Walrus Audio Mantle Bass Preamp and DI - Black

Refined Tone Foundation – The Walrus Audio Mantle Bass Preamp and 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.

• High-impedance JFET input buffer for articulate, touch-sensitive response and exceptional clarity
• Up to +23dB of transformer-based gain offering clean, magnetic, harmonically rich amplification with premium depth and detail
• Custom-tailored bass and treble controls co-designed with Ian, utilizing a sophisticated blend of shelving, bandpass, and selectable LPF/HPF behaviors
• Transformer-balanced XLR output ensures expansive headroom, uncompressed dynamics, and commanding low-frequency extension
• High-headroom +24V internal power supply for clean dynamics and effortless low-end
• Active/passive pad and ground lift switches for enhanced compatibility to allow for more headroom if needed when using an active bass
• Flexible routing with 1/4-inch in/out and balanced XLR direct output for modern routing needs

At the heart of the circuit are 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 players to sculpt their 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.

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 users control over both the front end and final output of their tone.

Transformers

The Mantle features proprietary custom-wound “Sapphire” transformers. With more than a year of research, listening, and refinement, the Walrus engineering team has set a new benchmark with input and output transformers reflecting a 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

1/4-Inch TS Unbalanced Input (Hi-Z): Optimized for electric bass and buffered by a high-quality JFET stage to maintain impedance, detail, and instrument integrity.

1/4-Inch TS Unbalanced Output: Send your shaped signal to an amp or additional pedals.

Male XLR Balanced Output: Transformer-balanced for elevated DI tones that feel at home in high-end studio and live environments.

Power: 9VDC, 500mA center-negative. Internally boosted to +24V for massive headroom and clean, authoritative bass response.

Controls

Bass and Treble (Boost/Cut Filter System): The Mantle’s EQ is a sophisticated dual-behavior design. Both bass and treble controls feature eleven-position rotary switches with a true flat response at noon (position 6).

Boosting (positions 7–11): Begins as a shelf, gradually transitioning into a broad, musical bell as gain increases. Each increment adds +3dB, up to +15dB.

Cutting (positions 5–1): Introduces a steep -18dB/oct HPF or LPF at selectable points—30Hz to 120Hz (bass) and 8kHz to 1kHz (treble).

Gain Control

The gain control adjusts the amount of transformer-based gain applied to the signal. Ranging from -6dB to +23dB, this control draws directly from the input transformer, resulting in a tone that feels alive, dimensional, and expressive.

Switches

Active / Passive (-10dB Pad): Introduces a -10dB input pad for active basses or instruments with high-output preamps.

Ground Lift: Separates the XLR output ground from circuit ground to eliminate hum and ground-loop noise.

SPECIFICATIONS

• Power Requirements: 9VDC, 500mA, center-negative, 2.1mm
• Internal Boost Voltage: +24V
• Recommended Power Supply: Isolated
• Input Impedance: 1M ohm
• Output Impedance: 150 balanced, 150 unbalanced
• Noise Floor: Balanced -101dBV, Unbalanced -94dBV
• THD at 1kHz 1Vrms: 0.04%
• Frequency Response: 20Hz – 20kHz
• Gain Range: -6dB to +23dB
• EQ Boost Range: 0dB to +15dB
• Enclosure Size: 6.09 x 4.7 x 2.28 inches (154.78 x 119.35 x 57.98 mm)

We are Musictoner Musictoner

Since 1958, Chuck Levin’s Musictoner has been the trusted destination for musicians and audio professionals across Maryland, Virginia, and Washington, D.C. Family-owned and operated, our legendary music store delivers Everything in Music®—from instruments and recording gear to pro audio, rentals, and repair services.

Our team of musicians and industry experts lives and breathes gear, helping you build the perfect setup for your next performance, studio session, or installation. As an authorized dealer for top brands, we also offer our award-winning CHUCKSCLUSIVE line—exclusive, limited-edition instruments and collaborations recognized with the NAMM Top 100 Dealer Innovation Award for redefining what a music retail experience can be.

Chuck Levin’s isn’t just a store—it’s a community built by players, engineers, and creators who share a lifelong passion for sound. Stop by our legendary Wheaton, MD showroom or contact us anytime for expert advice, product questions, or the best possible deal on your next piece of gear.