New realms of creativity

by Simon Tilbrook
Audio Media (United Kingdom) – March 2008

As someone who reviews pro audio equipment, amongst other things, it is difficult on some occasions to get enthusiastic about an upcoming piece. There are times though when my initial ideas about a unit are more than a little off. The elysia mpressor, a 2-channel compressor is an example of this. A compressor, but with a few surprises up its sleeve. The first thing that made me think something may be different was the name of the man behind the mpressor, Chief Engineer Ruben Tilgner. I have been fortunate enough to use a number of Ruben’s designs for SPL, these include the Gainstation, Mixdream, and the ever popular Transient Designer. With such a background, the mpressor had every chance of being a little different.

The elysia mpressor is a very solidly built (8 kg) discrete all class-A product with a transformerless audio path. Remove the top panel to see a beautifully designed layout within. A heated copper element is visible on each of the two channel boards that keep the transistors at a constant temperature. These transistors form the Transconductance Amplifier, the principal detection component. This design helps to massively reduce environmental distortion within the circuit. My maintenance engineer informs me this was used on early Moog designs.

Connections, Controls And Functions
The rear of the mpressor is where we see the XLR balanced connectors for each channel. There is a balanced input, output, and sidechain – identical for both sides. On the front panel of the elysia mpressor, there are two sets of identical channel controls that are separated by the circular elysia backlit legend, and channel bypass and link buttons. On each side of the legend are the gain reduction meters with all red LEDs. The layout of the channel function controls is clear and simple on the face of it, but some functions will need a little understanding to make complete sense. Threshold sits next to a sidechain trigger selection button, all very familiar, and then comes the main attack rotary control.

Next to this is the first of the interesting functions of the elysia mpressor, Auto Fast. When this button is depressed, the mpressor automatically shortens the attack time when a particularly fast and/or loud transient is detected. The channel attack time then returns immediately to the selected value. You can set up your attack time to best suit your application without having to accommodate the odd transient that takes you away from your ideal setting. Auto Fast copes with these odd events leaving your ideal setting in place, very nice indeed.

The release knob is next to another interesting function called Anti Log (Antilogarithmic). With the normal release curve, the time constant gets shorter as the signal level increases, so the short and loud peaks have a fast release time where the rest of the signal experiences a slower overall release. With the Anti Log function in place you get a reverse type of curve effect. A longer release time is experienced at the front of the signal, and the speed of this release gets faster as the signal level decreases.

The ratio has the usual type of values along with a number of negative values. The effect of these is to cause an over compression of very loud signals. Output gain is excessively reduced as the gain level increases. An EQ section is provided on the elysia mpressor in the form of a Niveau Filter. We have two rotary controls, a cut/boost +/-6 dB control, and a centre or crossover frequency selector with the range 26 to 2 kHz. This range can be altered utilising the x10 button that sits next to it. The EQ section of the mpressor can be switched in or out of signal flow with the On button. This EQ section is active after compression and immediately before the output. There is no way of changing this, perhaps a future enhancement?

The extremely well written manual explains the EQ variations very well with accompanying illustrations to show the seesaw curve variants. You use the EQ to lighten or darken the overall feel of your compressed sound. This is a somewhat unique function and requires a bit more of a description to get your head around it. Selecting a crossover frequency point, for example 3 kHz, then rotating the cut/boost control left turns down all frequencies above 3 kHz and turns up all frequencies below 3 kHz. Rotating the cut/boost to the right works in reverse. The exact shape of the EQ curve is illustrated in the manual.

GR Limit is yet another interesting function of the mpressor. When this rotary control is activated with the On button, you can set a specific level of gain reduction that will remain constant without altering any of your principal settings. It works by limiting the control voltage through the control circuit, so is not in the signal path itself at all. So you can set up the mpressor to deliver the sonic results you are looking for and then utilise the GR Limit function to maintain a constant gain reduction level without any sonic impact. The final control on the elysia mpressor is the output gain that can supply an additional 20 dB of output signal level.

Use
Taking the elysia mpressor and using it for straightforward compression tasks, the mpressor is very transparent and quiet in operation, as you would expect from a class-A device. Simple compression tasks are all quickly and simply coped with, giving as-expected results. This is not to make the mpressor sound boring or unremarkable, it does this job well, but this is not how people are really going to be using it. Looking at some of the interesting functions mentioned earlier, the Anti Log release is particularly flexible. You can create some really quite extreme pumping effects as well as introducing a slight delay to give the impression of moving away from the sound source, just like moving a mic some distance from the source in a reflective environment.

Couple this with the EQ and you can create a variety of environmental effects, or something more radical. The flexibility with the sonic qualities you can create with the elysia mpressor is limited to your time and imagination only. You will need to spend time to really appreciate what is possible with the mpressor. You can be extremely harsh with hard-edged sharp pumping drum sounds or create smooth silky vocals with the EQ… it goes on. It is impossible to convey just how much you can achieve.

Conclusion
The elysia mpressor turned out to be quite an eye opener. Once you start to appreciate the functions, and the way they can interact with one another, the possibilities of the mpressor begin to be realised. This is far more than just another compressor with a few clever bits, this is a high-end sonically stunning and highly creative device, and the more time you have with the elysia mpressor the more you will understand and the harder it will be to let it go.