Grace Design m303 is a single-channel, active DI box with full galvanic isolation, a Lundahl transformer and 48 V phantom power, in a rugged extruded aluminium chassis. Grace Design's first dedicated DI box brings the transparency of the m-series preamp signal path to the stage and studio, offering exceptional dynamic headroom and sonic clarity in a compact format accessible to any audio engineer.
Galvanic isolation and a Lundahl transformer
Active DI boxes without galvanic isolation are susceptible to ground loops and mains interference on a busy stage. The m303 eliminates this at source through full galvanic isolation: no DC current flows between input and output, blocking ground loops before they reach the FOH mixer. A custom, hand-wound Lundahl nickel-core transformer with magnetic shielding delivers the low-end clarity and high-frequency detail that Hugh Robjohns of Sound On Sound described as the best-sounding DI box he had ever heard. The 1 MΩ input impedance is ideal for passive guitar and bass pickups, and a maximum input level of +27 dBu handles even the hottest line-level signals without distortion.
Simple operation on stage and in the studio
A FOH engineer needs reliability and predictability in demanding stage conditions. The m303 delivers exactly that: a -13 dB pad for loud sources, a ground lift switch to prevent hum, a 1/4" thru output to an amp or monitor, and a power LED confirming phantom presence. The quarter-inch extruded aluminium chassis withstands stage conditions, and recessed connectors protect against accidental cable pulls. At just 4 mA of phantom current draw the m303 does not stress mixer channels or interfaces. Available in mono (m303), stereo (m303s) and 8-channel rackmount (m308) versions.
KEY FEATURES
- Active single-channel DI box with full galvanic isolation
- Custom Lundahl transformer with nickel core and magnetic shielding
- 48 V phantom power, only 4 mA current draw
- 1 MΩ input impedance, ideal for passive pickups
- Maximum input level +27 dBu with large dynamic headroom
- -13 dB pad for loud sources
- Ground lift (ISO) switch
- 1/4" thru output to amp or monitor
- Recessed connectors, power LED, 1/4" aluminium chassis
- Also available in stereo (m303s) and 8-channel rackmount (m308) versions
TECHNICAL SPECIFICATIONS
- Manufacturer: Grace Design
- Type: active single-channel DI box with galvanic isolation
- Input impedance: 1 MΩ
- Maximum input level: +27 dBu
- Pad: -13 dB
- Output transformer: custom Lundahl, nickel core, magnetic shielding
- Power: 48 V phantom, 4 mA draw
- Input: 1/4" unbalanced jack
- DI output: XLR balanced
- Thru output: 1/4" jack
- Switches: -13 dB pad, ground lift / ISO
- Indicator: power LED (green)
- Chassis: 1/4" extruded aluminium, anodized, cobalt blue
- Dimensions: 81 x 44 x 134 mm (W x H x D)
- Weight: under 0.5 kg
- Manufacturer warranty: 20-year EON
