The Walrus Audio Mantle Bass Preamp & DI is a premium analogue preamp and direct box developed in close collaboration with bassist Ian Martin Allison. Designed for stage, studio and home use, Mantle provides a refined foundation for electric bass with extensive headroom, musical gain, flexible EQ and transformer-balanced output.
At the heart of Mantle are Walrus Audio’s proprietary Sapphire Transformers. The input transformer draws from classic Neve-style architecture for authoritative low end and midrange presence, while the output transformer is based on the output stage of an API 312, providing balanced output alongside rich harmonic character.
A high-impedance JFET input buffer preserves detail and playing dynamics before the signal reaches the transformer gain stage. Gain is adjustable from -6dB to +23dB, providing everything from attenuation to clean, harmonically rich amplification.
The Bass and Treble controls use 11-position rotary switches with a flat setting at position six. Boost settings provide up to +15dB in 3dB increments, while the cut positions introduce selectable high-pass and low-pass filtering for precise control over the frequency extremes.
Mantle operates internally at +24V for increased headroom and clean low-frequency response. A -10dB Active/Passive pad accommodates higher-output instruments, while Ground Lift helps address ground-loop noise when using the balanced XLR output.
With unbalanced 1/4" input and output plus a transformer-balanced XLR DI output, Mantle provides a flexible central preamp for sending a polished bass signal to an amplifier, interface, mixer or additional effects.
Key Features
Developed with bassist Ian Martin Allison
Premium analogue bass preamp and DI
Proprietary custom-wound Sapphire input and output transformers
High-impedance JFET input buffer
Transformer-based gain from -6dB to +23dB
11-position Bass and Treble controls
Up to +15dB of musical EQ boost
Selectable high-pass and low-pass filtering
Transformer-balanced XLR DI output
Internally boosted to +24V for increased headroom
-10dB pad for active and high-output basses
Ground Lift for live and studio setups
Flexible 1/4" and balanced XLR routing
Controls
Gain: -6dB to +23dB of transformer-based gain
Bass: 11-position boost/cut and high-pass filter control
Treble: 11-position boost/cut and low-pass filter control
Active / Passive: Engages a -10dB input pad when required
Ground Lift: Separates XLR output ground from circuit ground
