Gain Reduction | Pro Audio Hardware Compressors and Limiters

The ProVLA II is a tube driven Vactrol®-based Compressor / Leveling amplifier designed to excel in any professional audio environment. Superior performance and an incredible tone makes the ProVLA II and indispensable tool for tracking, mixing, mastering, dynamic control of live sound sources or for use in broadcast audio.
 
Capable of delivering a far more musical natural sounding and sonically transparent compression than competitive units in its class, the ProVLA II uses an Opto-electronic circuit rather than the more typical design VCA driven level detection circuit. This VCA-less design coupled with a 12AT7 vacuum tube in the gain stage makes the Pro-VLA II the ideal dynamic control device for critical audio applications.
 
Exceptional signal integrity with extremely low noise and low distortion is achieved in the ProVLA II by utilizing a transformerless design throughout.
 
Vactrol® Technology
Unlike typical compression units that use Voltage Controlled Amplifiers (VCA’s) to handle level detection, the Pro VLA II’s Opto-electronic design allows a far more transparent and musical sounding compression without sounding aggressive or un-natural. This Vactrol based optical electronic circuitry is the basic component of the classic highly sought after compressors of past.
 
Vactrol® design allows the ProVLA II to react to audio signal in much the same way the eye naturally adjusts to fluctuations in light levels – smoothly, quietly and almost imperceptibly.
 
Soft Knee Leveling
The ProVLA II is a soft knee leveling amplifier by design. Although capable of providing dramatic compression effects, the ProVLA II was designed to excel in any application where transparent, expressively musical dynamics control is desired.
 
Comprehensive Metering
Large highly visible backlit analog VU meters accurately display input and output levels while extremely fast 10-segment LED’s display gain reduction. For added functionality, the LED’s display either average level for mastering & mixing applications or peak hold for monitoring individual sources when tracking audio.
 
Versatile I/O
XLR and 1/4-inch TRS balanced inputs and outputs are provided to ensure the ProVLA II can connect with any audio source or hardware. A +4dBu/-10dBu mode switch optimizes ProVLA II I/O for either consumer or professional equipment.
Features
 
  * VCA-Less Vactrol Opto-Compression Design
  * Mastering Quality Audio Signal Path with Tube Gain Stage
  * Enhanced Link Mode – While in stereo link mode, channel 1 level control acts as a master output level and channel 2 becomes a balance control between them, - optimizing the Pro-VLA II for use as a mastering tool
  * Variable Threshold, Ratio & Output Controls
  * LED Backlit VU Input/Output Level Metering
  * LED Metering Indicates Both Average Level And Peak Hold
  * Accurate Ten Segment LED Gain Reduction Metering
  * +4dBu/-10dBu Mode Switch Optimizes Pro-VLA II For Interface with Professional OR
  * Consumer Grade Components
  * Active Balanced XLR And ¼-Inch Inputs & Outputs
  * Toroidal Transformer Reduces Mechanical & Electrical Hum
 
Specifications
Attack Time 0.25msec. to 50msec. variable
Dimensions 3.5in x 19in x 9.2in / 8.9cm x 48.3cm x 23.3cm
Dynamic Range greater than 100dB (20-20KHz)
Equivalent Input Noise @+4dBu: -99dBu (''A'' weighted) / @-10 dBV: -107dBu (''A'' weighted)
Frequency Response 10Hz to 100KHz (+/- 0.5dB)
Input Impedance 10K Ohms
Maximum Attenuation 30dB
Maximum Input Level +20dBu (in +4dBu mode) / +10dBV (in –10dBV mode)
Maximum Output Level +20dB max
Release Time Variable 150ms to 3s
Slope Variable 2:1 to 20:1
Total Harmonic Distortion less than 0.1% (typical)
Weight 10.5lbs / 4.76kgs
 
ART Tube Compressors deliver analog leveling/compression designed to work seamlessly with any recording, sound-reinforcement, and electronic instrument application. Our Tube Compressors excel at making tracks sound rich and full for both live audio engineering and studio recording applications.
 
ART’s tube compression circuitry is a hybrid design utilizing the latest and most advanced analog and tube technology, and has exceptional signal integrity with extremely low noise.
 
ART tube compressors utilize optical electronics (a device known as a Vactrol®), coupled with a 12AT7 vacuum tube gain stage for superior musical performance. Unlike typical compressors which use VCAs to control level detection, ART tube compressors are very musical, expressive and natural sounding.
 
Retail:
 
£200-£300
 
Used:
 
Verdict:
 
A very characteristic compressor, perfect on a budget. Some people use it on the mix bus, but otherwise ideal for compressing drums and bass with character. The only problem with this unit is the lack of side-chain. A good project for diy-ers. Good built and professional look and feel.

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Valve compression is now universally recognised as one of the essential tools for today’s recording engineer. The Ivory 5021 provides everything you would expect from a TL Audio compressor - first class audio quality, bags of flexibility and a price tag so modest you'd be forgiven for thinking it was a printing error! Now the new 5021 features hard and soft knee modes, four attack and release times, an improved optical gate design and an optional digital output. Like the C-1 compressor, the 5021 uses our own special transconductance amplifier design that avoids the use of VCAs - ensuring maximum audio transparency. So whether you’re hitting the end stops or just providing gentle dynamic control, the 5021 delivers super-smooth results every time!
 
The 5021 employs two valve stages per channel, in the form of a Sovtek ECC83/12AX7A twin triode valve run from a stabilised 150V DC supply. One stage is in the preamp, and the other is in the gain control element of the compressor.
 
  * Each channel provides continuously variable control of: Input Gain, Threshold, Ratio, Gain Make-Up and Output Gain
  * NEW Four attack times: from 'Fast' (0.5mS) to 'Slow' (40mS)
  * NEW Four release times: from 'Fast' (40mS) to 'Slow' (4S)
  * NEW Hard/soft knee compression modes
  * Automatic "Hold" facility reduces LF distortion
  * NEW Optical gate with variable control of threshold (from -10dB to 'off')
  * ‘Bypass?and 'Stereo link' modes
  * Switchable VU meters provide indication of output level or gain reduction
  * Drive and Peak LEDs to indicate internal signal levels
  * Front panel instrument inputs
  * Balanced XLR line inputs/outputs duplicated on unbalanced jack connectors
  * Sidechain insert points
  * NEW Optional 24 bit stereo digital output)
 
Specifications:
 
  * Balanced Line Input: Maximum level: +26dBu
  * Balanced Line Outputs: Maximum level: +26dBu
  * Frequency Response: 10Hz to 40kHz, +0, -1dB
  * Noise: -80dBu (22Hz to 22kHz)
  * Dynamic Range: 106dB (Line input @ 0dB gain)
  * Power Supply: Consumption: 20VA typical
  * Dimensions: 483 x 200 x 88mm
  * Shipping Weight: 6kg
 
Retail:
 
£490
 
$499-999
 
Used
 
£200-£300
 
$280-420
 
Verdict,
 
Not recommended on the mix bus. FMR RNC is a better choice at this price point. Opinion about this product is reflected in the vast numbers that are listed on ebay & other used audio sites every week. Some users complain about that valves not affecting the sound much. There are better alternatives. If you are after a transparent compressor, the FMR RNC will do a better job. If you are looking for a compressor for colouring your sounds, look for the Symetrix 501 (toggle switch) or the Ashly SC-50.

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The Behringer T1952 TUBE COMPOSER Interactive Tube Dynamic Processor. Affordable, professional signal processor with tube technology.
 
The Behringer T1952 TUBE COMPOSER offers various dynamic processing functions: fully automatic as well as manual compression, expander/gate, and program limiting. It combines the advantages of hard-knee and soft-knee compression in a single processing function. The result is entirely natural and transparent, even in the case of extreme compression ratios. It also incorporates a warmth control, automatic or manually controllable attack and release times, switchable high-pass filter and monitor function for side chain, a peak-limiting circuit that combines clipper and program limiter, expander/gate circuit for gentle disturbance suppression, and displays for input and output levels and gain reduction. The T1952 also features a switchable stereo link mode and can be set to +4 dBu or -10 dBV. Servo-balanced inputs and outputs with XLR and 1/4 inch TRS connectors and a relay-controlled hard bypass function ensure trouble-free operation and prevent nasty surprises in the case of power failures.
 
The main features of the Behringer T1952 TUBE COMPOSER include:
 
  * Special Warmth control and selected 12AX7 tubes allow you to precisely add the desired amount of tube sound to your audio
  * IKA (Interactive Knee Adaptation) combines soft knee and hard knee characteristics
  * Automatic or manually controllable attack and release times
  * Switchable high-pass filter and monitor function for side chain
  * Compression switchable between interactive knee and hard knee operation
  * IGC (Interactive Gain Control) peak limiting circuit combines clipper and program limiter
  * IRC (Interactive Ratio Control) expander/gate circuit for gentle disturbance suppression
  * Precise displays for input and output level and gain reduction
  * Stereo link function
  * Servo-balanced inputs and outputs with 1/4 inch TRS and gold-plated XLR connectors
  * Relay-controlled hard bypass switch with auto bypass function in case of power failures (safety relay)
 
Retail
 
$150
£107-129
 
Used
 
$50-100
£35-£70
 
depending on condition. missing lamps / meters / knobs / rack rash bring the price down.
 
Verdict:
 
Discontinued, mass produced, but excellent value compressor and ideal for beginners learning compression. Replace the standard Sovtek valves with different 12AX7 tubes (easily done) to experiment and get new characteristic sounds. Amps can also be replaced but can a be a little more tricky.

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The OC8E is a 2U standard 19" rack-mount multi-channel optical compressor.
 
Built on the success of the original OC8, the OC8E adds 8 VU meters and more detailed compression controls to an already superb optical compressor.
 
Tailored to suit a wide variety of applications, the OC8E is perfectly suited for use as a multi-channel compressor for a wide variety of audio applications. Optical compressors are sought after for the distinctive musicality they give to vocals, guitars and other instruments. The OC8E 's adjustable compression ratio, attack, release and output controls allow you to generate a distinctive soft, rich character while providing magnificent control over dynamics.
 
Fantastic for use as inserts on your multi-channel recording tracks the OC8E is a great addition to any home or pro studio looking to take advantage of the benefits that optical compression can provide.
 
  * 8 x fast electro-optical compressor
  * Bypass/on switch
  * 8 x individual compression ratio controls
  * Tri-state LED indicator
  * 8 x individual attack & release controls
  * 110v-220v Internal power supply
  * 8 x individual output level controls
  * Size: 2U Rack
  * 8 x individual output VU level indicators
  * Low noise, wide bandwidth and superior transient response
  * Class A transformerless high voltage signal path
  * ADAT Option PR8IIA
  * Low noise, wide bandwidth and superior transient response
  * Housing: Metal
 
Retail
 
$419
£298.71
 
Used
 
± £194
± $274
 
Verdict:
 
A useful tool for live work but not necessarily the best sound quality for studio work. Not very popular on eBay. For this price, an Art Pro VLA II is a better choice. Alternatively a pair of Ashly SC-50, which have recently gone up in price and continue to go up.

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