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Dual channel overdrive / boost pedal with amp-like even-order harmonic overtones


$449 list, $399 "street"




By Phil O'Keefe



While the Alairex name may be new, company founder Alex Aguilar is no stranger to musical electronics and technology, having co-founded Aguilar Amplification and having served as their head design engineer. His name may also be familiar to many readers who remember his long-running "Amp Questions and Answers" monthly column in Guitar for the Practicing Musician magazine. With Alairex, Alex is now turning his attention and considerable talents to guitar specific products, the first of which is the HALO overdrive (Figure 1) under review here.





Figure 1: The Alairex HALO overdrive (click on image to enlarge)




HALO stands for "Harmonic Amp-Like Overdrive," which is actually a fairly good description of what the pedal does: place emphasis on second and even-order harmonics in the distortion. The sound of even-order harmonics is often described with terms like "sweet," "warm" and "fat," and is often associated with tube amplifiers. According to Alairex, the HALO was designed to be a fundamental component of a player's sound, allowing them to "take their sound with them" in situations where the player has to use whatever backline amps that are provided by the venue.


The HALO is actually two overdrives in one, each with separate gain and level controls. While both are capable of the same basic range of sounds - from clean to quite saturated, the player can easily dial up two different overdrive sounds, each with different amounts of distortion (gain) and output level, and then switch between them at will with the HALO's second footswitch. A blue LED that corresponds to the left footswitch indicates when the pedal is active, and on the second footswitch, a dual color LED indicates which of the two channels is active - yellow for Gain 1 and red for Gain 2. While both channels cover similar sonic territory, Gain 2 seems to have a bit more drive, even with identical gain and level settings dialed up on both channels.


In between the dual gain and level knobs, you'll find the Tone knob. This is a treble boost / cut control that sets the overall tonal character and brightness of the pedal, and it affects both gain channels. This control offers a considerable amount of range, and unlike similar controls on some pedals, useful tones can be found throughout the control's range and not just in one or two "sweet spots." However, the tone controls don't stop with the single Tone knob. Three smaller knobs are situated above the five main knobs, and these also provide additional tonal shaping capabilities. The Bass knob controls the amount of bottom end, and is centered at 100Hz. The Presence control dials up the upper midrange content, with the sound becoming more detailed as you turn it up. The Contour knob controls the midrange. Turning this control down results in a "scooped midrange" that brought to mind classic Fender Blackface era tones, while cranking it up results in more present and aggressive mids that reminded me more of classic Tweed era amps.


The overdrive character can be further adjusted with the "Shape" toggle switch. This allows you to set the pedal for symmetrical or asymmetrical clipping, or for clean boost. In clean boost mode, up to 17dB of gain is available, and the tone is less harmonically complex and compressed; similar to some high-end "transparent overdrive" and clean boost pedals. The symmetrical clipping mode is brighter and thicker than the clean boost mode, while the asymmetrical mode is the darkest, heaviest and most harmonically complex of the three. The ability to change the type of clipping adds considerably to the versatility of the pedal.


The second toggle switch (labeled "Saturation") adds in an additional post-gain control gain stage, resulting in a more distorted and compressed sound. The Saturation switch allows you to apply this extra gain to both channels, channel 2 (Gain 2) only, or to turn it off entirely. When engaged, it gives the sound a "singing sustain" that reminds me of some of the best cascading gain stage amplifier designs in its overall tone.


There are lots of nice little touches that show just how much thought went into the design of this pedal. The housing is made of heavy gauge steel and is nicely finished. The front panel graphics, while being somewhat reminiscent of an old Wehrmacht emblem, are protected beneath what appears to be a clear Lexan plate that covers nearly the entire top of the pedal. Actually, the logo was probably inspired by Alex Aguilar's last name, which can be roughly translated as "eagle's lair." Another nice touch is the way that the blue active / bypassed LED will dim as the battery voltage drops. Once it goes below 7 volts, the LED will no longer illuminate, so you'll know when it's time to change the battery. The battery is switched off whenever the input jack is unplugged. The pedal can be powered by a standard 9V battery, which is accessed through a tool-free sliding "drawer" on the top of the pedal. The standard 5.5mm x 2.1mm center-negative power jack is also located at the top of the pedal, and will accept any DC voltage from 9 to 18 volts. The pedal sounds fine at 9V, but you'll notice increased headroom at higher voltages. The rubber "feet" of the pedal have integral metal bolts that hold the bottom of the pedal in place, which allows you to open the pedal up without the use of any tools (Figure 2), although you'll probably never need to since the battery can be easily accessed without disassembly and there are no additional controls or trim pots located inside. The solid-state switching is reliable, and the low impedance buffered output is capable of driving long cable runs without excessive noise or signal loss. The input is high impedance, so you don't need to worry about it loading down your pickups.



HALO gutshot.jpg


Figure 2: The interior of the HALO, showing the clean construction and wiring. Also note the design of the feet that hold the bottom plate in place





The HALO has a sound that is both unique and yet familiar; while it has a tone that brings to mind the sound of a nice all-tube amp, I've never heard another overdrive pedal quite like it in terms of its clarity. Individual notes, even in harmonically complex chords, are easily distinguishable, and the note definition is excellent. Additionally, the tone is far from static. Hit a big power chord with a lot of gain dialed up, and the sound and overtone content changes and evolves; from the slight "sag" of the initial attack, through the bloom and sustain, and as it eventually decays. The tone is chewy and thick, but without mud or woofiness, and the tone controls give you a ton of useful timbres. Depending on the settings of the Saturation switch and Gain knobs, you can get a wide range of different overdriven tones from this pedal, and all of them are very amp-like in their dynamic response, with some of the same sag and touch sensitivity that you would expect from a great tube amp, and a tone that is very reminiscent of one. This isn't a pedal that "covers" the sound of your guitar; it enhances it. While the price may be a bit off-putting to some, when you consider the versatility and the fact that it can take the place of two overdrive pedals of exceptional quality, it starts to make a lot more sense. This is a highly expressive, first-rate overdrive that will impress those who appreciate great tone, and who seek a pedal that responds to the nuances of the player's touch. This is an excellent first release from Alairex. I look forward to hearing what they come up with next!





Phil\\_OKeefe HC Bio Image.jpg




Phil O'Keefe is a multi-instrumentalist, recording engineer / producer and the Associate Editor of Harmony Central. He has engineered, produced and performed on countless recording sessions in a diverse range of styles, with artists such as Alien Ant Farm, Jules Day, Voodoo Glow Skulls, John McGill, Michael Knott and Alexa's Wish. He is a former featured monthly columnist for EQ magazine, and his articles and product reviews have also appeared in Keyboard, Electronic Musician and Guitar Player magazines

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