elysia alpha compressor and niveau filter

by Paul Vnuk Jr.
Recording Magazine (USA) – May 2011

elysia is a German designer of seriously high-end signal processors, all with small letters in their names and non-small price tags, from $5000 for the mpressor and museq to a cool ten grand plus for the mastering-grade alpha compressor.

Luckily for us mere mortals, the good folks at elysia have teamed with the circuit-modeling experts at Brainworx to create plug-in versions of their hardware. Let’s check out the software alpha compressor.

Features and layout

The alpha compressor (both hardware and software) is a stereo compressor that is optimized for mastering purposes, with features like true Mid-Side (M/S) compression, sidechain filters, soft clip limiting, a warmth circuit, parallel compression, and a unique EQ section called the niveau filter, which is also available on its own in plug-in format.

The plug-in layout mirrors the hardware’s: clean and Euro-stylish. A large round stereo gain reduction meter dominates the center of the unit, which also contains buttons for global bypass, M/S mode, and channel linking for stereo vs. dual mono use.

Each of the two channels has three rows of matching controls. The top row has Threshold, Attack, Release, and Ratio, and buttons for choosing feed forward or feedback compression, as well as auto fast attack and release. The second row has controls for the niveau filter and sidechain, and the last row offers controls for Mix, Gain, Soft Clipping, and Warmth.

The plug-in package also includes a single-channel version that’s useful for standard channel compression—essentially one half of the mastering version, minus the filter and soft clipping features.

Two sides: the mid one and the chain one!

A recent trend in mastering is to use EQ and compressors in a Mid/Side mode, applying compression and filtering to the mono/center information independently from the side/stereo information. I used this on a few stereo mixes and it was a really cool way to tighten up and bring out the stereo field while still sounding natural and controlled.

The alpha compressor’s sidechain is the most full-featured that I have seen in hardware or software. In most modern compressors, the sidechain is typically a glorified highpass filter that allows low-end information to pass through the unit without triggering the compressor, but the alpha’s sidechain is closer to placing a proper external EQ in a compressor’s sidechain input—it offers a choice of highpass or lowpass filtering, so in essence you can compress only the high end of a mix or just the lows.

Compression tricks

The alpha’s compression is mastering and bus-centric, an ultra-fast soft-knee style whose highest ratio is 2:1. Its flexibility is expanded with a number of well-chosen features.

First, this compressor offers two modes, feed forward and feedback. Switching from the alpha’s default feedback mode to feed forward changes both the compressors’ ratios to almost double, so you can get closer to a 4:1 compression, and alters the attack. To my ears, in this mode the alpha becomes a touch more “grabby and gooey” vs. “smooth and gluey” (Don’t you love technical terminology?).

Both the Attack and Release settings feature a button known as Auto Fast, that engages a semi-automatic program-dependent behavior.

On the hardware model there’s a button labeled Transformer, which when pressed adds a custom transformer into the signal chain. The plug-in’s Warmth button adds a slight warm harmonic tone to the sound. It is a subtle effect.

Soft clipping is an ultra fast-limiter circuit that smooths out quick transient material much like tape saturation, but again is still clean and subtle; it reminds me of a well mannered cousin of UAD’s Fatso Plug-in.

niveau filter

Finally there’s the niveau filter. It’s essentially like the single bass/treble knob on an old car stereo: clockwise boosts treble, counter clockwise highlights bass. This filter’s interesting twist is that as one set of frequencies comes up, the opposing frequencies go down. While this idea has been explored in the famous Baxandall EQ curves (as represented in the Dangerous Music BAX EQ) and in the Bass and Presence functions on the Brainworx bx_digital V2, elysia has taken it to extremes.

Frequency-wise it’s continuously variable from 26 Hz to 2.2 kHz, and when the X10 button is engaged the sweep covers 260 Hz to 22 kHz. At its most extreme settings, it turns into a highpass or lowpass filter. This lets you sculpt the tone through the alpha compressor in a variety of musical and beautiful ways.

Just on its own, the niveau filter is great for everything from subtle presence tweaks, rounding off harsh highs or lows, to freaky lo-fi effects and cuts like the old speaker/telephone trick... and it’s automatable so you can morph between all of the above. Even as just a set of HP/LP filters, it’s exceptional to have around.

And why not? Not only is it available as a feature of the alpha compressor, but it’s also downloadable from the good folks at elysia as a standalone plug-in... and they’re offering it for free!

In use: performance and power

The alpha compressor’s realism is due in part to its high level of oversampling, but that realism comes at a price. On my 2.5 GHz Core 2 Duo Macbook Pro with 2 GB of RAM in Cubase, I was only able to run 6 mono alpha compressors and one master stereo version before it pegged the VST performance meter and caused clicks and pops. Now admittedly this is a 5 year old laptop, but not all of us have the newest hardware, so keep this in mind.

Sonically the alpha is in the ultra clear hi-fi category; it adds control without altering your sound. Even in the more aggressive feedforward mode, it retains the sonic signature of the source material and stays out of the way. This thing does ‘subtle’ so well it’s scary. It’s the kind of compressor where you’re not sure what it’s doing until you bypass it... and then you realize it’s doing a lot, beautifully, without being heavy-handed.

You don’t need an iLok for the 14-day demo version, and the niveau filter is free from start to finish. Go grab these plug-ins and get ready to be very elegantly amazed!