Behringer 676 Tube Microphone Preamplifier FET Compressor Rack Processor

Behringer 676 is a tube microphone preamplifier and FET-style compressor designed for studio recording, mixing, and broadcast signal processing. It enables microphone, line, and instrument signal amplification with integrated dynamic control for recording engineers and production environments. This makes it ideal for studio signal chains where tube preamplification and compressor control are required.

The unit combines a vacuum tube preamplifier stage with a FET-style compressor in a single rackmount processor. Transformer-balanced inputs and outputs, tube amplification stages, and switchable equalization allow integration into recording and mixing workflows.

In practical operation, the preamplifier and compressor sections can function independently or together within a signal chain. Its control architecture supports microphone recording, instrument processing, and studio outboard compression applications.

Key Features

• Tube Microphone Preamplifier: Vacuum tube microphone and line preamp stage based on classic studio designs
• FET Style Compressor: Integrated compressor circuit modeled after classic FET compressor architecture
• Midas Transformers: Custom-built transformer-balanced input and output stages
• Selectable Input Sources: Microphone, line, and Hi-Z instrument input options
• Tube Circuit Design: Uses 12AX7/ECC83S and 12AT7/6072 vacuum tubes for signal amplification
• Two Band Shelving Equalizer: Integrated EQ section with selectable frequency filters
• Flexible Signal Routing: Preamplifier and compressor sections can operate independently or together
• Vintage Style Metering: Analog meter displays gain reduction or output level
• Rackmount Construction: Two rack unit chassis designed for studio racks and portable installations
• Universal Power Supply: Auto-ranging switch-mode power supply supports global mains voltages

Technical Specifications

Audio Inputs
Mic
Type: XLR, transformer balanced
Impedance: 500 Ω / 2 kΩ
Max input level: +14 dBu pad in, -1 dB pad out
CMRR: Typically > 90 dB @ 1 kHz, maximum gain
Frequency response: 20 Hz - 20 kHz ±1 dB
EIN noise at maximum gain: -122 dBu, 22 Hz - 22 kHz unweighted
Distortion (THD+N): <0.25% 50 Hz - 20 kHz, +4 dBu output
Maximum gain: +64 dB
Pad: Toggle switch, 0 dB / -15 dB
48 V: Toggle switch, applies +48 V phantom power to the mic input XLR

Line
Type: XLR, transformer balanced
Impedance: 15 kΩ
Max input level: +30 dBu
CMRR: Typically > 80 dB @ 1 kHz, unity gain
Frequency response: 20 Hz - 20 kHz ±1 dB
Noise at unity gain: -79 dBu, 22 Hz - 22 kHz unweighted
Distortion (THD+N): <0.25% 50 Hz - 20 kHz, +4 dBu output
Maximum gain: +20 dB

Hi-Z
Type: 6.35 mm (1/4") TS jack, unbalanced
Impedance: 47 kΩ / 2.2 MΩ
Max input level: +12 dBu
Frequency response: 20 Hz - 20 kHz ±1 dB
EIN noise at maximum gain: -105 dBu, 22 Hz - 22 kHz unweighted
Distortion (THD+N): <0.25% 50 Hz - 20 kHz, +4 dBu output
Maximum gain: +44 dB

Compressor
Type: XLR, transformer balanced
Impedance: 15 kΩ / 600 Ω
Max input level: +30 dBu
CMRR: Typically > 80 dB @ 1 kHz, unity gain
Frequency response: 20 Hz - 20 kHz ±1 dB
Noise at unity gain: -85 dBu, 22 Hz - 22 kHz unweighted
Distortion (THD+N): <0.25% 50 Hz - 20 kHz unity gain, +4 dBu output
Maximum gain: +40 dB

Audio Outputs
Preamplifier
Type: XLR, transformer balanced
Impedance: 90 Ω balanced
Max output level: +21 dBu
Phase reverse: Toggle switch, reverses the polarity of the output signal
Split/Join: Toggle switch, join connects the preamp output directly to the compressor input

Compressor
Type: XLR, transformer balanced
Impedance: 110 Ω balanced
Max output level: +26 dBu

Equaliser
Low frequency select: Toggle switch 70 Hz / 100 Hz / 200 Hz shelving
Low frequency cut/boost: Rotary switch -9 dB, -6 dB, -4.5 dB, -3 dB, -1.5 dB, 0 dB, +1.5 dB, +3 dB, +4.5 dB, +6 dB, +9 dB
High frequency select: Toggle switch 4.5 kHz / 7 kHz / 10 kHz shelving
High frequency cut/boost: Rotary switch -9 dB, -6 dB, -4.5 dB, -3 dB, -1.5 dB, 0 dB, +1.5 dB, +3 dB, +4.5 dB, +6 dB, +9 dB

Limiting Amplifier (Compressor)
Attack slow fast control: Range 800 µs to 20 µs
Release slow fast control: Range 1.1 s to 50 ms
Input level: Off to unity gain
Output level: Off to +40 dB gain
Ratio: Rotary switch BP – true bypass, 1:1, 4:1, 8:1, 12:1, 20:1, All > 100:1
Meter source select: Rotary switch, preamp output / gain reduction / compressor output
VU Meter: -20 dB to +3 dB (0 VU = +4 dBu)
Meter calibration trimmer: Set zero on the VU meter when in GR mode

Power Requirements
Mains voltage: 100 - 240 V~, 50/60 Hz
Power consumption: 28 W max
Mains connector: Standard IEC receptacle
Fuse: T 1.6 A H 250 V

Physical
Standard operating temperature range
5°C – 45°C (41°F – 113°F)

Dimensions (H x W x D)
88 x 160 x 483 mm
(3.47 x 6.30 x 19.0")

Weight
3.50 kg (7.71 lbs)