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dbx 540 - Tube Mic Preamp - Used  From dbx

500 Series Tube Mic Preamp from dbx


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dbx Professional

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Condition: Used, Excellent

Manufacturer's Description from dbx

The dbx 540 features a Class A tube preamplifier, switchable phantom power, phase invert, selectable -20dB pad, and a super fast in-line optical compressor. The front panel includes a TRS microphone input - a standout feature typically not found on 500-series preamps.

The easy-access interchangeable 12AX7 preamp tube allows you to experiment with a variety modern and vintage tubes to customize the 540’s sound and performance to your taste. The switchable (in/out) compressor provides adjustable attack and release, and when it’s in use, the on-board VU meter automatically changes from displaying master level to amount of gain reduction, so you can view the exact results of the compression being applied. Editing is done using our smooth, responsive hand-machined controls. And last but not least: The dbx 540’s audio circuit uses LME49720 ultra-low distortion/low noise Op Amps, for superb audio output.



Suitable for use in all 500-series-compatible systems

12AX7 electron tube

Class A transformerless high voltage signal path

Adjustable optical compressor

Switchable phantom power

Switchable phase invert

Switchable -20dB pad

Dual-function VU meter: master volume / gain reduction

Input gain control

Output volume control

dbx Professional


Mic/Line Input Connectors: TRS balanced

Impedance: 3k Ohms

Mic Input Gain: 10dB to 60dB

Phase Reversal: Switchable

Phantom Power: +48V, switchable

Instrument Input Connector: 1/4” jack unbalanced (or XLR from back panel)

Instrument Input Gain: 0dB to 45dB

Output Connectors: XLR & 1/4" jack (back panel)

Line in Frequency Response: 10Hz to 40kHz within 1dB

Mic in Frequency Response: 10Hz to 40kHz within 2.5dB

Compressor Ratio: 1:1 - 10:1

Compressor Attack: 1ms - 100ms

Compressor Release: 0.1s - 3s

Shelving filter: 80Hz

Slope: 16dB

VU meter: -20dBu - +3dBu

THD: 0.05% (unweighted)

Signal to Noise: >101dB

Power Supply: 500 Series power supply required