The VOXBOX Combo Tube Channel Strip from Manley Labs is a signal processor with mic preamp, compressor, EQ, and De-Esser/Limiter. While the unit can be used as a single input channel strip, it can also process 2 independent audio signals; one through the mic preamp/compressor and the other through EQ/De-Esser/Limiter. The original design idea was intended for vocal processing. However, the VOXBOX also excels at processing drums, guitar, bass, and stereo mixes.

The VOXBOX incorporates many of Manley's technological innovations including the preamp from the Mono Mic Preamp, an electro-optical ELOP compressor, a Pultec-style mid-EQ, and a dedicated ELOP de-esser/limiter. The mic preamp features a hand-wound iron transformer with nickel laminations, negative feedback gain circuit, and triode vacuum tube circuit. The ELOP compressor is an electro-optical limiter with a fixed ratio of 3:1. The attack, release and threshold knobs adjust 4 different time constraints simultaneously resulting in "parametric compression," which allows for a broad spectrum of professional results for any vocal, instrument, or mix bus signal. While other manufacturer's designs have the compressor post mic pre, the VOXBOX places the circuit before the mic preamp making it near impossible to clip. This also shortens the signal path and ensures a quality, low noise signal.

The EQ section features Manley's Pultec-style Mid EQ, a 3-band EQ (low peak, mid dip, high peak) with an extended frequency range covering 20 Hz to 20 kHz. The de-esser/limiter features another ELOP circuit with 4 notch frequencies to tame sibilance and a 5th setting to provide a LA-2A style limiter. This design allows for compression of the signal pre-EQ and limiting post-EQ. Another useful feature is the silent bypass switches, which allow for the engaging and disengaging of any circuit during recording or playback without any audible artifacts. The large VU meters offer a 5-way toggle switch for monitoring the line input, preamp output, final output, compression gain reduction, and de-esser/limiter action. Handmade in the USA, the unit is housed in a 3U steel chassis with a CNC machined 1/4" faceplate that is also inlaid with laser engraved inserts. The VOXBOX ships with a standard IEC power cable.

Mic Preamp
  • Phantom 48 Volts: 48v power for microphones requiring phantom power
  • 3-way Toggle Switch for High Pass Filter: Flat (bypassed), 80, and 120 Hz
  • 3-way Toggle Switch for Phase Reverse and Line Selection: 0, line, and 180
  • 1/4" 100 KΩ direct injection (DI) input for instruments
  • Mic Preamp Gain Switch: 40 to 60 dB of negative feedback gain
  • Input Level: Input attenuator or variable pad for mic, line, and DI
  • Manley ELOP circuit
  • Fixed 3:1 ratio
  • Continuously variable threshold control
  • 5-way Selection Knobs for Attack and Release: Fast, med fast, medium, med slow, and slow
  • Compress 3:1 Bypass: Silent bypass allows for discretely engaging the compressor during playback or recording
  • Link: Selects stereo operation of a second VOXBOX
  • Pultec style mid-EQ with extended frequency range
  • Low Peak Frequency: 11 position knob - 20 to 1000 Hz
  • Low Peak Boost: 0 to +10 dB
  • Mid Dip Frequency: 11 position knob - 200 to 7000 Hz
  • Mid Dip: 0 to -10 dB
  • High Peak Frequency: 11 position knob - 1.5 to 20 kHz
  • High Peak Boost: 0 to +10 dB
  • EQ In Bypass: Silent bypass switch allows for discretely engaging the EQ during playback and recording
  • EQ Input: 3-way toggle switch for selecting line input, preamp output, and insert return
De-Esser & Limiter
  • De-Ess Bypass: Silent switch for discretely engaging the de-esser during playback and recording
  • De-Ess Select: 5 position rotary switch for selecting de-essing frequencies
  • Limit: Setting removes frequency selection and works as an electro-optical limiter
  • Continuously variable threshold control
VU Meter
  • Full size illuminated Sifam VU Meter
  • 5-Way Switch: Line input, preamp output, EQ output, compressor gain reduction, and de-esser/limiter action
Additional Features
  • Auto-Mute Warm Up Delay: 30 seconds
  • Hand-wound Manley iron input transformer
  • Silent conductive plastic input attenuator
  • Magnetic field containment
  • Smart-grounding

Input / Output 1 x Mic Input: Balanced transformer coupled XLR at 2 kΩ 
1 x Line Input: Balanced transformer coupled XLR at 3 kΩ
1 x Line Input: Balanced transformer coupled 1/4" TRS at 3 kΩ
1 x Insert Input (EQ Section): Balanced transformer coupled XLR at 3 kΩ
1 x Insert Input (EQ Section): Balanced transformer coupled 1/4" TRS at 3 kΩ
1 x Direct Input: Unbalanced 1/4" at 100 kΩ
1 x Preamp Output: Balanced transformer coupled XLR at 50 Ω
1 x EQ Output: Balanced transformer coupled XLR at 50 Ω
1 x Preamp Output: Unbalanced transformer-less 1/4" TRS (+4 dB)
1 x EQ Output: Unbalanced transformer-less 1/4" TRS (+4 dB)
1 x De-Esser stereo link via RCA jack
1 x Compressor stereo link via RCA jack
Compressor Ratio: 3:1
Maximum Gain Reduction: 16 dB
Attack Time: 4 to 70 ms
Release Time: .3, .5, 1, 2, 5 Sec
EQ Section Low Peak: 20, 35, 50, 70, 100, 150, 200, 300, 500, 700, 1000 Hz +10 dB
Mid Dip: 200, 300, 500, 700, 1k, 1.5k, 2k, 3k, 4k, 5k, 7k Hz -10 dB
High Peak: 1k, 2k, 3k, 4k, 5k, 6.4k, 8k, 10k, 12k, 16k, 20k Hz +10 dB
De-Esser & Limiter Ratio: 10:1
Maximum Gain Reduction: 32 dB
Attack Time: 2 ms
Release Time: 500 ms
De-Ess Notch Frequencies: 3, 6,9,12 kHz, none (Limit)
Tubes Mic Preamp: 1 x 12AX7LPS and 1 x 6414
EQ Section: 1 x 5751 and 1 x 6414
Headroom Headroom (Referenced to +4 dBv): 27 dB
Frequency Response (Audio) Preamp: 20 Hz to 60 kHz ±1 dB
EQ: 10 Hz to 100 kHz ±1 dB
THD & Noise Mic Preamp THD & Noise (1kHz @ +20 dBm): 0.3% 
EQ THD & Noise (1kHz @ +20 dBm): 0.3%
Both THD & Noise (1kHz @ +20 dBm): 0.35%
Noise Floor Mic Preamp Noise Floor (Settings to Minimum): -86 dB
EQ Noise Floor (Settings to Minimum): -89 dB
Both (Settings to Minimum): -84 dB
Signal to Noise Ratio Mic Preamp: 113 dB typical
EQ: 116 dB typical
Both: 110 dB typical
Maximum Input Level Mic: +20 dB
Line: +40 dB
Maximum Output Maximum Output (1.5% THD): +31 dBv
Gain Microphone Input: 60 dB
Line Input: 20 dB
Insert Input: 20 dB
Power Power Supply: 200 mA @ 115 VAC
Power Consumption: 24 W
Mains Voltage Frequency: 60 Hz
Fuse: Mains 120 VAC = 1 A Slo-Blo
Rackmountable 3U
Dimensions (W x H x D) 19.0 x 5.3 x 10.0" / 48.3 x 13.3 x 25.4 cm
Weight 14.0 lb / 6.4 kg

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