DBX 676 Tube Microphone/Instrument Preamp and Channel Strip

DBX 676 Tube Microphone/Instrument Preamp and Channel Strip Features

- Class-A Vacuum Tube Preamp with High Voltage Gain
- High-Visibility Vintage VU Meter
- Compressor designed from the dbx162SL
- 3-Band Semi-Parametric EQ
- ¼-inch (6.35mm) Jack and XLR Inputs and Outputs
- Front Panel Instrument Input
- Side Chain Insert

DBX 676 Tube Microphone/Instrument Preamp and Channel Strip Specifications

Mic Input:
- Mic Preamp Connector: Female XLR Pin 2 Hot; Electronically balanced/unbalanced
- Mic Preamp Input Impedance: 1.9 kΩ
- CMRR: >85 dB from 20 Hz to 3 kHz, >70 dB from 3 kHz to 20 kHz
- Frequency Response (Mic Input): 20 Hz to 50 kHz, +0/-1 dB, 40 dB gain
- THD + Noise (Mic In to LIne Out): 0.25% typical at 0 dBu out, 1 kHz, 40 dB gain

Instrument Input:
- Instrument Input Connector: Tip-Sleeve ¼-inch (6.35mm) Jack
- Input Type: (instrument) Unbalanced
- Instrument Input Impedance: 500 kΩ
- Max Input: (instrument) +21 dBu unbalanced
- Frequency Response (Instrument Input): 30 Hz to 70 kHz, +0/-1 dB, unity gain
- THD + Noise (Instrument In to Line Out): 0.2% typical at 0 dBu out, 1kHz, unity gain

Line Outputs (Preamp & Compressor/Limiter):
- Connector: Male XLR and Tip-Ring-Sleeve ¼-inch (6.35mm) (Pin 2 and Tip hot)
- Type: Servo-balanced/unbalanced
- Impedance: Balanced 30 Ω, unbalanced 15 Ω
- Maximum Output Level: > +21 dBm (into a 600 ohm load)

Vacuum Tube:
- Type: 12AU7A / ECC82
- Grid Power Supply: +250V DC
- Heater Power Supply: +12V DC
- Equivalent Noise Level: Typically > -123 dBu with a 150 Ω source load, 22 Hz to 22 kHz
- Noise Floor: Mic Insert to Comp Output: <-93 dBu, unity gain, EQ flat and no gain reduction

Preamp:
- Switches/Controls:
  - Instrument Input: Selects between microphone XLR input and front panel ¼" instrument input
  - +48V: Sends +48 VDC through 6.81 kΩ resistors to pins 2 and 3 of the microphone input
  - 20 dB Pad: Attenuates the microphone input by 20 dB
  - Polarity Invert: Reverses pins 2 and 3 of the microphone input XLR
  - 80 Hz Low Cut: Enables an 80 Hz, 12 dB/octave high pass filter in the microphone and instrument signal path
  - Gain Control Range: -∞ to +55 dB for Microphone Input; -∞ to +40 dB for Instrument Input
  - Post Tube Attenuation: -∞ to 0 dB
  - Peak Indicator: Illuminates RED when the Preamp is within 3 dB of clipping
- Insert Connector: Tip-Ring-Sleeve ¼-inch (6.35mm) Jack, RF filtered
- Insert Type: Unbalanced, Tip = send, Ring = return

Equalizer:
- Low Frequency: 100 Hz, Low-pass shelving filter
- High Frequency: 10 kHz, High-pass shelving filter
- Mid Frequency: Sweepable from 100 Hz to 8 kHz
- Function Switches/Controls: Narrow: Selects the "Q" of the MID Frequency EQ. "OUT" position Q = 0.9; "IN" position Q = 2.9
- Gain: (All Bands) Sweepable from -15 to +15 dB

Compressor:
- Threshold Range: -40 dBu to +20 dBu
- Threshold Characteristic: Selectable OverEasy or Hard Knee
- Ratio: Variable 1:1 to ∞:1; 60 dB maximum Compression
- Attack/Release Modes: Selectable Manual or Auto
- Manual Attack Time: Scalable program-dependent; Typically 400 dB/msec to 1 dB/msec
- Manual Release Time: Scalable program-dependent; Typically 4000 dB/sec to 10 dB/sec
- Auto Attack Time: Program-dependent, typically 15 ms for 10 dB, 5 ms for 20 dB, 3 ms for 30 dB
- Auto Release Time: Program-dependent, typically 120 dB/sec
- Output Level Control Range: -20 dB to +20 dB
- Peak Indicator: Illuminates RED when the Compressor/Limiter is within 3 dB of clipping
- Compressor Sidechain
  - Insert Connector: Tip-Ring-Sleeve ¼-inch (6.35mm) Jack, RF filtered
  - Insert Type: Unbalanced, Ring = output, Tip = input
  - Insert Impedance: 1 kΩ (output), 50 kΩ (input)

Limiter:
- Type: dbx PeakPlus
- Threshold Range: -4 dBu to + 22 dBu (off)
- Ratio: ∞:1
- Attack and Release: Program-dependent

Electrical:
- Power Supply: Universal switch-mode
- Operating Voltage: 100 - 240 VAC, 50/60 Hz
- Power Requirements: 20 Watts
- Fuse: T2.5AL 250V
- Turn-On Time: Approximately 2 seconds

Physical:
- Dimensions (W x H x D): 482.6 x 88.9 x 203.2 mm (19 x 3.5 x 8 inches)
- Weight: 5.0 kg (11.0 lbs)

Further Product Information Below

DBX 676 Data Sheet (PDF)

DBX 676 Quick Reference Guide (PDF)

DBX 676 Brochure (PDF)