The Keeley Neutrino, released in 2014, is a pedal that caught many people’s attention as a boutique alternative to the bigger Mu-Tron III envelope filter pedal which started it all back in the 1970s. Why is it so appealing? To start, it’s small and will save space on your pedalboard. Second it sounds excellent and is easier to trigger than other envelope filters. Third, the current re-issue (from Haz Laboratories) is not even the original design by Mike Beigel (creator of Mu-Tron effects). After stopping production of the original Mu-Tron III, he worked with Electro-Harmonix to use his design and create the Q-Tron, which is much closer to the original Mu-Tron III. Read about it here.
Fast forward to the present. In 2014 Mike Beigel released the (now sold-out) Tru-Tron, his newer version of the original Mu-Tron III, for the purists who wanted to get as close to the original design as possible. Trey Anastasio famously took this pedal on the road with the Dead & Company tour. One problem remained: it still took up a lot of pedalboard real estate. This problem, however, helped to create a market for smaller envelope filters inspired by the Mu-Tron III, namely the 3Leaf Audio and Keeley Neutrino, which are arguably the front-runners in the small-box envelope filter market.
The differences are minimal, but we get the sense from recent forum threads that guitarists seem to favor the Neutrino due to it being a little bit easier to trigger the filter effect (especially with single coil guitars). Some also think the Neutrino sounds a bitt fatter than the Proton. Whether this is actually true or not is up for debate and your own testing. There are so many variables with your individual gain structure that your experience may be different.
One thing to consider with any envelope filter is that you need to keep your guitar’s output maxed in order to properly trigger the filter effect. Jerry Garcia, famous for his use of two Mu-Tron III effects with the Grateful Dead, actually had an effects loop running from his actual guitar, before his guitar’s output jack, to ensure that his effects saw maximum gain. He also used a boost in his guitar (Alembic’s Stratoblaster) to help ensure his gain stayed strong through long cable runs to his effects. So, you really need to learn how to play an envelope filter, and how to best incorporate it into your rig.
Comparing the Keeley Neutrino to the Mu-Tron/Tru-Tron Design
This is one of the best videos on YouTube to help you hear how the Keeley Neutrino sounds compared to the original Mu-Tron design…well, it’s actually the newer Tru-Tron from Mike Beigel. Pretty damn close. When you listen to these clips, it’s very clear that in the Low modes, the Neutrino and the Tru-Tron sound nearly identical. Robert and his team did an incredible job getting those classic Mu-Tron tones with the Neutrino.
Putting the Neutrino Through its Paces
This video from Mike Hermans is an excellent resource to help you hear how the Neutrino sounds when played in various applications with various guitars. He does a good job showcasing the quick filter response of the Neutrino, using it with overdrive for more aggressive tones, and of course…getting those classic Jerry Garcia tones.
Isolating the Various Settings of the Neutrino
We produced our own video to help you hear how the Neutrino sounds without any other instruments or effects. Running through the various settings, you can really hear how versatile the Neutrino is. Many guitarists favor the Low Pass settings for those classic 70s Grateful Dead tones, however it is also easily used for more “mainstream funk” tones when using the Band Pass and High Pass settings.
Exploring the Features, Controls & Up & Down Modes
The Neutrino is true bypass, offers a 9V center negative AC power jack and features the following controls on the top of the pedal:
- Selector knob for Low Pass, High Pass or Band Pass
- Selector toggle switch for LO or HI frequency range
- Input Gain Knob
- Peak Knob
For warmer envelop filter tones (ala Jerry Garcia), you’re going to want to focus on the lower frequencies (Low Pass, LO range) and keep the Peak knob around 9:00 – 10:00. As the peak knob is turned up, the filter will “peak’ at a higher frequency and you’ll lose the warmth.
For snappier, edgier and brighter filter tones, experiment with Band Pass and High Pass modes depending on how thin you would like your tone to be. Switching to the HI range allows the filter to stress the higher frequencies.
The Neutrino also comes with a switch on the side of the pedal that allows you to switch between upward filter and downward filter modes. You can hear the tonal differences in the video above. What really stands out to me is that you do not need to change the settings of your pedal when switching between up/down modes. Not all pedals make it this easy, which is especially helpful when playing live.
The Neutrino is a winner if you’re looking for classic 70s envelope filter tones in a small box enclosure. When set early in your pedalboard chain, it can trigger easily due to the addition of the Input Gain knob, and the Neutrino sounds great with light overdrive, fuzz or distortion after it. Too much dirt will result in a loss of the filter effect. The only suggested upgrade that many guitarists would like to see from Robert Keeley in the future is to move the Up / Down switch from the side of the pedal to the top, so it’s easier to switch between modes. Still, at $209, the Neutrino is a great buy.
BONUS: Keeley ME-8 Multi-Echo
While we’re covering the awesomeness of Robert Keeley’s pedals, we’d also like to point out that the ME-8 (Multi-Echo) is an incredible pairing with the Neutrino for creating more spacial envelope filter effects. The ME-8 offers two ADT (double tracking) presets, three delays and three reverbs. All have separate parameters that can be controlled with the knobs. While there’s no videos on YouTube of both pedals together, this review from Mike Hermans showcases the 8 presets of the ME-8. In short, they are:
- ADT Vintage
- ADT Modern
- Tape Delay
- Analog Delay
- Subdivision Digital Delay
- Room Reverb
- Chamber Reverb
- Hall Reverb