ALM Busy Circuits Pip Filter & LFO (2023–)
Two tiny 4HP modules that punch way above their size—raw, characterful, and built for real patching, not just ticking boxes.
Overview
You can fit four of these on a credit card and still have room for a stamp. The ALM Busy Circuits Pip Filter and Pip LFO each take up just 4HP of Eurorack space, but don’t let the size fool you—these aren’t gimmicks or minimalist novelties. They’re functional, no-nonsense circuits built with a distinct sonic character and a refreshingly honest approach to analog design. Released together in 2023 as part of ALM’s ongoing push to deliver compact yet powerful tools for modular synthesis, the pair was clearly designed for builders who value utility without sacrificing musicality. They don’t try to be everything at once. Instead, they do a few things well—and with a bit of grit that feels increasingly rare in a market flooded with pristine, over-engineered modules.
The Pip Filter is a 2-pole voltage-controlled low-pass filter with resonance that goes all the way to self-oscillation. It’s not a 24dB/oct monster like a Moog ladder, nor is it trying to emulate one. Its character is softer, slightly lo-fi, with a warmth that blooms when you push the resonance. What makes it more than just another filter is the inclusion of a built-in VCA and a “ping” input that triggers a short envelope to excite the filter—perfect for plucky, percussive sounds without needing an external envelope generator. It’s the kind of module you patch into a noise source and immediately get something musical, even before you’ve added modulation.
The Pip LFO, meanwhile, is a compact but fully-featured analog oscillator that doubles as a voltage-controlled audio-rate oscillator (VCO) when switched into that mode. It outputs a full suite of waveforms: bipolar and unipolar triangle, sawtooth, sine, and a unipolar square. The manual speed control is smooth and responsive, and the CV input accepts 0–10V for deep modulation. When flipped into VCO mode, it tracks approximately 5 octaves with V/Oct, making it surprisingly usable as a drone or auxiliary oscillator, though it’s not laser-stable across the entire range. It’s not meant to be your main melodic voice, but it can absolutely hold its own in textural patches.
Together, they form a compact signal-processing core. Pair the Pip Filter with the Pip LFO, and you’ve got a complete subtractive synthesis setup in just 8HP. That’s not just space-efficient—it’s conceptually elegant. ALM didn’t pack them with endless features or digital wizardry. They kept it analog, kept it simple, and trusted the circuits to speak for themselves.
Specifications
| Manufacturer | ALM Busy Circuits |
| Production Years | 2023– |
| Original Price | £110 each (UK, including VAT) |
| Format | Eurorack |
| Width | 4HP each |
| Depth | 32mm (approximate) |
| Power | +12V 40mA / -12V 20mA (Pip LFO) |
| Power | +12V 40mA / -12V 20mA (Pip Filter) |
| Filter Type | 2-pole voltage-controlled low-pass with resonance |
| Filter Modes | Low-pass only |
| Resonance | Adjustable to self-oscillation |
| Ping Input | Trigger input to excite filter (with internal envelope) |
| Internal VCA | Yes, integrated into Pip Filter |
| LFO Waveforms | Bipolar triangle, unipolar triangle, sawtooth, sine, unipolar square |
| VCO Mode | Yes, switchable, tracks ~5 octaves with V/Oct |
| Speed Control | Manual knob with CV input (0–10V) |
| Outputs | Multiple waveform outputs (LFO); audio out, CV in, ping in (Filter) |
| Warranty | Two-year warranty |
| Country of Manufacture | England |
Key Features
A Filter That Plays Itself
The Pip Filter’s “ping” function is its secret weapon. Instead of requiring a separate envelope generator to shape transients, it has a built-in response that activates when you send a trigger to the ping input. This isn’t a full ADSR—it’s more like a fast decay that excites the filter’s resonance, creating a percussive “blip” or “pluck” depending on the cutoff and resonance settings. It’s especially effective with noise or a burst of harmonics, turning abstract signals into rhythmic elements instantly. This feature makes the Pip Filter a go-to for experimental percussion, granular textures, or quick sound design sketches where you don’t want to patch five modules just to hear something interesting. The internal VCA means you can feed a continuous source into it and still gate the output via the ping, which is clever and saves space.
LFO That Becomes an Oscillator
Most compact LFOs stay firmly in sub-audio territory, but the Pip LFO breaks that mold with its VCO mode. Flip the switch, and the oscillator jumps into audio rate, tracking V/Oct with reasonable accuracy across about five octaves. It won’t replace a precision digital oscillator, but it’s stable enough for drones, gritty bass pulses, or modulating another filter at audio rates. The waveform selection is generous for a 4HP module—having both bipolar and unipolar triangle and saw outputs adds real patching flexibility. The sine wave is smooth but not perfectly clean; it’s got a slight softness that works well in pads or modulating pitch subtly. The square wave is crisp and useful for clocking or digital-style modulation.
Minimal Footprint, Maximal Utility
At 4HP each, these modules are designed for systems where space is at a premium. But they don’t feel compromised. The panel layout is clean, with clearly labeled jacks and controls that are spaced well enough to avoid crowding, even with larger cables. The knobs are small but have a positive feel, and the switches (especially the VCO mode toggle) are sturdy. They don’t have endless modulation inputs or digital displays, but they don’t need them. Every control serves a purpose, and the signal flow is straightforward. This isn’t a “do everything” module—it’s a “do one thing well” philosophy executed with confidence.
Historical Context
The Pip Filter and Pip LFO arrived in 2023, a time when Eurorack was already saturated with feature-rich, multi-function modules. Many manufacturers were chasing complexity—modules with screens, patch memories, and dozens of modes. ALM took the opposite approach. These modules feel like a quiet rebellion against bloat, echoing the ethos of early modular design where each module had a clear, singular role. They fit alongside classics like the Mutable Instruments Maths or the Intellijel Dual ADSR in spirit—compact, versatile, and deeply musical without needing to be flashy.
They also continue ALM’s reputation for building tools that serve the patch, not the spec sheet. The company’s Pamela’s Pro Workout series had already cemented its place in modular history as a Swiss Army knife of clock manipulation, and the Pip series feels like a spiritual sibling—focused, practical, and built for real-time experimentation. In an era where many new modules are software-defined or FPGA-based, the Pip Filter and LFO stand out by being fully analog, with circuits that have a tactile, slightly unpredictable character. They’re not trying to be perfect. They’re trying to be useful—and interesting.
Competitors in the compact filter space include the Intellijel Steiner-PGA (which offers multimode filtering in 6HP) and the XAOC Belgrad (a 2-pole filter with unique character in 8HP). For LFOs, the ALM units go up against the Doepfer A-145-2 (a basic LFO in 8HP) or the Mutable Instruments Tides (discontinued, but legendary for its smooth waveforms). What the Pip modules offer is a balance: more features than the most basic options, but in a smaller footprint than many alternatives, all while maintaining a distinct sonic flavor.
Collectibility & Value
As of 2026, the Pip Filter and Pip LFO are still in production and readily available from ALM’s web store and authorized dealers. They retail for £110 each in the UK, which translates to roughly $135–$145 USD depending on import fees and exchange rates. Because they’re relatively new and not limited edition, they don’t carry a secondary market premium. Used units, if available, typically sell for 70–85% of the original price, depending on condition and region.
They are not yet “collectible” in the vintage sense—no one is hoarding them for future value—but they are becoming staples in minimalist and travel-sized systems. Their build quality is solid, with no widespread reports of reliability issues. The PCBs are well-designed, and the components are standard through-hole types, making repairs feasible for technicians familiar with Eurorack servicing. The main point of failure would likely be the power connector or input jacks due to mechanical stress, but there are no known design flaws like failing capacitors or oscillator drift.
For buyers, the biggest consideration is authenticity. Because ALM sells directly and through a limited number of trusted dealers, units purchased from third-party marketplaces should be checked for original packaging, firmware version (if applicable), and signs of modding or damage. The modules do not have firmware updates in the traditional sense, but documentation and schematics are available on the ALM website, which helps with verification and repair.
These aren’t modules that will appreciate in value, but they also aren’t likely to become obsolete. Their analog nature, simple design, and utility ensure they’ll remain relevant for years, especially in starter systems or as utility tools in larger racks. If you’re building a compact rig or need a backup filter/LFO that doesn’t eat space, they’re a smart investment.
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