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  • Source Audio Mercury Flanger pedal

    By Phil O'Keefe |

    Source Audio Mercury Flanger

    Failure to launch, or out of this flanging world?



    by Phil O'Keefe




    What You Need To Know

    • Part of the Source Audio's flexible One Series, the Mercury Flanger has far more going on than may be apparent at first glance. Housed in an attractive red and black brushed aluminum anodized case that measures 4.5" L x 2.75" W x 2" H, it weighs in at only 280 grams.


    • The pedal is digital, but don't let that dissuade you. With 24 bit converters, 56-bit processing and well-crafted algorithms, it sounds excellent. And, being digital means Source Audio can add loads of capabilities you won't find on analog flanger pedals.


    • The stereo input and output jacks are side mounted. Input impedance is 1 MegaOhm, and output impedance is 600 Ohm, with a maximum output level of +6dBV = 8.2dBu = 2V RMS = 5.6V p-p.




    • The Mercury Flanger is powered by 9VDC via the 2.1mm center-negative power receptacle at the top of the pedal. It draws 180mA, or up to 220mA if used with a Hot Hand controller. Battery power is not an option, but Source Audio includes a regulated power adapter.


    • The top of the pedal is where you'll also find the 1/8" TRS jack for the Control Input signal. A Control Input button right next to the jack configures it for the optional Source Audio expression pedal or Hot Hand controllers. It can also connect to the optional Source Audio Neuro Hub.



    • Third-party expression pedals can also work if they have a TRS plug wired with power on the tip, the wiper of the potentiometer on the ring, and ground on the sleeve. I was able to use a Roland EV5 just fine with a suitable 1/4" TRS to 1/8" TRS adapter.


    • An optional Source Audio Tap Tempo footswitch can also connect to the Control Input jack. When you use an external tap tempo switch, the beat divisions (quarter note, eighth note, eighth note triplet and sixteenth note) are selectable with the Mercury Flanger's Speed knob.


    • The Mercury Flanger also has a USB mini jack. It's class compliant so you won't need drivers for your Mac (OSX 10.7 or later) or PC (Vista or later, including Windows 10) computer. During the course of the review I updated the Mercury Flanger's firmware from version 1.05 to 1.08 using a Mac laptop and the process was easy, fast and went off without a hitch. MIDI is also supported over this USB connection, allowing for DAW control using MIDI clock and continuous controller messages.


    The hardware controls are about what you'd expect to see on a compact flanger pedal.

    • Depth controls the depth of the onboard LFO (low frequency oscillator) and the amount or strength of flanging.


    • Speed adjusts the rate of the Mercury Flanger's LFO and thus the flanger's modulation sweep rate.


    • Resonance (or feedback) can add brighter, more intense tones.


    • Delay sets the delay time. There's enough range here to go from the short delays needed for flanging effects to longer delay times that take you deep into chorusing territory.


    A three-position toggle switch selects among the Mercury Flanger's three main flanging types.

    • Classic takes the incoming dry signal and combines it with a single modulated and delayed version of itself. It's very similar in concept to what a chorus does, except the delay time range tends to be much shorter for flanging.  


    • Thru-Zero is a much harder effect for a pedal to do. It's based on the classic tape flanging studio effect, which requires two tape decks. In the Mercury Flanger, one delay line gives a short, static delay, while another delay provides a modulated delay. As the modulated delay speeds up and slows down it actually sweeps ahead of and then later than the short static delay. When the two reach opposite polarity, they cancel out completely, creating the classic "null" of thru-zero flanging.  


    • Shadow uses two modulated signals for added motion and swirl, with the main flanger sound being accompanied by a "shadow" flanged sound that's subtler and more resonant.


    • There are two multi-function LEDs on top of the Mercury, with the larger one primarily for indicating when the pedal is active. The smaller one nearest to the top is for control-related features, such as showing the tap tempo rate.


    • Switching is what Source Audio calls Universal Bypass. It's set to relay-based true bypass from the factory, and buffered bypass can be user-selected using the Neuro Mobile App.


    • You can store your favorite settings as a preset without requiring any software or other hardware. Simply press and hold the footswitch for five seconds to enter preset mode, set the controls to your liking, then hold the footswitch down again until the bypass LED flashes three times.


    • The optional Neuro Hub (formerly called the Soundblox Hub) and the Hub Manager app (Mac/ Windows) open up the Mercury Flanger's hidden MIDI capabilities. The Neuro Hub allows connecting up to five One Series pedals (or SoundBlox pedals - in any combination), and lets you save and recall up to 128 presets, along with an equal number of multi-pedal scenes that can be recalled with MIDI program change commands. MIDI clock is also supported for tempo-locked effects. Of course you can skip the Neuro Hub and connect your expression pedal directly to the Mercury Flanger if desired.


    • Have an iPhone? You'll definitely want to download the free Neuro Mobile App for iOS. It allows for deep editing of not only the main parameters you can control with the Mercury's knobs, but many more, including output level, lo retain, tremolo, mod source waveform type, channel 2 mix and tremolo invert and LFO offset, tap tempo, parametric EQ and even hardware parameters such as the power-up bypass state I/O routing configuration.



    • Once you have the app downloaded, just plug the included cable into your phone's 1/8" output jack and the other end into Input 2 on the Mercury Flanger. Communication is one direction only (from phone to pedal - the phone can't read the pedal's settings), but it's a easy way to make deep-level adjustments. Source Audio also has a library of different presets available, and an online user's community for sharing presets with other musicians.  


    • The Mercury Flanger isn't just a flanger, but also a chorus and a phase shifter. You can download and use any of the algorithms for the One Series modulation pedals - not only the ones for the Mercury Flanger, but the Gemini Chorus and Lunar Phaser algorithms too. You'll still need more than one pedal if you want to do multi-modulation combinations like chorus with phaser, but if you need different types of modulation but need only one at a time, you won't need to buy three different pedals.



    • As shipped from the factory, the I/O setup may cause some confusion if you're used to more traditional mono in / "stereo" out pedals; you can't just plug your guitar into one of the inputs and have it automatically show up at both outputs. The good news is that you can easily change the routing configuration using the Neuro Mobile App.


    • Mac and PC based editing is not available at this time, although Source Audio has announced that an in-depth effects editor is in the works for both.


    • Again, while one is reportedly in the works, there is also no Android version of the Neuro App currently available.


    • Firmware updates are limited to Mac and PC, and can not be done with your iOS device.


    • You'll need a 1/4" TRS to 1/8" TRS adapter or cable to connect your third-party expression pedal. If your expression pedal has a 1/4" TRS output jack you could use the short cable that Source Audio includes for connecting the Mercury Flanger to your smartphone when editing setting with the Neuro app, but you can only use it for one or the other at a time.



    If you're looking for a compact flanger with a lot of sonic possibilities, that's a fitting description of the Source Audio Mercury Flanger. The free Neuro mobile app gives you much deeper control than the typical flanger pedal offers, and it's easy to use. Kudos to Source Audio for including the necessary 1/8" to 1/4" cable - all you need is a iPhone. Hopefully the Android mobile app and computer editors will be ready soon.


    The Mercury Flanger has a huge amount of features, and supports a bunch more with the addition of options like the Neuro Hub, tap tempo footswitch and expression pedal, but even just firing up the Neuro Mobile App reveals much greater control depth than you'd assume based on the pedal's outward appearance. Of course none of that matters if the sound isn't there, but fear not - flanger fans will love the thick, chewy goodness of the Classic Flange / Chorus, and the Thru-Zero really does null out like it should - and that's a sound that's not available with a lot of pedal flangers. In addition to its three different types of flanger sounds, you can use all of the cool sounds from the Lunar Phaser and Gemini Chorus as well - and all for the price of a single very reasonably-priced pedal. The Mercury Flanger gives you rack-like power and features in easy-to-use pedal form, and at a pedal price point. That's terrific value in my book!






    Source Audio Mercury Flanger ($209 MSRP, $149 "street") 


    Source Audio's product web page    


    Neuro Mobile and Web App web page   


    Optional Neuro Hub information    


    Optional Tap Tempo Switch information    


    Optional Dual Expression pedal information    


    Optional Hot Hand 3 Universal Wireless Effects Controller information    



    Mercury Flanger manual (PDF file)    





    You can purchase the Source Audio Mercury Flanger from:


    Guitar Center    

    Musician's Friend




    One Series modulation pedal demo videos:


    Mercury Flanger




    Lunar Phaser




    Gemini Chorus











    Phil O'Keefe is a multi-instrumentalist, recording engineer / producer and the Senior 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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