, so it responds musically to control voltages, not linearly like some utilitarian modules. Use envelopes or random voltages to swell the resonance in expressive, non-mechanical ways.

Feedback Dampening: The Hidden Architect

Without the dampening filter in the feedback path, high resonance settings would emphasize upper harmonics to the point of harshness. With it, the module keeps a warm, rounded character even at extreme settings. The dampening smooths the harmonic ladder, making the peaks less piercing and more tonal. That's why the COMB can convincingly mimic string ensembles or vocal formants from noise. It also works well on drums: a snare hit through the COMB, with resonance modulated by the envelope, can sound like a resonant chamber or a metallic echo. This feature is rarely discussed in reviews, but owners quickly realize it's the reason the module doesn't fatigue the ears.

Historical Context

The 2HP COMB arrived in 2015, right as Eurorack was shifting from boutique curiosity to mainstream synth culture. At the time, most filter modules were either analog classics (Moog-style ladder, state-variable) or digital powerhouses (like those from Make Noise or Intellijel). Comb filters existed, but they were often tucked into multi-function modules or digital effects units. A dedicated, skiff-friendly comb filter that tracked 1V/oct was practically unheard of. It wasn't trying to be a Swiss Army knife - it was a scalpel.

Tony Rolando, the mind behind 2HP, had already built a reputation for minimalist, high-impact designs like the Loquelic Iteritas and the Z-DSP-based modules. The COMB continued that philosophy: do one thing, do it well, take up no space. It arrived alongside other compact modules like the ALM 0-Coast and the Noise Engineering Loquelic Iteritas Perc, but it focused on a single, under-explored sonic niche. Competitors like the Mutable Instruments Clouds offered comb filtering as part of a larger granular engine, but nothing matched the COMB's immediacy and focus. It was, and remains, the go-to module for anyone who wants comb filtering without clutter.

Collectibility & Value

The 2HP COMB has never been rare in the traditional sense. It's been in continuous production since 2015, and 2HP has maintained steady availability. It still isn't common on the used market, because people buy it and keep it. Original MSRP was $119, and it still sells new at that price, making it one of the best value-to-impact ratios in Eurorack. On the used market, expect to pay $80 - $100 depending on condition and color. Black panels sometimes fetch a dollar or two more, but not significantly. There are no known production runs or variants that drive collector prices, and no firmware revisions to track.

Failures are uncommon. The module has no moving parts, no complex ICs beyond the core filter chip, and draws modest current. Service technicians observe that the most common issue is cosmetic - scratched or oxidized front panels, especially on older silver units. There are no known design flaws or failure-prone components. Because it's a passive filter with no audio output stage, it won't damage other modules if it fails. Still, always check for 1V/oct tracking accuracy when buying used. Some early units reportedly had slight tracking drift at the extremes, though this is rare and usually correctable with calibration if the design allows.

For buyers, the real question isn't reliability, it's utility. The COMB isn't a "must-have" for everyone. If you're building a first system and need oscillators, filters, and envelopes, this isn't the place to start. If you've got a solid foundation and want to add unique texture, it's a no-brainer.