Zorx Electronics
​  FIL4 Timbral Sculptor - Future Sound Systems

​ FIL4 Timbral Sculptor - Future Sound Systems

by Ian Rapp

Future Sound System’s FIL4 Timbral Sculptor is one of those modules with stacked functions that give it a unique footprint. It’s not just what’s inside, but how everything can be routed, intertwined. In this case, it’s a module broken up into three parts; a multi-mode FILTER, a VCA, and a TIMBRE section; however, thinking of the FIL4 in such basic ways really belies all it brings to the table. The FILTER section sports a three-pole 18dB/oct filter that can self-resonate when the RESONANCE is pushed hard and can track pretty well. There’s also an AUDIO FM attenuverting control, which is inspired by the filter on the Korg35 chip that was the crux of the beloved MS-10 and early production MS-20 filters [later models switched to an OTA], with its ability to sound aggressive. Does it work? Can the FIL4 sound aggressive? Hellz yeah it can. There’s also a Lockhart wavefolder in the resonance path to further warp your sound. If you’re not familiar with a Lockhart wavefolder, don’t distress; neither was I. It was designed by R. Lockhart Jr. who published the circuit design in the 70s and has been utilized by a few notable DIYers [namely Ken Stone] in various designs. Now that we have the small bit of synth design history out of the way we can talk about wave rectification. Why? Well, because the FIL4 has a rectification toggle to switch between half-wave rectification [HWR] and full-wave [FWR] to give more sonic options. I love the idea of rectification as it gets rid of that pesky negative voltage. There’s already too much negativity in the world, right? Anyway, it’s an interesting way to manipulate your sound especially in relation to how the RESONANCE behaves.

One of the really cool things they’ve done with FIL4 is to give control over each of the three filter states; lowpass, high pass, and band pass with CV input and attenuator control of each VCA that’s tied to it. There’s also CV input and attenuverting control over RESONANCE and FREQUENCY, which has two inputs for more mass destruction.
The TIMBRE section is a West-Coast inspired wavefolder, which contrasts nicely with the East-Coast style FILTER section. It seems we can all get along, and the FIL4 proves this by not only housing these two [non] opposing ideologies, but by using them to great effect. There are a couple of unique aspects to this circuit as exemplified by the PRE/POST toggle which lets you assign where in the signal chain the TIMBRE section effects. If it’s working the PRE, there’s a DRIVE control to push the waveform into crunchy territory. If the TIMBRE section is working in the POST setting, it affects each of the three filter band’s VCAs, and it’s here where the DRIVE does the most damage, creating more harmonically rich textures the more you push it. Just flipping the PRE/POST switch into POST sent my signals into a frenzy, especially when modulation was patched into each of the three band’s CV inputs. Set up like this and I got some pretty interesting modulation and spectral changes with some rhythmic irregularities [mostly coming from a random LFO into the HP CV in].
The final section is the VCA that can be used separately from the rest of FIL4, but can also be placed in front of or at the end of your signal, which is where it creates its magic.
With the three outputs–VCA, CHAIN OUT, and TIMBRE OUT–FIL4 also gives you a few related [or unrelated if the VCA is working independently] mixing options to do with what you want of your sound.
FIL4 is a really fun module with some great routing possibilities that set it apart from similar synth voice modules. While that last sentence might not sound super enticing, in real world practice it’s very enticing. Once I had FIL4 all patched up with every CV receiving voltages and the outputs routed to various effects and my mixer, it was off to the races. While I changed my inputs, trying out snare, full drums, bass lines, some ambient patches, and altered the rates of modulation to see what’s what, I was impressed with the variation of sound I was able to get from just using the one module and some LFOs. To be fair, there were plenty of times when I was just wildly twisting knobs, unsure of how FIL4 was going to respond, especially so when I got out of a basic input/output mode and had the CV all patched up, but even just using the filter with the DRIVE and AUDIO FM, the sound sculpting was impressive. You do need to find the sweet spots as there were times that twisting one parameter put another out of its sweet spot, sometimes drastically changing the sound. I also suggest that if you get a tone/sound you like, you best hit record because it’s not the type of module that’s easy to recall any sounds on and you know…there ain’t no presets on FIL4.
It helps to check out the signal diagram that’s included in the manual as it gives a good visual of the signal entry points and how the VCA can be routed, etc. One thing I found confusing is that the FREQ CV1 input doesn’t have any onboard attenuation, but FREQ CV2 does. This is slightly confusing because, while there is no control labeled “CV1,” there is a “CV” control under the RESONANCE used to dial in the CV for the RESONANCE control when there is some patched in, which I kept thinking was the attenuator for CV1. It’s not.
This is a great, versatile module that combines additive and subtractive synthesis techniques under one faceplate [who’d a thought?!], one that’s going to get a ton of use in my rig. I totally dig the filter sound without even much else going on, and the DRIVE and AUDIO FM add so much along with the ability to control each of the filter’s bands... From 8-bit arcade sounds, to additive grunge blasphemy, to warped laser guns, to bongo blips, there’s a ton of fun to be had with FIL4.

16 HP +12v 130mA -12v 110mA
Price: $339