elysia alpha compressor plugin review

by Ludvig Nylund
Guitarlounge – March 2011

elysia released a plugin version of their renowned alpha compressor on the 1st of December last year. The ad says “The ultimate mastering tool”, let’s put this piece of software on the bench press and see if it lives up to those words!

The alpha plugin supports the whole range of platforms, AU, VST, TDM, RTAS and VENUE. Hat off to elysia for that!

While being mainly aimed at mastering and final mix duties the alpha plugin comes in two versions, one mastering version with a GUI that looks more or less exactly like the hardware unit and one stripped down version that better fits the bill for single track mixing tasks. The mastering version is only available on stereo tracks, while the mix version can be used on both mono and stereo tracks.

The mix version
The Mix version of the alpha compressor does at first look very similar to elysia’s earlier release, the mpressor plugin. But looking a little closer you’ll see that there are some differences to the controls.

Looking left to right from the top we’ll find:
- Thresh
- Switchable feed forward mode
- Attack (with Auto Fast switch)
- Release (with Auto Fast switch)
- Ratio
- SC Gain (Sidechain gain)
- SC Freq (Sidechain frequency)
- Warm
- Mix
- Gain (Make-up gain)

As you notice there are quite some differences compared to the mpressor which lacks side-chain controls, switchable feed forward, auto fast release, warm and the mix feature. But instead implies Anti Log release control, negative ratios, the niveau filter EQ and gain reduction limit. Just by comparing the controls you’ll notice that the mpressor is a more of a playful compressor for the creative mind while the Alpha perhaps is more of a work-horse.

The master version
As noted above this is the version that reassembles the hardware unit, with separate controls for left and right channel and more features than the mix version. Including among other things an M/S mode, which can come in real handy at times when applying compression in the mastering phase.

Looking left to right from the top (on one side of the unit) we’ll find:
- Thresh
- Switchable feed forward mode
- Attack (with Auto Fast switch)
- Release (with Auto Fast switch)
- Ratio
- EQ Gain
- EQ Freq
- SC Gain (Sidechain gain)
- SC Freq (Sidechain frequency)
- Mix
- Gain (Make-up gain)
- Warm
- Soft Clip

Digging deeper into the alpha’s functions
It’s fairly easy to use the alpha compressor, the controls are marked and placed in an convenient way which reassembles the hardware unit, so if you are used to working with outboards you get kind of the same workflow and feel when using the alpha plugin.

For regular “simple” compression using threshold, ratio, attack, release and make-up the alpha works brilliantly and it isn’t hard to get a nice sound out of it. When using the mix version you only have one set of controls so there’s no trouble matching left and right channels (when used on a stereo track). If you use the mastering version of the plugin you get separate controls for left and right (mid/side) but still have the choice of using the link button that links the channels controls together, if you wish to get the same settings on both channels without setting both channels.

The feed forward/feedback switch changes the behavior and characteristics of the compression, meaning you get more or less two different compressors in one unit. The sound of feed forward compression is often described as tighter and punchier, while feedback compressor generally speaking might be more program dependent. But it’s dangerous to try to describe audio with words, so check out the samples below instead. I’ve included both feed forward and feedback examples of the alpha.

The Auto Fast switches for attack and release engage a semi automation that strives to provide optimal attack and release based around the values you set for them.

The EQ that you find on the mastering version implements the same design as elysia’s niveau filter which is downloadable as a free plugin from their site. The niveau filter is also found on the mpressor. The filter works kind of as a Baxandall filter, you set a frequency value and when boosting EQ curve raises everything above the selected frequency and at the same time as it lowers everything below, if you cut it does the opposite. The EQ is perfect, absolutely perfect for brightening a too dull mix or the opposite. It’s so simple yet super effective!

The alpha compressor uses an internal side chain filter for frequency selective compression within the plugin. The internal side chain function is easy and quick to use as you don’t need to do any routing or set up busses in your DAW. The side chain frequency control chooses what frequency area you want to give a stronger or weaker impact on the detection circuit of the compressor, how much weaker or stronger is set with the SC Gain control. Setting the SC Gain control to HP (High Pass) the side chain filter will act like a 6 dB high pass filter, resulting in a decrease of bass frequency compression. Setting it to LP (Low Pass) will do the opposite, less compression of high frequencies.

The mix function is nothing new in the world of compression but nonetheless really useful at times. It essentially does the same as setting up a parallel compression in a DAW, blends the compressed signal with the original uncompressed signal. So you can for example squash the material real hard and then blend that with the uncompressed one. Having it on a control in the plugin instead of needing to set up a separate bus for it in the DAW is convenient and very much appreciated!

The hardware version of the alpha compressor has switchable transformers on the output to color the sound. In the plugin version there’s a function called “Warm” instead. Engaging the “Warm” function thickens, saturates and warms up the sound coming out of the compressor slightly, nothing over the top just a nice sheen of warmth.

Looking at elysia’s own description and technical explanation of what the Warm function does they say:

“We have decided to approach this in a little different way with the software version. Here you get something similar to the Warm function known from the museq: a slew rate limiter which alters the frequency spectrum, harmonics and transient response.

Because of the mastering approach of the alpha compressor, this feature is much more of a subtle audio shaping feature than a glaring sound effect, but it’s certainly nice to add a little bit of color to a signal which might otherwise seem to be too clean.”

As with all warming and saturation effects they don’t fit everything. I’ve found the Warm function useful at times when you have a mix or track that’s too thin sound, other times even if it’s subtle it muds up the signal too much. Not for everything but it’s really useful when you need it.

A Soft Clip Limiter isn’t something that you often find on a compressor/compressor plugin. It’s a clipper/limiter that focuses on taking care of really short peaks and transients that otherwise might cause overs. The difference from a brickwall limiter lies in that the Soft Clip drives the peaks/overs into saturation much like analog tape would do, while the brickwall would forbid the peak to go anywhere over threshold. It’s great for taming transients and thus can also provide more loudness when working at the mastering stage.

Usage and sound
As described above for regular compression the alpha is straight forward and easy to use and when you want to use its more advanced functions they are right there next to the standard controls. It’s nice to have both things in one compressor and elysia has also managed to pack it into a simple user interface paired with superb precision and sound quality.

It’s a transparent compressor, which is what you should be expecting from something that is to be used for mastering tasks. It’s really solid and holds things together nicely, on everything from 1.2:1 to higher 2.2:1 style it keeps things intact without changing the sound in any other way than it should, taming peaks.

Engaging the “Warm” button give a nice saturation to the sound, without being over the top like many plugins that simulate analog equipment tend to be. When used in the right place the warm setting can really enhance the source. Listen to how it behaves on a drum bus in the clip section below, I’ve included both warm and regular feedback clips as well as warm feed forward clip.

The feed forward buttons gives you a whole new kind of compression and sound in the same plugin. Sometimes feedback tend to work better while sometimes feed forward is a fresh new way to tame peaks, A/B testing them is easily done with one click. For example check out the acoustic guitar clips below where you can really hear the difference between feedback and feed forward. The clips have been adjusted so that they have about the same amount of peak reduction while attack and release isn’t altered from clip to clip. In the acoustic guitar clip the feed forward mode is really audible and doesn’t sound that nice to me, the feedback mode works nicely though. I should note that when I adjusted attack and release for the feed forward mode setting I could get it to sound much better for the acoustic guitar as well, but in these clips below I wanted attack, release and gain reduction to be the same to give you general feel of how the two modes are different from each other.

It’s easy to overlook the power of side chain in compressor. It hit me like a train just yesterday what a powerful tool the side chain in the alpha really is, I was mastering a track where there was a lot going on at the same time. Using the side chain in the alpha compressor it allowed me to leave the bass groovy and the kick punching while still taming the peaks in the upper registers, without the side chain the compression just muddied the low end but now I was able to keep in nice and detailed while still getting the mids and highs to sit properly. I stood clear for me once again what a powerful tool the alpha compressor is, with the easy to use side chain combined with mid/side processing the possibilities are endless. You can, for example, compress the mids in the electric guitars that are panned left and right in a track while still being able to leave everything else more or less untouched, all this is in a simple stereo track. Amazing!

Sound clips
At first I had plans to record some new material and tracks for the sound clips, but reconsidered and decided to use the same clips I used in the elysia mpressor review I did back in November 2009. I normally only compare with Logic Studio plugins which are a easy to access reference to many people. But considering both the alpha compressor and the mpressor are elysia products, including it in the comparison made sense and might be useful if someone is thinking about buying one or both of these plugins.

Conclusion
From all the compressors I’ve tried so far it’s one of the most flexible units without having a overly advanced and complex user interface to deal with. It’s easy to get it good sounding on almost everything, probably because it’s so transparent yet has the option of adding a little color when need with the push of a button. It doesn’t go over the top even if you push it to its limits, though with a maximum ratio of 2.4:1 it’s not too aggressive to start with either.

It’s solid, a stable release that hasn’t crashed once on me during the two months I’ve been using it. The way it reassembles hardware with a really nicely done graphical user interface is something I appreciate and I find it much more user friendly than most DAW bundled plugins. At its given price it’s not freeware, but considering the level of sound quality and attention to detail that this plugin has I feel the price isn’t bad at all. It’s among the top when it comes to plugins in my book.

Looking for gooey dark chocolate warmth? Look elsewhere. Looking for a versatile workhorse? Look no further!