Discover the rich sound of legendary British compression with the authentic SSL 4000 G Bus Compressor — now available as both UAD Native and UAD DSP plug-ins. 

Integral to the hit-making SSL sound, the G Bus Compressor has been a secret weapon for artists like Michael Jackson on "Thriller" and modern stars like Adele on "25,"* making mixes bigger, more powerful, and punchy while enhancing cohesion and clarity. 

This iconic compressor adds the famous SSL "glue" and dynamic control to your mix, creating a unified and polished sound that stands out. With intuitive user-friendly controls, the SSL 4000 G Bus Compressor plugin makes it easy for anyone to achieve that coveted SSL sound, whether you're a seasoned pro or just starting out. 

Bring the rich, professional polish that has defined hits across generations to your own music and mixes today.

• Mix with an end-to-end emulation of the iconic SSL G Bus Compressor
• NEW! Get external sidechaining capabilities for even more dynamic control over your mixes with UAD Native version — no Apollo required
• Add classic SSL punch to your mix, instrument buses, or any source
• Harness features like Side Chain Filtering, Mix, and Headroom controls
• Mix with artist presets from Just Blaze (Beyoncé, Kendrick Lamar), Peter Mokran (The Flaming Lips, Mary J. Blige), Ian Boxill I, and more

SSL 4000 G Bus Compressor (left) and SSL G Bus Compressor Legacy (right)

Artist Presets

The SSL 4000 G Bus Compressor includes artist presets from the prominent SSL users below. Presets are accessed with the preset browser.

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SSL G Series Bus Compressor Family

The SSL G Series Bus Compressor Collection consists of two UAD plug-ins: SSL G Bus Compressor, and SSL G Bus Compressor Legacy (UAD-2 DSP only).

4000 G Bus Compressor

Developed in close collaboration with SSL engineers and prominent SSL users, UA's second-generation SSL G Bus Compressor represents the most authentic emulation of the industry standard SSL 4000 G console bus compressor (and its outboard counterparts).

Features in the newer SSL G Bus Compressor that are not in the original SSL G Bus Compressor Legacy include:

• Fully revamped algorithmic circuit model, for even greater sonic parity with the original analog hardware
• Modeled after the best available examples, with unprecedented access to SSL schematics and design insights
• Continuously variable sidechain HPF (high-pass filter) for increased control of bass-heavy mixes or subgroups
• Wet/dry mix control for parallel processing
• Headroom control for setting custom operating reference levels, offering greater flexibility

SSL G Bus Compressor Legacy

UA's original SSL G Bus Compressor Legacy plug-in was an instant hit among SSL-loving engineers, offering the very best emulation of the SSL bus compression sound available at the time.

While SSL G Bus Compressor Legacy does not include the newly revamped circuit model and the other enhancements of the newer SSL G Bus Compressor, its lower DSP usage and simple feature set continue to make it a useful tool, especially when DSP demands are high.

4K Bus Compressor

The 4K Bus Compressor plug-in was superseded by SSL G Bus Compressor Legacy, which offers feature and sonic improvements with official endorsement from SSL. 4K Bus Compressor is still included with UAD software for compatibility with older sessions.

Because 4K Bus Compressor has the same controls as SSL G Bus Compressor Legacy (exception: Auto-fade is unavailable with 4K Bus Compressor), 4K Bus Compressor does not have its own dedicated article, and its controls are documented in this article instead.

Note: 4K Bus Compressor is not included in the SSL 4000 G Bus Compressor Collection.

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Operational Overview

This section provides a general overview of SSL G Bus Compressor operational concepts. For specific individual control details, see the [SSL G Bus Compressor Controls] section later in this article.

The Master Bus Compressor

The SSL G Bus Compressor is designed with the 2-bus in mind. The control set always adjusts both the left and right channels simultaneously. The ratios, attack, and release settings are also specially tailored for bus use, and give just the right variety of options to make it useful for a wide variety of source material. Attack and release times allow the compression behavior to be 'tuned' to the tempo and feel of the song (to some degree), and the Auto setting provides a program-dependent, multi-stage release for the greatest degree of transparency. 

The 2:1 ratio can be used for the most transparent sound, 10:1 for tougher, more audible sound, or 4:1 for more moderate compression. Typically, this processor is meant to be used with minimal gain reduction. In most cases, setting the threshold for 1-2 dB average gain reduction is most common, with occasional transients that go beyond the average. In quieter passages, little or no meter movement will occur. Make-up gain can be used to get a good gain match between active and bypassed.

The SSL G is also useful on groups such as drum buses. In this case, a more aggressive approach may be appropriate, with a greater range of gain reduction. A ratio of 10:1 will give a harder sound often desired for drum groups. Fast attacks and releases will give the most audible sound of the compressor working.

Mixing To the Compressor

Traditionally, the SSL G is most commonly used from the beginning of the mix process, and the engineer is "mixing to" the sound and behavior of the compressor. The ideal way to audition this plug-in is on a new mix, dropped into an insert on your stereo master channel. In this case, you will be spending a lot of time keeping an eye on gain reduction metering and you may make tweaks to the setup as the mix progresses. Of course it can also be dropped into existing mixes at any time, but keep in mind it may take a bit more effort to dial in, especially if your ear is already used to the sound without its compression properties.

Variable-Knee Compression

The "knee" point of the compressor, set with the THRESHOLD control, purposely changes depending on the setting of the RATIO control. Decreasing the RATIO setting lowers the effective threshold, hence maintaining the perceived "loudness" of the compressed signal.

Dominant Sidechain Architecture

The SSL G Bus Compressor features a classic "dominant" sidechain configuration. The left and right signals are independently rectified and compared in real time, and the dominant (louder) channel controls the amount of gain reduction for the overall stereo signal.

Dynamics External Sidechain

You can sidechain from a track in your DAW to the dynamics section of the SSL G Bus Compressor native plug-in. See Using an External Sidechain with UAD Plug-Ins for details. 

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SSL 4000 G Bus Compressor Controls

Threshold

Threshold defines the signal level at which the onset of compression occurs. Incoming signals that exceed this level are compressed. Signals below the level are unaffected. The control range is ±15 dB.

As the Threshold control is decreased and more compression occurs, output level is typically reduced. The Make Up control can be used to modify the output to compensate if desired.

Note that the Ratio control interacts with the compression threshold to maintain the perceived loudness of the signal. As Ratio is decreased, the effective threshold is lowered.

Tip: In SSL Bus Compressor, click the "0" text label to return Threshold to its center position. 

Make Up

Make Up (post-compression make up gain) controls the signal level that is output from the plug-in. The range is 0 dB to +15 dB.

Generally speaking, the Make Up control is adjusted after the desired amount of compression is achieved with the Threshold and Ratio controls. Make Up does not affect the amount of compression.

Tip: In SSL Bus Compressor, click the "0" text label to return Make Up to its unity position. 

Attack

Attack sets the amount of time that must elapse once the input signal reaches the Threshold level before compression is applied. The faster the Attack, the more rapidly compression is applied to signals above the threshold. Available Attack times are discrete values of 0.1 milliseconds, 0.3 ms, 1 ms, 3 ms, 10 ms, and 30 ms.

Release

Release sets the amount of time it takes for compression to cease once the input signal drops below the threshold level. Slower release times can smooth the transition that occurs when the signal dips below the threshold, especially useful for material with frequent peaks. However, if the Release time is set too long, compression for sections of audio with loud signals may extend to lengthy sections of audio with lower signals.

Available Release times are discrete values of 100 ms, 300 ms, 600 ms, 1.2 s, and Auto. The Auto release characteristic for SSL G Bus Compressor has a unique quality that is optimized for program material.

Ratio

Ratio defines the amount of gain reduction to be processed by the compressor. For example, a value of 2 (expressed as a 2:1 ratio) reduces the signal above the threshold by half, with an input signal of 20 dB being reduced to 10 dB. The available Ratio values are 2:1, 4:1, and 10:1.

Tip: The Ratio control interacts with the compression threshold so the perceived loudness of the signal is maintained. As Ratio is decreased, the effective threshold is lowered.

Power (IN)

The Power button determines whether the plug-in is active. Click the Power button to toggle the processor state. Power is useful for comparing the processed sound to that of the original signal.

Gain Reduction Meter

The VU-style Gain Reduction meter displays the amount of gain reduction occurring in the compressor. Higher values indicate more gain reduction.

Increase the signal level into the plug-in and/or lower the Threshold control to increase gain reduction. The Headroom control also affects the amount of gain reduction.

Sidechain Filter

Amongst some circles of SSL aficionados, the saying went, "If your bottom-end makes the G Bus Compressor pump, you've got too much bottom." That said, not every mix or subgroup is created equal, so we added a continuously variable 12 dB per octave high-pass filter to the internal sidechain of the SSL G Bus Compressor. The sidechain filter allows removal of low-frequency content from the control sidechain, reducing excessive gain reduction and/or "pumping" on bass-heavy audio signals without reducing bass content of the audio signal itself.

Note: The Sidechain Filter only acts on the sidechain signal. While it can produce an audible change in dynamics behavior, it does not act directly on the signal that is output from the plug-in.

At the lowest setting of the SC Filter control, the filter is defeated, and does not impact compressor behavior. As the SC Filter knob is turned clockwise, the filter is engaged and its frequency sweeps between 20 Hz – 500 Hz, allowing for a wide range of relationships between bass level and gain reduction.

Tip: Click the OFF text label to turn off the sidechain filter. Click OFF again to return the filter to its previous setting.

Note: Sidechain Filter is not available on SSL G Bus Compressor Legacy or 4K Bus Compressor.

Headroom

The Headroom control, which is a UAD-only feature not found in the original hardware, enables adjustment of the internal operating reference level for the SSL G Bus Compressor. Headroom enables best practice operating level matching, or it can be used creatively to expand the sonic range of the processor. By fine-tuning Headroom, the non-linear I/O distortion and compression response characteristics can be tailored independently of signal input levels. By increasing the Headroom (by rotating the control counter-clockwise), signals at the input can be pushed higher before they compress.

Headroom simply changes the internal operating level so that the plug-in is not "pushed" into gain reduction as much. Headroom can be set (in dB) to 4, 8, 12, 16, 20, 24, or 28. The default value is 16 dB (when the set screw "dot" is in the straight up 12 o'clock position). Note that Headroom is increased as the dB value decreases. 

Tip: Click the "HR-dB" text label to return the control to its default value. 

At higher dB values (clockwise rotation), signals push the plug-in into gain reduction (and more non-linearity and "good" harmonic distortion color) more easily. Set the control to a lower value (counter-clockwise rotation) when less gain reduction and less color is desired. 

Note: To avoid the temporary gain increases that can result when adjusting Headroom, automating this control is not recommended. 

Keep in mind there are no hard and fast headroom rules. Feel free to experiment with the various positions of the Headroom control regardless of the audio source. If it sounds good, use it!

Note: Headroom is not available on SSL G Bus Compressor Legacy or 4K Bus Compressor.

Mix

The output balance between the signal processed by the plug-in and the original dry source signal can be adjusted with the Mix control. Mix facilitates parallel compression techniques without having to create additional routings in the DAW.

When set to 0, only the unprocessed source signal is output. When set to 100 (the default value), only the processed signal is output. When set to the center position (50%), an equal blend of both the dry and wet signals is output (parallel compression). The balance is continuously variable throughout the control range. 

Tip: Click the 50 text label to quickly set the control to the 50% position. Click the 0 text label to set the control to the minimum position. Click the 100 text label to set the control to the maximum position.

Note: Mix is not available on SSL G Bus Compressor Legacy or 4K Bus Compressor.

Auto Fade

As found on the console and favorite SSL outboard units, the Auto Fade function is useful when the end of a song needs a gradual decrease in volume. The speed of the fade can be tuned from 1 to 60 seconds, and incorporates SSL's signature fade curves. 

The SSL G Bus Compressor plug-in provides an Auto Fade function that, upon activation, automatically reduces the plug-in output to minimum within a specified time period. This function enables extremely smooth-sounding fade-outs (and fade-ins). As a plus, it can be automated as well.

The Auto Fade function processes the signal at the output of the compressor. The fade signal level that is output has an exponential curve.

Note: Auto-Fade is not available in 4K Bus Compressor.

Rate

The Rate control determines the amount of time that passes between the Auto Fade button being activated and the plug-in output level being reduced to minimum (or being raised to 0 dB in the case of a fade-in). The available range is from 1 second to 60 seconds.

Fade times immediately reflect the current Rate value. Therefore a fade-out that has already been initiated can be accelerated by changing Rate during the fade-out. Conversely, a fade-in can be accelerated by changing Rate during the fade-in.

Auto Fade Button

Activating the Auto Fade button initiates a fade-out. The fade-out time is determined by the Rate setting. The Auto Fade button flashes when a fade-out is in progress, and is continuously lit when the fade-out is complete (when the Rate time has elapsed).

Deactivating Fade (clicking the solid-lit button) initiates a fade-in. During a fade-in, the signal level is increased from the current level of attenuation to 0 dB of attenuation. The Auto Fade button flashes when a fade-in is in progress, and is no longer lit when the fade-in is complete (when the Rate time has elapsed).

Toggling the Auto Fade button causes an already active fade to reverse direction, without a jump in output level. The Rate is constant even if an active fade is interrupted. For example, if the Rate value is 30 seconds and a fade-out is initiated, then Auto Fade is clicked again after 20 seconds, it will take 20 seconds to fade back in. 

Tip: Shift-click the Fade button to instantly return the level back to 0 dB (this feature cannot be automated).

*Use of artist names does not constitute official endorsement of the software. 

All visual and aural references to the SSL 4000 E series and all use of SSL trademarks are being made with written permission from Solid State Logic. Special thanks to Jim Motley and Chris Jenkins.