A pedal for your pedals! New from Great Eastern FX is the XO Variable Crossover, a pedal that will surely spark creativity in your signal chain. The XO gives the user the ability to split the input signal into two frequency bands, high and low, and then process those bands separately through dedicated effects loops. For example, imagine sending high frequencies to a distortion, octave‑up pitch‑shifter and reverb, while the low frequencies are sending separately to a tremolo and delay, each signal path essentially unaffected by the other because they are running in parallel.
Technical features of the XO begin at the main control knob, which determines the frequency where the high and low bands cross over, and it’s clearly labelled ‘crossover frequency’. The high‑ and low‑pass filters have 12dB/octave slopes, and the overall frequency range can be changed from 50‑600 Hz (bass range) and 300Hz‑3.4kHz (guitar range). The polarity of the low send can be inverted, resulting in a phase cancellation in the area where the frequencies overlap. The high and low sends can also very easily be flipped with a switch on the pedal, to avoid the need to unplug and repatch your pedals. This allows the user to hear instantly what the low band effects chain might sound like on the high band, and vice versa.
The creative expansiveness that this pedal makes possible is only limited by one’s imagination. This is the beauty of a relatively simple tool that’s come onto the market at a time when many effects themselves have become so complex. A crossover is nothing new to recording studios, live sound engineers or the hi‑fi audio world. But in this format it can easily interface with guitar effects, looping devices, multiple amplifier setups and more. The XO gives the user a chance to connect pedals they’ve used for years and discover something fresh with them. Take two effects as old as time: distortion and delay. Patching the distortion to the low bands and delay to the high bands and using a guitar as the main source, the lower notes will be distorted and the upper frequencies will be clean and delayed. Want to swap that around? Just press the swap button.
The XO’s crossover comprises a pair of filters that allow you to route only the low frequencies to one effects loop, and only the high frequencies to another — but there are some lovely additional touches here that open up many more possibilities than band splitting alone.
Speaking of new sounds from old devices, using separate distortion/fuzz/overdrive pedals for high and low frequencies is possible now. For example, a Big Muff fuzz for the lows and an Octavia or Green Ringer type pedal for the highs, while adjusting the balance and crossover knobs to get it just right. You can now dial in a sound that previously would have been a major hassle, or just not possible at all before the XO.
But even without other pedals, the XO can be used as a tilt EQ, splitter, mixer or buffer/line driver. As a splitter, it can be placed at the end of a pedal chain and send highs to one amp, lows to another, and even have different pedals going to each amp. When using the sends, balancing the effects with the dry signal is straightforward using the Dry Blend knob, while the mix of the high and low effects is controlled by a Return Balance.
When I first discovered the Electrix Mo‑FX, the most interesting part to me was its network of filters. Unlike with the XO, you’re limited to the onboard effects, but what I took away from it, just from its ability to process frequency bands separately, was how quickly I came up with new ideas and new textures just with a delay and tremolo. For example, the low end of my guitar was sent to a deep, pulsing tremolo effect and the top strings to a panning delay. The XO expands on this, by allowing the user to connect any of their own effects and processors.
You can now dial in a sound that previously would have been a major hassle, or just not possible at all.
To illustrate just the sort of thing you can do with the XO, it’s probably helpful if I describe some favourite setups that I discovered during the review period. They all use a guitar as the main source. The first — let’s call it Chain 1 — has a Digitech Space Station (Preset 3, ‘String Swell 4ths’) on the high band and both a Boss OC‑2 and a delay on the low band, with both bands processed through a reverb. Chain 2 put a delay with long feedback on the high band, and on the low band a Moog Ring Mod, with a square‑wave LFO slowly modulating an interval of a fifth. Finally, Chain 3’s high band is treated to a long (around 8s) delay line with Expedition Electronics’ 60 Second Delay, with the effect mix at 100% with no dry signal. The low band, meanwhile, has a continuously recording loop with an Eventide TimeFactor, the effect mix again at 100% with no dry signal. With the Dry Blend set to 0 on the XO, each band doesn’t return to the XO but connects in stereo into a Lexicon LXP‑5 set to a randomised panning delay. This makes for a beautiful texture of different frequency bands bouncing across the stereo image creating a long, ever‑changing ambient soundscape.
As I said, those were just what I stumbled upon with a guitar. And given the pedal format, one might assume it’s intended only for guitarists — but the XO stretches way beyond that. This pedal will not only find its way on to pedalboards but should also become a staple in every studio’s pedal collection. I can envision the XO becoming ubiquitous amongst sonic explorers, engineers and producers alike. The XO opens the door to new sonic possibilities that were previously unavailable in such a user‑friendly format.