The Sanctuary Perspective

The Radial J48 is the world's most trusted active direct box, engineered to handle high-output active acoustic pickups, active electric basses, and electronic keyboards without distortion. While standard phantom-powered DI boxes often clip when driven by high-output instruments, the J48 utilizes a proprietary internal switching power supply to step up 48V phantom power to higher internal rail voltages. This expanded dynamic headroom guarantees a ruler-flat frequency response from 20Hz to 20kHz, zero harmonic square-wave distortion, and unmatched signal transparency on stage or in the studio.

Product Intelligence & Signal Integrity Profile

• Best For: Active Electric Basses, High-Output Acoustic Pickups, Digital Modelers, Keyboards, Recording Studios, and Major Touring Stages.
• Sound Character: Completely transparent, punchy, and uncolored with deep low-end extensions, extended high-frequency clarity, and pristine transient handling.
• Compared To: Offers significantly higher signal headroom than standard active DI boxes, preventing active bass preamps from overloading the input stage while maintaining cleaner power rail distribution via 48V phantom power.
• Sanctuary Expert Note: "The J48 is the undisputed industry standard for active bass and piezo acoustic instruments. If you plug a high-output instrument into a standard DI and hear subtle clipping or harshness on low notes, the J48 solves it instantly with its stepped-up internal rail headroom."

Key Features & Stage Engineering Highlights

• Stepped-Up Internal Power Supply: Converts standard 48V phantom power into higher internal operating voltages, delivering exceptional dynamic headroom to handle hot instrument signals without rail clipping.
• Unique Stereo-to-Mono Merge Function: Converts the Thru jack into a secondary input, allowing stereo keyboards, DJ controllers, or tablet feeds to be summed passively into a single mono XLR output.
• Polarity Reverse Switch: 180° phase flip reverses the XLR pin orientation to correct out-of-phase stage monitors or resolve acoustic feedback problems instantly.
• Selectable Pad & High-Pass Filter: Features a -15dB input pad for ultra-hot line-level feeds and an 80Hz low-cut filter to eliminate muddy stage rumble and low-end resonance.
• Isolated Ground Lift Architecture: Employs a capacitive ground-decoupling network that maintains phantom power draw while completely eliminating 60-cycle ground loops and hum.
• Book-End Steel Construction: Built housed inside Radial's legendary 14-gauge steel I-beam chassis to protect internal switches and connectors from harsh touring environments.

Technical Specifications

• Audio Circuit Type: Proprietary Active Analog Circuit with Low-Noise Operational Amplifiers
• Number of Channels: 1 (Mono)
• Frequency Response: 20Hz – 20kHz (± 0.5dB)
• Dynamic Range: 109dB
• Total Harmonic Distortion (THD): 0.005% @ 1kHz
• Maximum Input Level: +10dBu (+25dBu with -15dB Pad engaged)
• Input Impedance: 220kΩ Unbalanced
• Output Impedance: 600Ω Balanced XLR
• Switches: -15dB Pad, 80Hz Low-Cut Filter, 180° Polarity Reverse, Ground Lift, Merge Switch
• Connections: 1 x 1/4" Input, 1 x 1/4" Thru (or Input 2 in Merge Mode), 1 x Balanced XLR Output
• Power Requirement: 48V Phantom Power (No Batteries Required)
• Chassis: 14-Gauge Heavy Duty Steel

Audio circuit type: Proprietary analog circuit with low-noise op-amp
Frequency response: 20Hz ~ 20kHz
Dynamic range: 109dB
Total harmonic distortion: 0.002% @ -5dBu
Intermodulation Distortion: 0.003% @ -3dBu
Phase Deviation: +10º at 20Hz | 0º at 1kHz | -1º at 20kHz
Input Impedance: 220kΩ - ¼" input
Output Impedance: 200Ω - XLR output
Equivalent Input Noise: -103dBu
Noise Floor: -99dB below 0dBu
Maximum Input: +10dBu

Features

Input pad, Mono Sum, 180° polarity reverse, Ground lift, HPF
Input Connectors: 1/4"
Output Connectors: Balanced XLR, 1/4" Thru

General

Construction: 14 gauge steel chassis and outer shell
Size (L x W x D): 3.3" x 5.0" x 2" (84 x 127 x 48mm)
Weight: 1.55 lb (720 g)
Power: 48V phantom - proprietary digital switching
Conditions: For use in dry locations only between 5°C and 40°C
Warranty: Radial 3-year, transferable