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dbx 676 Tube Microphone Preamp Channel Strip
The dbx 676 is a professional-grade channel strip designed for audio engineers seeking pristine sound quality and versatile control. Featuring a high-voltage, Class-A tube preamp section running on 250 volts, it delivers signals ranging from crystal clear to warm and colored tube tones. Incorporating the compressor/limiter design from the renowned dbx162SL and a 3-band parametric EQ with sweepable mids, the 676 offers comprehensive tonal shaping and dynamic control.
Built with a military-grade chassis, vintage-inspired controls, and high-visibility VU metering, the 676 is ideal for both studio recording and live sound applications. Its front-panel instrument input, side-chain insert, and separate preamp and compressor outputs provide professional flexibility for advanced routing and parallel processing.
Key Features
- Class-A Tube Preamp: High-voltage 250V Class-A vacuum tube preamp section for pristine or warm tonal coloration.
- Compressor/Limiter: Derived from dbx162SL with PeakPlus⢠limiting to prevent clipping and smooth dynamics control.
- 3-Band Parametric EQ: Sweepable mids (100 Hz to 8 kHz) with selectable Q (0.9 or 2.9), plus low (100 Hz) and high (10 kHz) shelving filters.
- Flexible Connectivity: Balanced XLR and ¼-inch inputs and outputs with a front-panel instrument input for direct instrument connection.
- Side-Chain Insert: ¼-inch jack for external signal processing, enabling advanced compression techniques like de-essing.
- Vintage-Inspired Controls: Classic knobs and switches paired with high-visibility VU metering for intuitive level and gain reduction monitoring.
- Robust Build: Military-grade chassis designed for reliability in studio and live performance environments.
Specifications
⢠General
ā Mic Preamp Connector: Female XLR, Pin 2 Hot, electronically balanced/unbalanced
ā Mic Preamp Input Impedance: 1.9 kĪ©
ā Common Mode Rejection Ratio (CMRR): >85 dB (20 Hz to 3 kHz), >70 dB (3 kHz to 20 kHz)
ā Instrument Input Connector: Tip-Sleeve ¼ā Jack (unbalanced)
ā Instrument Input Impedance: 500 kĪ©
ā Maximum Instrument Input: +21 dBu (unbalanced)
ā Preamp Insert Connector: Tip-Ring-Sleeve ¼ā, RF filtered (unbalanced)
ā Line Outputs (Preamp & Compressor/Limiter): Male XLR and Tip-Ring-Sleeve ¼ā (balanced/unbalanced)
ā Output Impedance: Balanced 30 Ī©, unbalanced 15 Ī©
ā Maximum Output Level: > +21 dBm (into 600 Ī© load)
ā Compressor Sidechain Insert Connector: Tip-Ring-Sleeve ¼ā, RF filtered
ā Vacuum Tube: 12AU7A / ECC82, +250 V DC grid power, +12 V DC heater power
⢠Frequency Response & Noise
ā Frequency Response (Mic Input): 20 Hz to 50 kHz, +0/-1 dB at 40 dB gain
ā Frequency Response (Instrument Input): 30 Hz to 70 kHz, +0/-1 dB at unity gain
ā THD + Noise (Mic In to Line Out): 0.25% typical at 0 dBu out, 1 kHz, 40 dB gain
ā THD + Noise (Instrument In to Line Out): 0.2% typical at 0 dBu out, 1 kHz, unity gain
ā Equivalent Noise Level: Typically > -123 dBu with 150 Ī© source load, 22 Hz to 22 kHz
ā Noise Floor: Mic Insert to Compressor Output: < -93 dBu, unity gain, EQ flat, no gain reduction
⢠Compressor / Limiter
ā Compressor Threshold Range: -40 dBu to +20 dBu
ā Threshold Characteristic: Selectable OverEasy⢠or Hard Knee
ā Compressor Ratio: Variable from 1:1 to infinity:1, with max 60 dB compression
ā Attack/Release Modes: Selectable manual or auto
ā Manual Attack Time: Scalable, typically 400 dB/msec to 1 dB/msec
ā Manual Release Time: Scalable, typically 4000 dB/sec to 10 dB/sec
ā Auto Attack Time: Program-dependent, typically 15 ms for 10 dB compression, faster with higher compression
ā Auto Release Time: Program-dependent, typically 120 dB/sec
ā Output Level Control Range: -20 dB to +20 dB
ā Peak Indicator: LED illuminates red within 3 dB of clipping
ā Limiter Type: dbx PeakPlus⢠program-dependent attack/release
ā Limiter Threshold Range: -4 dBu to +22 dBu (off)
ā Limiter Ratio: Infinity:1
⢠EQ
ā Low Frequency: 100 Hz shelving filter
ā Mid Frequency: Sweepable 100 Hz to 8 kHz with selectable Q (0.9 or 2.9)
ā High Frequency: 10 kHz shelving filter
ā Gain Range: ±15 dB on all bands
⢠Controls and Features
ā Front Panel Instrument Input: Select between microphone XLR input and front ¼ā instrument input
ā Phantom Power: +48V switch through 6.81 kĪ© resistors
ā Pad: 20 dB pad attenuates microphone input
ā Polarity Invert: Reverses pins 2 and 3 of the microphone input XLR
ā Low Cut Filter: 80 Hz high-pass filter at 12 dB/octave slope
ā Gain Control Range: Microphone Input: -ā to +55 dB; Instrument Input: -ā to +40 dB
ā Peak Indicators: LED warning for preamp and compressor clipping within 3 dB
⢠General Information
ā Operating Voltage: 100 ā 240 VAC, 50/60 Hz
ā Power Consumption: 20 Watts
ā Dimensions: 3.5āH x 19āW x 8āD (88.9 mm x 482.6 mm x 203.2 mm)
ā Weight: 8.1 lbs (3.7 kg)
Package Content
- dbx 676 Tube Microphone Preamp Channel Strip unit
- Power cable
- User manual


