analog preamp pedal Walrus Audio Mantle Bass Pre-Amp & DI

The Mantle is a premium preamp and DI for electric bass, created in close collaboration with Ian Martin Allison. Designed to give your instrument an impeccable sonic foundation, the Mantle brings studio-grade refinement to any environment - whether you’re stepping onstage, tracking in the studio, or shaping your tone at home. 

At the heart of the circuit are our proprietary, custom-wound Sapphire Transformers, engineered to deliver the authoritative low-end and midrange push reminiscent of a classic Neve circuit, paired with an airy, articulate top end inspired by revered API preamp architecture. Together, they provide a harmonically rich canvas that elevates your playing while preserving every nuance of your instrument. 

The Mantle empowers you to sculpt your signal with intention, offering musical gain, smartly tuned EQ, tremendous headroom, and transformer-balanced outputs. Every component and stage of the signal path is built to ensure whatever comes next - amp, interface, or mixer - receives your bass in its most confident, fully realized form. 

“I am an absolute DI fanatic, owning probably 50+ DIs and preamps. And while they’re all great in specific ways, they all either lack something critical or try to stuff in too many features, making for an underwhelming or even overwhelming user experience! This is exactly why I wanted to make Mantle. I needed this product to exist. I’m thrilled to say that now it does. And it is absolutely killer.”  

                                                                                                                   -Ian Martin Allison

 Features 

 Signal Path Overview 

Input → JFET Buffer → Low-Pass/High-Pass Filters or Dry Path → Input Transformer (-6dB to +23dB) → Boost EQ → Output Transformer

 
The Mantle’s architecture is meticulously voiced to maintain clarity, delivering musical transformer coloration, and giving you control over both the front end and final output of your tone. 

Transformers 

The Mantle features our proprietary custom-wound Sapphire Transformers. With more than a year of research, listening, and refinement, the Walrus engineering team has set a new benchmark for their designs with new input and output transformers reflecting our commitment to providing creators with cutting-edge tools that inspire innovation and creativity. 

Based on Neve designs, the input transformer is capable of handling large signals without added distortion while maintaining a clean, strong, and quiet signal. High-quality core material and copper windings were used to achieve the gain needed for pristine performance across the frequency spectrum. 

The output transformer is based on the output stage of an API 312. This serves two functions: It balances the signal quietly and effectively while also providing rich harmonic content to the amplified signal. Like the input transformer, the style of core and customized winding method result in a strong signal that can be transmitted over long cable runs without signal loss. 

Connections 

Controls 

Bass & Treble (Boost/Cut Filter System) 

The Mantle’s EQ is a sophisticated dual-behavior design, far more expressive than standard shelves. Both Bass and Treble controls feature eleven-position rotary switches for a satisfying studio feel, easily reproducible settings, and a true flat response at noon (position 6). 

Boosting (positions 7–11): 

Cutting (positions 5–1): 

This design allows precision mix shaping or broad musical coloration, without sacrificing elegance or fidelity. 

Gain Control 

The Gain control adjusts the amount of transformer-based gain applied to the signal. The gain circuit comes directly from the input transformer, creating magnetic manipulation at its finest. This control offers a gain range from -6dB to +23dB across the control range. 

With the combination of the JFET buffer and transformer gain, the result is a tone that feels alive, dimensional, and deeply expressive. 

Switches 

Active / Passive (-10dB Pad) 

Ground Lift 

FAQ 

Q: Can I run this as my always-on tone solution? 
Yes. The Mantle is designed to function as your primary front-end, studio-quality, always-on preamp and tone-enhancer.  

Q: Can I use both 1/4” and XLR outputs at once? 
Absolutely. You can send the 1/4” to an amp onstage and the XLR to FOH simultaneously. 

Q: Does it take other pedals well? 
Yes. The high-headroom JFET front end and transformer-driven architecture preserve clarity and cohesion even with compressors, drives, and modulation feeding into it. 

Specs