In late 1996, I heard the “Setting Sun” radio single (featuring Noel Gallagher) by The Chemical Brothers. The sound was so unexpected and bombastic that it felt like the opening salvo of a pop revolution. My knowledge of synth-based music at that time ran fairly deep, encompassing genres from dance to avant-garde. I had also picked up my first synth from a pawn shop a year earlier, and was on my way to learning the craft. I only knew enough to understand that The Chemical Brothers were onto something new, and I was determined to figure it out. The internet back then was a relatively new resource for the average consumer, so I relied on some traditional detective work. I read the “Setting Sun” liner notes and sat in on speculative conversations at my favorite record store. I also watched for print interviews with The Chemical Brothers and consumed the latest industry rumors circulating at pro audio stores. The consensus was that someone named Sherman was behind the new Chemical Brothers sound. Subsequent releases from Depeche Mode, Björk, and Madonna also seemed to be influenced by that elusive Sherman character. I eventually learned that Sherman manufactured the tool that inspired so many trendsetting artists and urban legends: The Filterbank.
More recently, I heard a few conflicting reports about whether or not the Filterbank was discontinued. The internet had evolved since the late ‘90s, so I resorted to some modern detective work. Both reports were essentially true. In 2017, the Filterbank was replaced by the quieter and more tweakable Filterbank 2. I also uncovered more conjecture about Filterbank 2 than actual credible press. Prevailing opinions suggested that the Filterbank 2 was a bespoke distortion box with filters, but I wondered about its full potential.
That's when I called Sherman founder Herman Gillis. One conversation led to a dozen more as we discussed the Sherman legacy, creating music, and making pizza. I also listened intently to Herman’s recollections of early Filterbank adopters. Along with the artists previously mentioned, or their producers, the list included Tony Visconti [Tape Op #29], Billy Corgan [#115], Lenny Kravitz, King Crimson, Trent Reznor, and many others. The most impressive story is that Herman still personally assembles and tests every Filterbank model in his Belgian workshop.
A week after my first conversation with Herman in early 2025, I unboxed a Filterbank 2 Desktop unit with a serial number just under 11,000. I imagine that Herman could build the Filterbank 2 in his sleep. The retail box included rack ears, but I saw no need to use them because the front panel is already angled. If rack-mounting is preferred, the Filterbank 2 Rack is a 4 rack space enclosure with all I/O jacks on the front panel for convenient integration with a studio patchbay or modular synth. The Filterbank 2 Compact is a tabletop version offered at a slightly lower price.
The new silver/gray finish of the Filterbank 2 looks nicer than the original white and better complements the colorful array of 24 knobs and seven status LEDs on the front panel. This playful aesthetic is somewhat congruent with the artwork in the original Filterbank 1 Abuser’s Manual, now posted online. The back panel includes ample I/O connectors for audio, CV, and MIDI. The Filterbank 2 Desktop weighs 5.5 pounds. Herman chose a heavy steel for the enclosure so it would not likely be affected by gravity when eleven TS cables, five MIDI cables, and a power cable were hanging off the back. The power supply is linear, and the inline design includes a separate power switch on the primary side.
Everything about the Filterbank 2 revolves around its pair of multimode filters. They are LTC1060 integrated circuit chips made by Linear Technologies and were never intended for audio applications. They are officially described as "two high performance, switched capacitor filters." In simple terms, each chip has a clock that pulses to switch filter caps on and off at a rate set by the cutoff frequency. Much of the sonic character associated with these filters is attributable to the leakage of clock noise into the audio path, which is more pronounced with certain filter and envelope settings.
The controls for each filter are identical. The large knobs labeled Freq (1 and 2) set the cutoff frequency. The resonance (Reso) knobs deliver everything from subtle punctuation to partial self-oscillation. The L-B-H knobs determine the filter mode, transitioning seamlessly from low- to band- to high-pass. The mode-correction knobs subtract band-pass on the -B side or also boost low and high frequencies for notch filtering on the -B + LH side. The filters can be routed via a single knob in serial (Ser), parallel (Par), or a blend between the two. Main Out (Output 2) delivers a mono sum of both filters, but using both outputs in either mode will result in lower distortion. In parallel mode, Filter 1 is routed to Output 1, and Filter 2 is routed to Main Out.
Another level of filter control is realized in a harmonic-sync mode. The Freq knobs of each filter operate independently, but the cutoff frequency of Filter 2 can also be synced to a fifth or an octave below the cutoff frequency of Filter 1. When engaging the rotary Harmonics knob, the first position syncs the cutoff frequency of both filters. Higher positions progressively lower the synced cutoff frequency of Filter 2, with a maximum range of four octaves. Harmonic mode tends to boost the output volume, introduce some artifacts, and cause the Freq knobs to become a bit unruly. Dialing them out of their happy place in sync mode may result in a sound like someone dropping the stylus on a vinyl record, with output frequencies below 1 Hz. User discretion advised.
The filters can be wildly animated by several shared modulation sources. The mono input signal must trigger both envelope generators. The ADSR (Attack, Decay, Sustain, and Release) can also be switched to envelope-follower mode. The depth and polarity of ADSR modulation are determined by the Amount knob of each filter. The audio rate LFO can also modulate the cutoff frequency of each filter. Waveform options include triangle, saw, or triangle re-triggered by the AR (VCA) envelope generator. The FM knob adjusts the depth of filter cutoff modulation by the input signal. When FM and Harmonics are engaged, the Track switch enables pitch-tracking of monophonic input signals for a sympathetic filter response that sounds more musical. External modulation sources may be used via the CV inputs.
Before testing the resilience of my studio monitors with the Filterbank 2, I searched for a fader-based MIDI controller to pair with it. The XVI-M from Michigan Synth Works seemed perfect. I contacted company founder Raf Wlodarczyk, who agreed to send me a demo unit. He then informed me that the stock firmware of the XVI-M would not work with the Filterbank 2, but he offered to code custom firmware. That impressed me well before I could appreciate the construction and functionality of the hardware. Although MIDI implementation of the Filterbank 2 is somewhat limited, the 60 mm faders on XVI-M present a familiar interface to beginners and an efficient interface to advanced users.
The sonic adventure began when I plugged my Fender Precision Bass into the Filterbank 2. The envelope generators were not readily triggered by the full output of the passive pickup. I activated Sensitrig mode on the Filterbank 2 and turned the Input knob up into the gain range of creamy overdrive. Then the gates opened. That overdrive sounded excellent on bass guitar. I focused on the filters, FM, and ADSR first. Then I realized that the LFO can approximate effects like tremolo and chorus. After a few hours, I was hooked.
My assistant engineer and I patched in drum tracks from a current project. Kick and snare experiments were each printed on several passes. I kept the modulation minimal, but the stereo width achieved by setting each filter differently in Parallel mode was a revelation. Sometimes I need more than reverbs and delays to fill out sparse arrangements. Drums processed through the Filterbank 2 can add a lot of substance and movement to a mix. In most cases, they function best as accents, background layers, or custom loops.
The specific filter chip used in any subtractive synth will significantly influence its overall sound. The LTC1060 chips in the Filterbank 2 sound like no other synth, standalone filter, or plug-in emulation. Sending raw waveforms and familiar patches from my analog synths through the Filterbank 2 was enlightening. Sounds emerged from the Filterbank 2 with new dimension and a charming bit of lo-fi character. Results were relevant when classic synth patches would not serve the song. I also discovered that the AR may be leveraged as an expander/gate at the output stage to mitigate circuit noise between notes.
The Filterbank 2 can also make something out of nothing. When nothing is connected to the input jack, the Filterbank 2 sources its own internal feedback and noise generator. The tonal variety available in feedback mode is relatively restricted, but it remains useful for creating textural beds, transitional elements, or quirky arpeggios and rhythm patterns driven by the LFO. Half-plugging the cable from Output 1 in this mode will result in lower feedback distortion.
I have no doubt that the Filterbank 2 is an invaluable asset for the production of modern music. It is designed to work well with modular synths, guitar rigs, and hybrid mixing setups. I would not hesitate to use the Filterbank 2 on a Dua Lipa remix, a Spoon [Tape Op #27] album, or a film score. As I explore its full potential further on my future projects, I hope to inspire others as The Chemical Brothers inspired me so many years ago.