SONALKSISSV-315 CompressorSV-517 Equalizer(Mac/Win)

British software manufacturer Sonalksis is a young company, but its four founding members are former R&D engineers for AMS-Neve, purveyor of high-end
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British software manufacturer Sonalksis is a young company, but its four founding members are former R&D engineers for AMS-Neve, purveyor of high-end analog gear. That foundation in analog-circuit design formed the basis for the company's first two DAW plug-ins, SV-315 Compressor and SV-517 Equalizer. Both plug-ins use modeling to replicate in the digital domain the characteristics of analog signal processors designed by Sonalksis' engineers.

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FIG. 1: SV-315 has two choices of compression curves (settings I and II). Crush and Hold knobs and a limiter section control the treatment of transients. Alternative sidechain-filter buttons are located below the Crush and Hold controls.

Zero-latency throughput for both plug-ins permits use while tracking (as long as you can set your host's buffer setting low enough to preclude a delayed monitoring path). Other applications include mixing and mastering. Both plug-ins support standard sampling rates from 44.1 to 192 kHz and ship in mono and stereo versions. The plug-ins support VST (Mac OS 9/X and PC), DirectX (PC), and Audio Units (OS X). RTAS support on both platforms is planned and may be available by the time you read this review.

You can download the plug-ins from the Sonalksis Web site or order boxed CD versions. You'll need a valid email account to receive the registration-key files (one for each plug-in) that are needed to unlock the plug-ins for unrestricted use.

SV-315 Compressor

SV-315 Compressor comprises a compressor and a limiter chained in series. SV-315's graphical user interface (GUI) has continuously variable controls for setting the compressor's threshold, ratio, knee, and attack and release times. There is also a program-sensitive auto-release function. The ratio control has a working range from 1.5:1 to 10:1. You can adjust the knee to be exceedingly soft, causing the gradual onset of compression as low as 30 dB below the threshold. (The threshold can be set as low as -48 dBfs).

SV-315's compressor section allows for classic and contemporary compression curves by giving the user a choice between two modeled attack-and-release circuits (see Fig. 1). A Crush control modifies how easily the compressor's gain-control element will saturate; lower settings let more transients through unprocessed. A Hold control — available only when the plug-in's auto-release function is activated — leaves transients progressively more intact as the Hold value is raised. SV-315's sidechain can use any of four different filter settings.

To the Limit

SV-315 has a separate limiter circuit, which can be bypassed and which has its own LED-style indicator that lights progressively brighter with increasing amounts of limiting. The limiter can be switched to exhibit either a fast or a slow release time. Bypassing the limiter and closing the plug-in window conserves CPU resources, allowing for more instantiations.

A switchable auto-gain function automatically provides compressor make-up gain before the limiter section. SV-315's auto-gain feature can sometimes cause “overs” if the limiter section is not active. There are controls for master (post-limiter) output level (with associated metering and peak-hold Over indicator) and global bypass, as well as a Reset button, which returns all SV-315 controls to default values. As much as 24 dB of compressor makeup gain and ±24 dB of post-limiter gain or attenuation are possible.

An interactive graphical display illustrates SV-315's combined compression-and-limiting curve and gives you handles that you can move to adjust compressor and limiter thresholds and compressor makeup gain; unfortunately, the compressor makeup gain parameter lacks a numeric readout. The gain-reduction meter below the graphical display shows the combined total gain reduction from the compressor and limiter sections.

While My Guitar Gently Gets Squashed

SV-315 sounded awesome on electric guitar blowing through a Roland Micro Cube amp miked with a Royer R-122. With a 6:1 ratio and very soft knee dialed in, the differences between SV-315's classic and contemporary compressor settings were subtle yet quantifiable: the classic setting sounded slightly warmer, whereas the contemporary setting was more open and airy. Both settings sounded decidedly analog and not what I expect from most digital compressors. Putting the limiter section in the circuit and turning up the Crush control put a tight lid on transients, creating an in-your-face sound that was dynamite. Boosting SV-315's Hold control a little bit seemed to choke the sound and make it pump, but fortunately the Hold control can be defeated.

In other tests, SV-315 gave an electric-bass track more weight, fullness, and authority. Compressed lead vocals sounded warmer and stronger than the original. But on stereo drum overheads, I couldn't get the classic Led Zeppelin sound that I was looking for — a 10:1 ratio caused hi-hat hits to leap out of the mix regardless of the attack and release settings used and with 12 dB of gain reduction on peaks (even with Crush maxed).

SV-517 Equalizer

Six widely overlapping bands of EQ are provided in the SV-517 plug-in. The highest and lowest bands offer variable-slope (0-, 6-, 12-, or 24 dB/octave) lowpass and highpass filters, respectively. The four middle bands are fully parametric bell-curve filters, but the lowest and highest of those bands can be independently switched to give you low- and high-shelving EQ, respectively. Three styles of parametric bell-curve filters and two types of shelving filters can be globally selected for their respective filter types (see Fig. 2).

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FIG. 2: SV-517 offers two types of global, analog-style shelving filters. Setting I (top) produces a prominent dip in response at the transition and corner frequencies. Setting II sports a less prominent dip at the transition and produces a resonance (boost) at the corner frequency.

Each band has its own frequency control that sets the center frequency for bell-curve response or corner frequency for shelving, highpass, or lowpass filter response. Each of the four middle bands has a gain control (giving you as much as 18 dB of boost or cut), a bypass button, and a Q control. When either the low- or the high-frequency filter is set to shelving response, its Q control adjusts the steepness of the filter's slope. Bypassing individual bands or closing the plug-in window conserves CPU resources and allows for more instantiations.

Global Issues

Global controls include a master bypass button and a gain control. The latter boosts or cuts the plug-in's output level as much as 24 dB and has LED-ladder-style metering and a peak-hold Over indicator. Clicking on the Flat button resets all filter gain controls to zero (no boost or cut) and turns off the highpass and lowpass filters, while retaining all other equalizer settings as a baseline for renewed tweaks.

An interactive x-y graph (showing frequency versus gain) displays the user-adjusted frequency response of the equalizer. You can tweak the equalizer by clicking on and dragging the graph's various handles.

SV-517 is one of the most euphonious digital equalizers I've heard, with a character that sounds surprisingly like high-end analog EQ. Lows are tight and robust, mids are clear and sweet, and highs are silvery smooth. SV-517's interface is a joy to work with — it gives you a wealth of intuitive controls. Having the ability to simultaneously work with shelving filters and highpass and lowpass filters gives tremendous flexibility in a variety of equalization applications. No matter what I threw at SV-517 — including vocals, electric bass, acoustic guitar, kick drum, and full mixes — it always sounded great.

Common Ground

Thanks to the sky-high headroom that their 64-bit floating point internal processing provides, the plug-ins don't need an input-gain control to prevent clipping. Output levels, however, can clip if the usual precautions aren't taken. Mac users can Command + click (Control-click with a PC) on the Over indicator in either plug-in's GUI to automatically trim output level(s) just enough to prevent clipping — a great timesaving feature. You must click on the Over indicator before its peak-hold time expires, however, which usually precludes using that function to tweak headroom after a mix has run through to the end of the song. Furthermore, that headroom function attenuates only signals that are clipping; it cannot add makeup gain to bring weak output levels up to 0 dBfs. The plug-ins' output-level meters don't have numeric readouts, and they top out a few decibels above 0 dBfs, making manual adjustments more difficult. Those are all fairly minor issues.

Many of the controls in both plug-ins' GUIs have numeric readouts to guide your edits. You can click and drag on the readouts to edit their values. Both plug-ins give you buttons for setting up useful A/B comparisons or for automating switching between two different control setups. Automating both plug-ins' various controls — including global bypasses — in Digital Performer (DP) v4.52 was a breeze.

Efficiency Experts

SV-315 and SV-517 are efficient — with three instantiations of each plug-in (six total) running in DP v4.52, only approximately 25 percent of my dual 867 MHz G4's CPU resources were consumed. The plug-ins' global bypass buttons worked completely glitch free, without introducing any dropouts or pops. Both plug-ins have useful presets, but they aren't graphically checked when you choose them, forcing you to sometimes guess at which preset is currently in use.

Sonalksis's SV-315 and SV-517 deliver convincing emulations of analog processing. Neither plug-in sounds completely transparent or precise, but that's not their raison d'etre. If you're looking for that elusive analog sound in the digital domain, these plug-ins deliver the goods with finesse.

EM contributing editor Michael Cooper is the owner of Michael Cooper Recording, located in beautiful Sisters, Oregon.


SV-315 Compressor

compressor software plug-in


PROS: Smooth, analog-like sound. Multiple compression models. SV-315 features independent limiting and four sidechain filters.

CONS: Hold mode causes pumping. No numeric readout for makeup gain. Minimum attack time is too slow. Automatic headroom adjustment is available only during the peak-hold interval.


Sonalksis/GSF Agency (distributor) or


SV-517 Equalizer

equalizer software plug-in


PROS: Smooth, analog-like sound. Multiple filter models. Allows simultaneous shelving, highpass, and lowpass filtering. Toggling of individual EQ bands.

CONS: Automatic headroom adjustment is available only during the peak-hold interval.


Sonalksis/GSF Agency (distributor) or