Gain Reduction | Pro Audio Hardware Compressors and Limiters

C300 is an easy to use dual engine dynamics processor that gives you superior compression/limiting and gate/expansion feasibilities. It features flexible control of the signal path, 16 gate/expander and 16 compressor/limiter audio-optimized presets with intelligent TC multi-band and full-band technology, innovative new style compression, state-of-the-art TC quality, and an extremely intuitive and straightforward user interface that gives you access to complex and comprehensive dynamic processing with a few buttons and simple operations only.
 
C300 is mainly meant to be used in insert applications.
 
The C300 gives you source-based presets that are tailor-made for various types of sources. Depending on the preset you select you have access to intelligent TC full-band- or multi-band technology.
The C300 multi-band processing is built on a state-of-the-art TC algorithm that bases it calculations on the incoming source, and that why it called source-based. A multi-band compressor, as opposed to a full band compressor, acts differently on different frequency bands. That means that each frequency band actually has its own little compressor working on it, with unique settings like threshold, ratio, attack and release. If you for instance prefer a steep compression on the lower frequencies, a soft compression on the mid frequencies, and a bright and light compression on the higher frequencies, you should use a multi-band compressor.
 
The C300 comes with several presets that are fully optimized for this kind of compression and youl be surprised to discover just how easy multi-band compression can be.
 
Based on thoughts behind parallel compression you get a completely new approach to working with compression. Now you can take a compressed signal and mix it with a dry signal and enhance all details in the music, just by turning the mix knob. What that does to the sound is that instead of pressing down the signal peaks you preserve all the higher dynamics when you play loud, and at the same time you bring out all the details from the lower end of the signal. Try and apply parallel compression on a drum kit. Youl discover that all the lower details are smack in the face, while all the bells and high dynamics of the snare and cymbals are preserved and ncompressed so to speak. And the really cool thing about it is that the C300 makes parallel or new style compression the easiest thing in the world just select the appropriate preset, and youe up and running!
 
The entire user interface has been laid out to be simple, intuitive and straightforward. All non-essential knobs and tweaking possibilities have been cut away, and replaced with innovative combinations and expansions of parameter indicators and knobs. For instance, the gate and the compressor are both controlled with the same knob, giving you improved and much faster access to important parameters.
 
The C300 gives you highly advanced TC algorithms that will process your sound with extreme precision, ultimate audio quality and outstanding performance. State-of-the-art audio converters are built in, ensuring your passage from analog to digital and back, is in the very best quality.
 
The C300 comes with a flexible routing feature that gives you all combinations of parallel and serial link modes. Stereo serial mode allows you to process a composite full-mix signal on both engines simultaneously, virtually giving you an extra device. With the C300 you can insert a stereo full-mix signal into one engine, e.g. compress it, and then send the stereo signal into the second engine, and e.g. limit it, and then send out a processed full-mix stereo signal. What that gives you is the full use of stereo processing on two serial connected engines, something that not normally attainable in this type of dynamics processor.
 
In normal dual/mono mode youl either use one engine as a compressor and the other as a gate or both engines as compressors or gates, having two individually processed mono signals coming out from each engine. Or, youl link the two engines together, and e.g. use the first engine to compress the signal, and then the second engine as a limiter, sending out a processed mono signal.
 
Features:
 
* Dual engine compressor/limiter gate/expander
 
* 16 compressor/limiter presets and 16 gate/expander presets optimized for selectable audio sources
 
* Mix features for new style compression
 
* Intelligent TC multi-band and full-band technology
 
* Detail enhancement via new style compression
 
* Flexible routing gives you all standard combinations of link modes + a stereo serial mode that virtually gives you an extra device
 
* No nonsense user interface
 
* Comprehensive metering
 
* Optimized key filters in gate mode
 
* High quality knobs
 
Retail:
 
£120-170
 
(Getting old now)
 
Used: £90-120
 
Verdict:
 
A good first cheap compressor that was well received when it first came out. But now there are better alternatives such as the Art Pro VLA and the RNC at this price. Neither notable nor anonymous.

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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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Since its introduction in the mid 1970's, the dbx 160 series has been the world's most popular line of audio compressors. After the classic 160 (which is still used daily in many world class studios), came the 165, the 160X and the 160XT. The 160X/XT were the models that truly became the industry standard. Solid construction, fool proof operation, great sound, at-a-glance metering and a bulletproof output stage all contributed to its popularity with musicians, recording studios, consultants and installers, and broadcast media production people alike.
 
The dbx® 160A is a legendary dbx® 160 family of compressor/limiters. The same classic sound, easy set-up and no compromise metering is now married to an improved signal path and stronger chassis design. The result is industry standard compressor/limiter which is digital-ready and road tough.
 
Featuring switch-selectable OverEasy® and Hard Knee compression curves along with extremely wide-ranging threshold, ratio and output controls, the dbx 160A is up to any task. True RMS level detection provides the most natural-sounding dynamics processing available, from subtle compression to "brick wall" peak limiting. Choose low ratios and OverEasy® compression to transparently smooth out fluctuating vocal and instrumental levels. Or use the 160A's Hard Knee compression and high ratios (up to and beyond :1 and over 60dB gain reduction) for bombproof protection against overload distortion in digital recording, P.A. systems and broadcast signals. The 160A is fully compatible with +4/-10dB and balanced/ unbalanced systems, and its electronically balanced output stage is an outstanding line driver for long cable runs (an output transformer is optional). The 19-segment, switchable input/ output LED metering can be easily calibrated to any operating level. 12-segment gain reduction LEDs provide precise analysis at a glance.
 
The dbx® 160A's unique "INFINITY +" inverse-compression mode actually decreases the audio output level below unity gain when the input exceeds threshold, a real lifesaver for correcting overbearing vocal choruses and controlling runaway house mix levels. A detector input can be used with an equalizer for de-essing sibilant vocals and selectively smoothing out boomy notes on acoustic guitar and bass. And two 160As can be stereo-coupled to process an entire mix or instruments mic'd in stereo, without shifting the left/right image. Its musical sound, easy operation and unequaled versatility made the original dbx® 160 a world standard. The 160A follows that tradition, while meeting the challenges of a digital world.ent in the mix, or overall characteristics of 4 independent signals or control the gain leveling on a couple of stereo pairs, the dbx 160A is for you.
 
Retail:
 
£300-400
 
Used
 
£200-£300
 
Verdict:
 
General all purpose kick and drum compressor. Valued for its "over easy" compression. Extra Notes:
 
  * OverEasy® or classic hard knee compression with dbx's® ultra-musical program dependent attack and release times
  * Compression ratio variable from 1:1 through infinity :1 to negative compression
  * Precision dual RMS LED display monitors input or putput and gain reduction over a wide range and calibrates for different operating levels
  * Over 60dB of gain reduction available
  * Exclusive Infinity+ compression allows negative compression
  * Independent balanced and unbalanced outputs can drive 600 loads to +24dBm simultaneously. New floating balanced output stage drives any load
  * Optional output transformer capable
  * Strappable with another 160A for true RMS stereo summing operation

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Retail:
 
$299 (a long time ago)
 
Used:
 
$200-300 but its going up.
 
Verdict:
 
Some opinion is divided but overall the users who like it have had the units for over 20 years and swear by them. The blue face is the prized ones and they have a characteristic sound and rugged build. Popular but could be getting rare.

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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 RNC achieves such high performance at a low cost by using evolutionary advances in digital technology, coupled with the best analog has to offer. Using digital controls and an all-analog signal path, the RNC offers accurate, precise controls and a clean tonal character.
 
The RNC provides two modes of operation: normal and SuperNice TM. Normal mode allows the RNC to be used for everyday compression tasks, like punchy snare drums or bass guitars, and is great for everything from gentle compression to serious squashing. SuperNice mode provides near-invisible signal compression for sensitive material where compression artifacts are less desirable (like vocals, acoustic guitar or the program bus).
 
In a word: transparent. The RNC yields clean, airy compression with few artifacts and little high end loss, even at massive gain reduction. This amazing performance is why many professionals are calling the RNC one of the best sounding compressors for under $2000.
 
 
Retail:
 
$199
 
£190
 
Used
 
$126-170
 
£90-120
 
Verdict:
 
Looks can deceive. A half rack compressor that has stood the test of time and proved itself a winner. Using two in serial is best for mastering on a budget with Super Nice mode on. If you've got the money to fit 2 in a rack neatly, look up the Funk Logic NCC-1701 Rack Tray kit. (Yes this is indeed the serial number of the USS Enterprise.) for around $60 / £45. Only drawback is everyone has got one. Good, professional results for an introductory hardware compressor.

The Funk Logic NCC-1701: How to hide your inferior half-rack ways and look like a serious producer.

The kit comes with knob extensions but unfortunately doesn't come with patience.

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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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