dbx 676 - Class-A Vacuum Tube Preamp Channel Strip with High Voltage Gain and TRS/XLR Inputs/Outputs in Black Finish

The dbx 676 Class-A Vacuum Tube Preamp Channel Strip is an exceptional tool for adding warmth, clarity, and professional character to your recordings. Designed for both studio and live sound applications, the 676 combines a high-voltage tube preamp with a versatile channel strip processor. It offers a range of features including a 3-band semi-parametric EQ, a VCA compressor, and a PeakPlus limiter, all housed in a sleek black finish that complements any audio setup.

At the heart of the 676 is its Class-A, high-voltage (250V) vacuum tube preamp. This design ensures that the preamp delivers a rich, harmonically enhanced sound, adding a distinct analog warmth and sheen to your recordings. The preamp provides up to 55 dB of gain and includes a +48V phantom power option, a 20 dB pad, and a polarity invert switch, making it versatile for a wide array of microphones and direct instrument connections. The front-panel Hi-Z instrument input allows for easy connection of guitars and other instruments, while the pre-tube GAIN and POST TUBE ATTENUATION controls let you fine-tune the amount of tube drive for your desired sound. You can achieve a clean, open sound with a low pre-tube gain and high post-tube attenuation, or a rich, warm tone with higher pre-tube gain and lower post-tube attenuation.

The 676 features a 3-band semi-parametric EQ that provides precise control over your sound. The EQ section includes sweepable mid frequencies, with low and high shelving filters at 100 Hz and 10 kHz respectively. The mid frequency "Q" can be adjusted to narrow or wide settings, allowing for detailed tone shaping. An 80 Hz low cut filter is also available to eliminate subsonic noise and improve headroom by filtering out unwanted rumble and hum.

For dynamic control, the dbx 676 incorporates a VCA compressor modeled after the renowned dbx 162SL, known for its smooth, low-distortion compression characteristics. The compressor features selectable OverEasy (soft-knee) and hard-knee modes, with manual and AUTO attack and release settings. The attack and release times can be finely tuned for precise control over drum transients and vocal dynamics. The compressor also includes a sidechain jack for integrating external EQs or processors, enabling creative sidechaining applications. Additionally, the PeakPlus limiter ensures that your levels remain under control, preventing any unexpected clipping or distortion.

The 676's design includes a vintage-style LED backlit VU meter with selectable meter source, providing clear visual feedback for both preamp and compressor/limiter stages. It also offers parallel compression capabilities through its PREAMP and COMPRESSOR / LIMITER outputs, allowing for the recording of both processed and unprocessed signals simultaneously. The unit's robust build and high-quality components ensure reliable performance in both studio and live environments.

With its universal switch-mode power supply, the dbx 676 operates at 100-240 VAC, making it suitable for use worldwide. The unit's power requirements are 20 watts, and it includes a fuse for protection. Its physical dimensions are 19 x 8 x 3.5 inches, with a weight of 8.1 lbs and a shipping weight of 11 lbs.

In summary, the dbx 676 Class-A Vacuum Tube Preamp Channel Strip is a top-tier choice for those seeking to infuse their recordings with analog warmth and professional character. Its combination of a high-voltage tube preamp, versatile EQ, and advanced compression and limiting features make it an invaluable tool for achieving exceptional sound quality.

Features

• Class-A, high-voltage (250V) vacuum tube preamp for analog warmth and sheen
• Up to 55 dB of gain with +48V phantom power, 20 dB pad, and polarity invert switch
• Front-panel Hi-Z instrument input for direct instrument connections
• Pre-tube GAIN and POST TUBE ATTENUATION controls for flexible tube drive adjustment
• 3-band semi-parametric EQ with sweepable mid frequencies and 80 Hz low cut filter
• VCA compressor based on the dbx 162SL, with selectable OverEasy and hard-knee modes
• Manual and AUTO attack/release settings for dynamic control
• PeakPlus limiter for level control and preventing clipping
• Vintage-style LED backlit VU meter with selectable meter source
• PREAMP and COMPRESSOR / LIMITER outputs for parallel compression or unprocessed backup
• 1/4? preamp insert jack and compressor sidechain jack for additional processing options
• Electronically balanced XLR and TRS inputs/outputs for versatile connectivity
• Dimensions: 19 x 8 x 3.5 inches; Weight: 8.1 lbs; Shipping weight: 11 lbs
• Universal switch-mode power supply: 100-240 VAC, 50/60 Hz, 20 watts power requirement
• Operating temperature range: 32°F to 104°F

Specifications

Microphone Input

• Connector: Female XLR (Pin 2 Hot)
• Type: Transformer balanced/unbalanced, RF filtered
• Impedance: 1.9 kΩ
• CMRR: >85 dB from 20 Hz to 3 kHz, >70 dB from 3 kHz to 20 kHz

Instrument Input

• Connector: Tip-Sleeve 1/4-inch Jack
• Type: Unbalanced
• Impedance: 500 kΩ
• Maximum Input Level: +21 dBu unbalanced

Preamp Insert

• Connector: Tip-Ring-Sleeve 1/4-inch, RF filtered
• Type: Unbalanced, Tip = send, Ring = return
• Impedance: 50 Ω (send), 20 kΩ (return)

Line Outputs

• Connector: Male XLR and Tip-Ring-Sleeve 1/4-inch (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)

Compression Sidechain Insert

• Connector: Tip-Ring-Sleeve 1/4-inch, RF filtered
• Type: Unbalanced, Ring = output, Tip = input
• Impedance: 1 kΩ (output), 50 kΩ (input)

Vacuum Tube

• Type: 12AU7A / ECC82
• Grid Power Supply: +250V DC
• Heater Power Supply: +12V DC

System Performance

• Frequency Response:
  • Mic Input: 20 Hz to 50 kHz, +0/-1dB, 40 dB gain
  • Instrument Input: 30 Hz to 70 kHz, +0/-1dB, unity gain
• THD + Noise:
  • Mic In to Line Out: 0.25% typical at 0 dBu out, 1 kHz, 40 dB gain
  • Instrument In to Line Out: 0.2% typical at 0 dBu out, 1kHz, unity gain
• Equivalent Input Noise: 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
• Operating Temperature: 32F to 104F

Preamp Function Switches/Controls

• Instrument Input: Selects between microphone XLR input and front panel 1/4-inch 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

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
• 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
• Compression 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

Limiter

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

Power Supply

• Type: 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: 19 x 8 x 3.5 inches
• Weight: 8.1 lbs
• Shipping Weight: 11 lbs