The envelope filter is a crucial element for Bringing The Funk (a task so important it must always be capitalised). Loosely defined as “kinda like a wah wah but not quite, and also it’s automatic,” a typical envelope filter might consist of two controls: one to select the range of the effect and one to set the point at which your picking will trigger it. Aguilar knows bass players, and they know bass effects – just witness the incredible Octamizer octave divider some time to see what I mean – so when they turn their attention to the envelope filter with special emphasis on bass players, you’d better listen.

Structurally, the Filter Twin shares a few traits in common with the Octamizer (as well as the Agro Bass Overdrive and the TLC Compressor). All four pedals are housed in a heavy, solid rectangular case with a handy slide-out battery door accessible via the bottom, four rubberised knobs at the top, a bright blue status LED (which can light up a dark room) and a heartily stompable footswitch. The input, output and 9 volt adaptor jacks are at the top of each unit, making them very pedalboard-friendly. The Filter Twin’s finish is surf green with a solid black outline, giving it an almost ’1950s appliance’ kind of vibe. I love stuff like that.

As hinted by its name, the Filter Twin actually includes two envelope filters. One cycles up and the other cycles down, triggered by the dynamics of your playing. Semiotics buffs will nod knowingly at the layout and labelling of the controls. These controls are Blend (flanked by an up arrow on the left of the knob and a down arrow on the right), Threshold, Velocity Down (actually just labelled Velocity, followed by a down arrow) and Velocity Up (ditto). The knobs feel ‘set-and-forget,’ meaning you need to expend a decent amount of finger energy to get them to turn. I really like this because it means you can be confident that your settings will remain in place even if a crowd surfer crashes onto your pedalboard. That’s very important with a pedal like this where the circuitry is dependent on the output of the signal sent to it by your instrument. Once you nail the sweet spot on the Threshold control, it’s best that you stick to it.

The Filter Twin’s sounds have a real depth and life to them – a rubbery slinkiness which works perfectly with slap and pop techniques and is also good for other picking options. Use the Threshold control to dial in the point at which the effect engages, then twiddle the Velocity pots to select how quickly each filter moves. Blend varies the ratio between each, from 100% of one and zero of the other to a nice 50:50 balance and any point in between. I’m a sucker for really bassy, backwards envelope filter sounds, and unfortunately my main envelope filter – a DOD FX25 – doesn’t have this feature (though it is included in a multi effects unit I use sometimes), so I relished the opportunity to set up a nice 75:25 blend of down and up filters with long down velocity and quick up velocity for a big, syrupy, bassy sound with just the right amount of top end too. The ability to tweak the length of the effect means you can get some pretty interesting sounds as the two filters move against each other, from a snappy quack to a slow, sonorous roar.

By the way, the Filter Twin also sounds great through distortion and on guitar. I ran my bass into the Filter Twin then a fuzz unit and was blown away by the wah-like harmonic richness of the down filter, while it tracked great when I introduced it to my 7-string Ibanez Universe.

The Filter Twin is a killer addition to the arsenal of any funk player but it also sounds great for a variety of other styles, from rock to dance (and could also be a very ear-catching effect for metal bass players in a similar way to how Cliff Burton used wah wah in For Whom The Bell Tolls). It’s also extremely roadworthy and feels like it will give you decades of unwavering service.

LINK: aguilaramp.com

This is an alternate version of a review I originally wrote for Mixdown magazine.