Plugin adaption of a successful mastering compressor

by Andreas Eberhardt
Buenasideas (Germany) – February 2011

Since their start as a company in 2005 the developers from elysia have been following a certain philosophy. Instead of accepting the status quo as the final state of the industry, they like to think laterally in order to create products which meet today's production requirements.

We have just taken a closer look (and listen, of course) at their recently released alpha compressor plugin, an emulation of their similar hardware processor into the VST, AU, RTAS, TDM and Venue formats. elysia has contracted the specialists from Brainworx who have been adding some fresh spirit (e.g. with their bx_XL limiter) to the software market for this job.

Looking at the many aspects to be considered when translating a hardware machine into software, it becomes obvious that this cannot really be a child's play. On the contrary, it is a tedious process to emulate the more or less exact behavior of a hardware unit, which is something completely different than using VST-Lego like construction kits like SynthEdit or Synthmaker. And the fact that the alpha compressor hardware is a fully discrete design does not make the challenge easier as well.

Audio hardware products are much more sexy than their digital emulations – there is lights, even smell, you can touch things and play with all the controllers. Moving virtual potentiometers and faders has never been the same kind of joy. Only after VST 3 has been released, there are such things like mouse wheel controlled knobs, and the alpha compressor by elysia also offers this.

And it is really a nice advantage in terms of haptics – at least it feels a little bit like really moving the controls. Of course this can be further improved by using an external hardware controller like the Ci2+ or even better the Steinberg CC121, but the mouse wheel control is certainly a step into the right direction.

A specialty of the alpha compressor, both in hardware and software, is the consequent implementation of its M/S mode. With it, you can split the stereo signal into a mid (M) and a side (S) signal which can then be processed independently from each other.

M/S technology is not really new. For example, if you're getting into your car and listening to good old FM radio instead of CD or MP3, you will sometimes notice that the side or stereo reception will drop when the reception is not good enough, leaving just the mid or mono channel to be heard. When the reception becomes better again, the stereo image will also open up again. Broadcasting stations have been using this technology successfully for decades.

When used in music production, the split into a mid and a side channel can also be very useful. One should give it a try in order to really understand what is happening then, but there is also a detailed description available on the elysia website. On top of this, we will show the potentials of this technique at the end of the review in a little video.

The alpha compressor plugin needs an iLok for licensing. I have to say that at the beginning I did not like the iLok system at all, as in my mind this shifted the problems of the software companies on towards the honest and paying customers. But also I have to admit that in the meantime I have pretty much adapted to this system painlessly. Once the license is on the USB dongle, I don't have to care about searching serial numbers and challenge/response codes when I have to reinstall my system. Looking at things from this angle, both the iLok and the eLincenser by Steinberg are very convenient to use.

Let's get it on!
The alpha compressor produces a damn good sound without adding any vintage coloration, and the user interface looks also very nice indeed. It seems so real that it sometimes makes you want to grab those knobs on your screen.

Next to the classic compressor parameters like Threshold, Attack, Release and Ratio we find a Niveau Filter which is specialized in changing the character of your audio material by the use of only two controllers. By the way, elysia offers this filter as a free plugin on their website (and I have to say it is working like a charm). The alpha compressor also offers frequency-selective compression, which is nice as you do not need additional routings for the sidechain.

But this is not the end of special features at all. Furthermore, we find a parallel compression stage which can blend between the dry and the compressed audio signals with a mix controller.

The signal matrix is also very efficient and implemented in an ergonomic way. With it, you can listen to only the compressed or only the direct signals solo. Only when both direct and processed switched are active the mix controller is active. This works both in stereo and in M/S mode, making it possible to compare or bypass single channels independently from each other.

Like mentioned before, the alpha compressor plugin has not too much in common with a vintage compressor which would include some kind of analog coloration by nature. However, coloration is something very useful from time to time... For this reason, the hardware version of the alpha compressors features additional output transformers which can be switched into the mix stages as an additional means of sound shaping.

The software emulation walks a slightly different road in this regard. The original 'Transformer' circuit of the alpha compressor has been replaced by a Slewrate Limiter which influences the frequency range, harmonics and impulse timing. This creates a subtle but pleasant coloration of the audio signals.

A the end of the signal chain we find another very useful assistant: the Soft Clip Limiter. This stage has been implemented in order to securely handle short transients. However, this is not based on a classic brick-wall limiter design which would not allow anything to pass a certain threshold. The Soft Clip Limiter raises the available headroom and loudness, but it does not behave as choppy as a standard limiter would.

Double act!
The alpha compressor plugin appears in two variants – the master compressor which we have been looking at so far, and the additional mix variant to be used on single channels. The mix interface does not include the M/S and signal matrix options, but it is a very effective compressor plugin for processing single instrument tracks and the like. Here we also come across a very important advantage of software, as you can freely multiply the number of compressors used at no upcharge (and you also cannot save your settings with the hardware as well).

The following gives you a short sum-up of the technical specialties of the alpha compressor:
- Integrated M/S Matrix: Mid/Side and stereo processing modes
- Auto Fast: Perfect attack and release in any situation
- Feed Forward & Feedback: Two selectable compressor characteristics
- Sidechain Filter
: Frequency selective compression
- Parallel Compression: Mixing direct and compressed signals
- Soft Clip Limiter: More headroom, more loudness
- Audio Filter: Tweaking the sonic structure easily
- Warm Mode: Instant signal coloration

Result
I am tossing pretty much all of my other compressor plugins into the trash! With the alpha compressor, elysia has created a plugin that does such a great job at a pretty low CPU load that it is pretty hard to believe. No matter if used for mastering or single tracks: the alpha compressor satisfies. It is astounding that a 'program' can sound this good.

If you want to form our own opinion on the potentials of the alpha compressor plugin, you can do so by downloading the free trial version from the elysia website. I really have to say: I am always glad when testing a new plugin is fun, and the alpha compressor even made me happy. So even if I wanted, I could not stop myself from decorating this plugin with the buenasideas.de editor's recommendation!