Burl Audio B1D

The Burl Audio B1D is a high-octane 500 Series microphone preamplifier and DI module engineered for engineers seeking extra low-end weight, midrange density, and aggressive analog harmonic character. Built on the exact same direct-coupled, Class-A discrete circuit architecture as the standard B1, the B1D replaces the nickel output transformer with Burl Audio’s custom BX4 all-iron output transformer. The result is a punchier, darker, and more thunderous sonic footprint.

The B1D saturates in a rich, euphonic manner when driven hard. Using the stepped input gain and variable output level controls, engineers can dial in aggressive iron transformer colour while attenuating the final output level to avoid clipping converters.

Designed for versatile tracking sessions, the B1D features a transformer-coupled Impedance Select switch to optimise performance with low impedance microphones and condensers. A front-panel $1/4"$ Hi-Z instrument DI jack allows direct tracking of bass, electric guitars, and synthesisers, while a $-30\text{ dB}$ pad accommodates hot signals. 

Key Features

• Custom Burl Audio Iron Transformer: Pairs the BX3 input transformer with a proprietary all-iron BX4 output transformer for extra midrange drive, low-end punch, and rock character.

• Class-A Discrete Circuit Topology: Direct-coupled, zero-capacitor signal path delivers maximum transient speed and dynamic headroom.

• 70 dB Total Gain: High-gain capability to clean-boost low-output ribbon and dynamic microphones.

• Independent Gain & Level Staging: Stepped input gain knob paired with continuous output level trim for exact saturation shaping.

• Selectable Input Impedance: Low/High impedance switch for optimal load matching with ribbon mics.

• Front-Panel Hi-Z DI: $1/4"$ instrument input for direct tracking of bass, synth, and guitar.

• Essential Studio Controls: $-30\text{ dB}$ pad, $+48\text{V}$ phantom power, polarity reverse switch, and tri-color LED signal/peak indicator.

Technical Specifications

• Form Factor: Single-Slot 500 Series Module (VPR Alliance Compliant)

• Preamp Type: Solid-State Discrete Class-A Transistor

• Gain Range: Up to $70\text{ dB}$

• Input Transformer: Proprietary Burl Audio BX3

• Output Transformer: Proprietary Burl Audio BX4 (All-Iron Core)

• Circuit Path: Direct-Coupled, Zero-Capacitor Class-A Signal Path

• Inputs: Rear XLR (via 500 Series Rack Frame), Front $1/4"$ Hi-Z Instrument DI

• Outputs: Rear XLR (via 500 Series Rack Frame)

• Control Functions: Stepped Input Gain, Output Level Trim, Impedance Select Toggle, $-30\text{ dB}$ Pad, $+48\text{V}$Phantom Power, Phase Reverse (0∘/180∘)

• Metering: Tri-Color LED Signal / Peak Indicator