The Fundamental Fuzz is Walrus Audio’s entry into Big Muff territory: simple, aggressive, and immediately obvious about what it is. After plugging in, it’s pretty clear you’re dealing with some kind of Muff variant. Just from the sound and feel, I have a hunch it could be op-amp based like the Smashing Pumpkins-era recordings, but I could be wrong. What’s not in doubt is how easy it is to get a great fuzz sound out of it fast.
Like with the whole Fundamental Series, the control choices are well judged. The faders snap in the middle, which makes you think that this is the intended sweet spot from the builder. Three sliders and a three-way mode switch cover a lot of ground without overwhelming you.
The panel runs top to bottom: Gain, Tone, Volume, then the three-way mode switch below those. Gain sets the amount of distortion applied to the signal; Tone shapes the frequency response after distortion; Volume sets your output level. The mode switch is where the character changes happen. In the demo above I’ve set up sweeps for Gain, Tone, and the Mode switch, so you can hear each control doing its thing across the full range.
The three presets in the demo map the personality of each mode. Classic Muff (Gain at 9, Tone at center, mode set to Classic) delivers Walrus Audio’s description to the letter: screaming fuzz with a mid scoop, compressed and crunchy. Spitty Velcro (Gain maxed, Tone center, mode set to Gate) uses the gated mode, which lowers the bias voltage for a starved, spitting character that cuts out tight instead of blooming into sustain. Mids, Baby! (Gain at 5, Tone center, mode at Mid+) is the outlier: the mid boost flattens out the tone stage and the fuzz pushes forward rather than sitting back in the mix.
Especially in the context of a backing track, the difference is obvious. Gate and Classic modes blend into the mix, while Mid+ jumps forward. All three presets in the demo are normalized to the same peak loudness, so you’re hearing tonal character rather than volume differences.
The EHX Big Muff NYC is the logical comparison since both pedals share the same lineage. The classic Muff gives you one voice that you dial in and commit to; its scooped mids and singing sustain are the template everything here is measured against. The Fundamental Fuzz takes that same starting point and adds two variations: the gated mode for a tighter, more aggressive character, and the Mid+ mode that effectively un-scoops the midrange and pushes the fuzz out front. If the Muff’s classic scooped roar is exactly what you want, the EHX version has it in purer form. If you want that sound plus the option to gate it down or boost the mids without buying a second pedal, the Fundamental Fuzz covers more ground for the same footprint. I also used the Fundamental Fuzz in Classic mode on bass together with some EQ from the MAE Line Blur and it sounds massive and punchy, which isn’t always a given with Muff-style circuits.
This pedal suits players who want a no-fuss Muff-style fuzz with a bit of flexibility baked in. The gated mode is always welcome for tighter, more articulate riffs; the mid-boost mode works well in dense mixes where a standard scooped fuzz disappears. It’s part of the Walrus Audio Fundamental Series, so it pairs naturally with the rest of that lineup. I used the Delay, Phaser, Fuzz and Reverb from the Fundamental Series together to record guitar overdubs and lead lines for the backing track in the demo. If you need a Muff that covers the classic scooped sound and also lets you cut through a band mix without swapping pedals, this one earns its spot. If your ideal fuzz is a looser germanium or silicon Fuzz Face character rather than a Muff, look elsewhere.
Discover the essential guitar pedals that define stoner rock, from classic Big Muff fuzz to QOTSA-approved overdrives. Complete guide with ...
A series of Big Muff reissues that pretty much covers all the highlights of EHX's history of Big Muffs. And ...
A shootout of six different Big Muff-style fuzz pedals. The Electro Harmonix Big Muff PI USA, JPTR FX Warlow, MAE ...
More pedals, more fun 
Buy now, brag later Buy through these links and support Loopy Demos at no extra cost to you.
Get detailed specs on Walrus Audio's website
<div data-loopydemos="walrus-audio-fundamental-fuzz" data-title="Walrus Audio Fundamental Fuzz | Loopy Demos" data-width="400" data-height="610"></div>
<script src="https://loopydemos.com/embed.js" async></script>To embed this demo on your website, copy & paste the code above or customize your demo widget