A Bit Of Gear Porn

by Nigel Jopson
Resolution Magazine (United Kingdom) – March 2007

It’s a mastering oriented compressor that doesn’t look like anything else and has its own sound signature too. Nigel Jopson hits the big elysian lights as he finally gets his gnarly mitts on a bit of gear porn to review.

It has become an article of faith in some mastering circles that a round trip to analogue and back is a necessity to extract the very last drop from a song. The tools for this are the last bastion of no-compromise analogue design, the audio equivalent of hand-beaten alloy panels on custom sports cars. The alpha compressor, from German company elysia, is aimed directly at this echelon of mastering. Designed by ex-SPL crew member Ruben Tilgner, the alpha has attracted considerable attention for its dramatic appearance, with illuminated blue knobs and styling reminiscent of a software plug-in. Style can be as important as substance at the audiophile end of pro audio, just as it is in hi-fi, and – to this reviewer at least – clothing an innovative product in an innovative shell is more inspiring than the fauxvintage approach adopted by some designers.

The alpha is a dual-channel compressor with internal Mid/Side encoder-decoder, switchable sidechain EQ, integral signal path EQ, Soft Clip limiter, and additional colouration transformer. The channels run independently or linked, and innovative switching enables direct and compressed signals to be mixed – the so-called Parallel Compression technique – that normally requires a mixer and a deal of tiresome level matching. The compression circuitry uses genuinely new technology, a fully discrete Passive Current Attenuator or PCA: linear current attenuators with variable gain are not unknown in electronics, but I believe this is the first music application. elysia employs power amp output stage transistors, the 16 discrete devices at the alpha’s heart are kept at a special temperature by an ‘exclusive heating system.’ The aural result is unlike any type of analogue compressor we have become familiar with: adjusting attack and release times gave some unusual impressions. This can be a very fast compressor, but without the bite normally associated with quick attack times.

There are also some nice 100 ms+ attack times marked on the control, but I didn’t hear the ‘peak followed by crush’ sound I’d normally associate with such settings. The Feed Forward button switches the sidechain junction ahead of the gain control section for harder compression, and the Auto Fast button results in noticeably more gain reduction on transients, but seems to preserve slower developing musical passages. I’m reluctant to use the ‘L1’ word because of the negative connotations this may conjure in some minds, but my most immediate thought when first hearing the alpha was: Ultramaximizer in analogue! One of the alpha’s strong points is its solid bass management. There’s an internal sidechain section with boost/cut and centre frequency controls, the extreme left and right settings of the SC Gain convert it to low or high pass filters respectively, with the Freq control then operating as turnover rather than boost frequency. With most mastering compressors the tendency is to use a sidechain to cut bass frequencies to avoid excessive pumping, the alpha is perhaps one of the few where one might wish to experiment with a bit of LP or boost to tame a boomy track.

The EQ to the left of the SC controls is similar in operation to the ‘Tilt’ equaliser found on Quad 33/34/66 hi-fi preamps. Rather than a bell boost/cut at the selected Hz/kHz, signals above and below the chosen frequency will be boosted by up to 3 dB and synchronically cut by a maximum of 5 dB. This is rather too coarse an adjustment when mastering for CD, but using the alpha in M/S mode the EQ was useful in evaluating compression and taming muddy bass or excessively bright ambience for the Side component. In fact, because the alpha excels at gentle compression settings, I found myself using it in unlinked M/S mode most of the time. As the alpha has such a great built-in M/S matrix, insert points would be a useful added feature. Stereo analogue equalisers are always a pain to accurately adjust for mastering, which is one of the plus points of using M/S. The usefulness of the alpha to a studio where it was a trophy purchase would be considerably enhanced by outside access to the alpha’s Mid/Side signals. Most world-class mastering houses already have a matrix in their consoles, so the alpha’s encoder will never be used by them.

In fact, the alpha is so nearly an all-in-one switching and balancing mastering solution, I wonder if elysia ever considered building two companion products: a controller and a separate compressor. The Mix control, with it’s associated Direct and Compressed buttons, allows auditioning of the original, compressed or (with both buttons in) a mix of both signals. No unsettling level jumps or clicks intrude when these controls are used, I found it useful to leave the M/S configured alpha in Active mode, and then seamlessly switch in mid or side, treated/untreated/mixed signals when setting up a track. It just shows that, although analogue is a sunset technology, good designers can still come up with clever ideas.

The alpha’s Soft Clip limiter is apparently designed to protect subsequent A-D convertors from clipping, but I found its curve too gentle to have much usefulness in this regard. The manual warns ‘noticeable distortion appears if you drive this circuit too hard,’ and this is most unfortunately the case. Some mastering engineers at the cutting edge of the loudness war are actually deliberately clipping occasional peaks into their Prism or Lavry convertors, as a means of employing slightly less (or softer) analogue limiting. Perhaps a circuit that emulated this technique would be more useful for owners of less forgiving A-DCs. The Transformer button adjacent to the Clip control engages a Haufe ‘to add that certain amount of iron to your sound’. It must be a different Haufe to those installed in my vintage Telefunken pres as the effect proved rather too subtle for my jaded ears to appreciate. The alpha is full of relays and beautifully laid out PCBs. I can imagine it being the processor of choice for those in the jazz and classical fields who are now required to bow in the direction of 0 dBFS. It will be a suitable tool for mastering engineers who wish to gently caress the songs they are charged with improving, rather than those who need to carry out a full-on audio face lift.

Pros
- Exemplary build quality
- Noise-free makeup gain
- Transparent sound
- Gentle and useful increase in perceived level when used in moderation

Cons
- Tends to accentuate hi-hats and splattery HF with more extreme settings
- No insert point for M/S matrix
- Impractical Soft Clip function