ART CS2 Two Channel Compressor/Limiter/Gate User's Guide
Introduction
Thank you for purchasing the ART CS2 Two Channel Compressor/Limiter/Gate. This unit is designed to provide sophisticated audio signal processing for recording, sound reinforcement, and live performance. It offers extensive control over dynamics and sound quality, comparable to units costing significantly more, through a user-friendly interface.
Features
- Two independent compressor/limiter/gates
- Stereo-linked or dual-mono operation
- Detector loop on each channel for side-chain processing
- Balanced or unbalanced operation for inputs and outputs
- Soft- and hard-knee compression for flexibility
- Bypass switch for each channel
- Input and output level LED monitors
- Limit/compressor selector on each channel
- Gate has threshold and release controls, and threshold LED
- Gain reduction LED display for each channel
- All-steel enclosure
- Designed and manufactured in the United States of America
Front-Panel Controls & Indicators
Both channels of the CS2 operate identically. The Stereo-Link/Dual-Mono switch is discussed separately.
Threshold
Sets the point at which incoming signals are compressed or limited. Turning clockwise raises the threshold, requiring higher signal levels for compression. The range is -40dBu to +20dBu.
Below & Above LEDs
Two LEDs indicate signal status relative to the threshold. The 'Below' LED glows yellow when the signal is below the threshold. The 'Above' LED glows red when the signal exceeds the threshold, indicating compression or limiting is active.
Slope
Determines the compression ratio, controlling how much the signal level is reduced once it crosses the threshold. Ratios range from 1:1 (no compression) to ∞:1 (limiting). Settings between labeled points (1:1, 4:1, ∞:1) offer intermediate ratios like 2:1, 2.5:1, 7:1, and 12:1.
Attack
Sets how quickly the CS2 responds to incoming signals that exceed the threshold. Time ranges from 0.5ms to 50ms. Faster attack times can reduce impact, while slower times preserve more natural dynamics.
Release
Determines how long it takes for the compressor to return to unity gain after the signal falls below the threshold. Time ranges from 50ms to 2 seconds. Shorter release times are suitable for percussive sounds, while longer times work well for sustained instruments.
Gain Reduction LED Display
A 10-LED display showing the amount of gain reduction applied by the compressor, with each LED representing approximately 3dB of reduction.
Soft/Hard Knee Response Selector
Selects the compression curve. 'Hard Knee' provides an abrupt change in compression at the threshold, suitable for limiting or aggressive effects. 'Soft Knee' offers a more gradual transition, ideal for subtle dynamic control and musical applications.
Limit/Compress Selector
A switch that configures the circuitry for either compression or limiting. When set to 'Limit' (depressed), the Slope is automatically set to ∞:1, and the Attack time is set to its fastest setting.
Output Level
Adjusts the output signal level to compensate for gain reduction or to match downstream equipment. The range is -20dB to +20dB.
Level LED Meter
A six-LED meter that displays either the input or output signal level, selectable via the Input/Output Monitor Selector. Levels are indicated in 5dB increments from -30dB to +5dB.
Input/Output Monitor Selector
Allows the user to switch the Level LED Meter between monitoring input and output levels, facilitating comparison and adjustment of the Output Level control.
Bypass/Compressor Selector
A switch to bypass the compressor and noise gate circuitry, allowing the signal to pass directly from input to output. This is a hardwired bypass, functional even without power.
Noise Gate
A circuit designed to mute audio signals that fall below a set threshold, useful for controlling background noise or microphone bleed. It features Threshold and Release controls.
Gate Threshold
Sets the level at which the noise gate opens. It should be set just above the ambient noise floor.
Gate Release
Controls the time it takes for the gate to close after the signal drops below the threshold. Gradual settings are recommended for most musical applications.
Gate LED
Indicates when the noise gate is active, meaning the signal is below the threshold.
Stereo-Link/Dual-Mono Selector
Links Channel 1 and Channel 2 for stereo operation, duplicating Channel 1's settings to Channel 2. In this mode, Channel 1 acts as the master, and Channel 2's compressor controls are disabled.
Rear-Panel Inputs & Outputs
The rear panel provides connections for each of the two channels.
Power Input
A DC input jack for the included AC adapter. Use only the provided adapter to avoid damaging the unit.
Line In
1/4" TRS jacks for connecting balanced or unbalanced line-level sources. Can be used with standard 1/4" TS or TRS cables.
Line Out
1/4" TRS jacks for outputting balanced or unbalanced line-level signals to other equipment. Can be used with standard 1/4" TS or TRS cables.
Detector Loop
1/4" jacks for side-chain processing, commonly used for applications like 'ducking' (lowering music volume when speech is present) and 'de-essing' (reducing sibilance).
Applications
The CS2 can be used in various audio scenarios.
Suggested Initial Settings
The following are starting points for compression ratios based on sound source type:
| Type Of Sound Source | Slope (Ratio) |
|---|---|
| Vocals | 2:1, 3:1, or 4:1 |
| Bass | 4:1 or 6:1 |
| Heavy electric guitar | 3:1, 4:1, or 6:1 |
| Light fingerpicked acoustic guitar | 2:1 or 3:1 |
| Strings, horns, or synthesizers | 3:1 or 4:1 |
| Slap bass | 6:1 to 10:1 (or limit) |
| Overhead percussion | 2:1 to 6:1 |
Suggested Attack and Release times:
- Fast: Quickest setting to 9 o'clock
- Medium: 10 o'clock to 1 o'clock
- Slow: 2 o'clock to slowest setting
Using The CS2 For Ducking
To achieve ducking (e.g., lowering music volume when a vocalist speaks), patch a sound source (like a tape player or mixer output) into the CS2's Line In. Connect the CS2's Line Out to a mixer's line input. Then, send a microphone's signal (via a preamp or mixer) to the CS2's Detector Loop. Adjust the CS2's compression to lower the music level when you speak into the mic. The mixer is then used to balance the mic and music levels. For stereo operation, link the two CS2 channels.
Diagram Description: Shows a mixer output connected to CS2 Line In, CS2 Line Out to mixer input, and a microphone signal routed through a preamp/mixer to the CS2 Detector Loop.
Using The CS2 For Vocal De-Essing
To reduce sibilance ('S' and 'T' sounds) in vocals, connect a microphone to a mixer. Send the mixer's channel insert loop out to the CS2's Line In, and the CS2's Line Out to the mixer's insert loop return. Use a TRS-to-dual-mono Y-cord to connect a graphic equalizer's line in and out to the CS2's Detector Loop. Set the CS2 to compress and boost a frequency band (typically 2kHz-10kHz) on the EQ to target sibilant sounds. This process can be done for two channels independently with two EQs.
Diagram Description: Shows a microphone connected to a mixer, with the mixer's insert loop out going to CS2 Line In, CS2 Line Out returning to the mixer, and the CS2 Detector Loop connected to a graphic equalizer which is then connected back to the Detector Loop. A frequency response graph is also shown.
Using The CS2 To Manage Vocal Levels
To control vocal dynamics, connect a microphone's signal via a mixer's insert loop: Mixer insert loop out to CS2 Line In, and CS2 Line Out to mixer insert loop return. Adjust the CS2 settings to suit the musical application. Both channels can be used simultaneously.
Diagram Description: Shows a mixer's insert loop send connected to CS2 Line In, and CS2 Line Out connected to the mixer's insert loop return.
Using The CS2 To Add Sustain
For adding sustain, particularly to guitars, patch the CS2 into an amplifier's pre-EQ effects loop. Alternatively, connect the guitar directly to the CS2's Line In, and the CS2's Line Out to an amplifier or signal processor. Ensure the signal source has sufficient output level (e.g., high-output pickups, active electronics) to avoid a poor signal-to-noise ratio. Adjusting the compressor's attack and ratio can enhance note sustain.
Diagram Description: Shows a guitar connected to CS2 Line In, and CS2 Line Out connected to an amplifier's effects loop send/return or directly to the amplifier input.
Using The CS2 To Protect Signal Processors From Overload
To prevent signal processors (like vintage effects units) from distorting due to hot signals, connect a mixer's effects send or preamp's line out to the CS2's Line In. Connect the CS2's Line Out to the signal processor's line in. The signal processor's output then connects back to the mixer or amplifier. Setting the CS2 to compress or limit will keep excessive levels from overloading the processor.
Diagram Description: Shows a mixer effects send or preamp output connected to CS2 Line In, CS2 Line Out connected to a signal processor's line in, and the signal processor's output connected to a mixer effects return or amplifier.
Using The CS2 As A Limiter For Bass Guitar
To manage the dynamic range of bass guitar, especially during slapping techniques, connect the bass into a mixer. Send the mixer's channel effects send to the CS2's Line In, and the CS2's Line Out to the mixer's effects return. Soft-knee compression is suitable for occasional slaps, while limiting is recommended for percussive styles. The CS2 can also be used in an onstage rig to protect speakers by limiting the signal sent to the power amplifier.
Diagram Description: Shows a bass guitar connected to a mixer, with the mixer's effects send going to CS2 Line In, and CS2 Line Out returning to the mixer's effects return. An alternative setup shows a preamp output connected to CS2, and CS2 Line Out to a power amp.
Using The CS2 As A Limiter To Protect Speakers
To prevent speakers from being damaged by sudden loud transients, connect a mixer's line out to the CS2's Line In, and the CS2's Line Out to a power amplifier's input. Setting the CS2 to limit will reduce sudden peaks. This can be applied to main P.A. systems and monitors, or across stereo channels for left/right speaker protection. Multiple CS2 units can be used on crossover outputs to independently limit different frequency ranges.
Diagram Description: Shows a mixer line out connected to CS2 Line In, and CS2 Line Out connected to a power amplifier input.
Using The CS2 To Compress/Limit When Sampling
To improve the signal-to-noise ratio and headroom when sampling, connect a sound source (e.g., microphone, CD player) through a mixer to the CS2. Connect the mixer's line out to the CS2's Line In, and the CS2's Line Out to the sampler's line in. Compressing or limiting the signal before it reaches the sampler can yield better results. Use both channels of the CS2 for stereo sampling.
Diagram Description: Shows a mixer line out connected to CS2 Line In, and CS2 Line Out connected to a sampler's line in.
Understanding Compression, Limiting, and Noise Gating
How Compression Works
A compressor is a variable-gain amplifier that monitors incoming signal levels and adjusts gain to control dynamic range. The Threshold sets the activation point, and the Slope determines the compression ratio (e.g., 4:1 means a 4dB input increase results in a 1dB output increase). Attack time controls how quickly the compressor reacts, and Release time controls how long it takes to return to unity gain. Proper settings are crucial for a natural sound; incorrect settings can lead to 'pumping' or 'breathing' artifacts.
Diagram Description: Illustrates input signal levels increasing and the resulting limited signal level increasing by a smaller amount (1dB for a 4:1 ratio), showing the effect of compression.
How Limiting Works
Limiting is an extreme form of compression where the output level is prevented from increasing beyond a set point, regardless of input level changes. It's used to protect speakers from overload and prevent tape saturation. Setting the Threshold and Output controls correctly ensures that input levels do not exceed the desired maximum output level.
Diagram Description: Shows input signal increasing significantly, but the limited signal only increasing by 1dB, illustrating the hard ceiling effect of limiting.
Compression And Noise
Compression reduces dynamic range, making quiet passages louder. If the original signal contains noise (hiss, hum), compression will amplify this noise along with the desired signal. To mitigate this, ensure all equipment preceding the compressor is as quiet as possible. Placing the compressor before noisy effects like wah-wah pedals is also recommended.
Diagram Description: Shows a graph with 'Loudness' on the vertical axis and 'Duration' on the horizontal axis. It depicts a 'Signal' waveform and a 'Noise' waveform. When compressed, the noise becomes more apparent in the quieter parts of the signal.
Soft Knee and Hard Knee
Hard Knee compression activates abruptly once the signal crosses the threshold, creating a sharp change in the compression curve. Soft Knee compression offers a more gradual transition, with compression increasing progressively as the signal approaches and exceeds the threshold. Soft knee is generally considered more musical and suitable for less drastic dynamic control.
ART CS2 Specifications
| Parameter | Specification |
|---|---|
| Frequency response | 10 Hz to 40KHz ±0.5dB |
| Input impedance | 20K ohms (balanced) |
| Maximum input level | +21dBu |
| Output impedance (balanced) | 600 ohms |
| Output impedance (unbalanced) | 300 ohms |
| Maximum output level (balanced) | +27dBu |
| Maximum output level (unbalanced) | +21dBu |
| Distortion | <.009% @ 1KHz typical <.03%, 20 Hz to 20KHz |
| Noise | -97dBu @unity gain -108dBu @ gate on (independent of output level) -101dBu Equivalent Input Noise |
| Dynamic range | 117dB unweighted |
| Crosstalk | >120dB "A" weighted |
| Country of manufacture | <-85dB @ 1KHz U.S.A. |
ART reserves the right to make changes in design or specifications without notice.
Designed and manufactured in the United States of America.
Applied Research & Technology
215 Tremont Street
Rochester, NY 14608
(585) 436-2720
(585) 436-3942 (FAX)
Warranty & Service Information
Limited Warranty
Applied Research & Technology, Inc. (ART) warrants the product and its components to be free from defects in workmanship and materials for one year from the date of purchase. ART will repair or replace, at its option, defective products delivered prepaid to the factory service department or an authorized service center, accompanied by proof of purchase. This warranty excludes damage from misuse, abuse, or unauthorized alterations. The serial number must not be defaced or removed.
ART may make design changes without obligation to apply them to previously manufactured products. ART is not liable for consequential damages; some states may not allow this limitation.
For units purchased outside the United States, service is provided by authorized distributors.
Service
If your unit requires service:
- Verify the unit is the cause of the problem. Check power, connections, and cables.
- If the unit is at fault, document the problem (how and when it occurs).
- Call the factory for a Return Authorization (RA) number.
- Pack the unit securely in its original carton or a suitable substitute, placed inside another shipping box. Clearly print the RA number under the address.
- Include: return shipping address (no P.O. Boxes), copy of purchase receipt, daytime phone number, and problem description.
- Ship to: APPLIED RESEARCH & TECHNOLOGY, 215 TREMONT STREET, ROCHESTER, NY 14608, ATTN: REPAIR DEPARTMENT, RA # [Your RA Number].
- Contact customer service at (585) 436-2720 for RA numbers or repair questions. Customer Service hours are 9:00 AM to 4:00 PM Eastern Time, Monday through Friday.
Customer Service
ART's Customer Service Department is available Monday through Friday, 9:00 AM to 4:00 PM Eastern Time, to answer technical questions and provide service information.
ART CS2 Block Diagram
The block diagram illustrates the signal flow through the CS2. It shows two identical channels, each featuring balanced inputs, detector loops, and outputs. Key processing stages include compression and gating, controlled by parameters like Threshold, Release, Slope, and Attack. Indicators such as the Gain Reduction Meter, Gate LED, and Above/Below LEDs are depicted. Switches for Stereo/Mono operation and Bypass are shown in their default 'out' positions.
