The transistor amplifier offers a maximum gain of just 3.5dB, which might not sound much to recording and mix engineers but I will not criticise this because it is more than enough for most mastering applications — and it's in keeping with the overall concept of the unit. Nonetheless, potential users must be aware of this — it's certainly not a typical run-of-the-mill optical compressor! The other thing I should alert potential users to is the gain staging of the unit: the G24 was originally designed to drive, and was tested with, analogue tape recorders working at slightly lower levels than modern DAWs and converters (which often operate at +24dBu for 0dBFS). The G24 feels more comfortable with levels around +15dBu, so levels should be set carefully for optimum results.
The rear panel of Gyraf's G24 Passive-Aggressive Cadmium Compressor features only stereo I/O connections on XLR sockets, and a mains inlet.The G24 hardware is every bit as sturdy as one would expect from an experienced boutique manufacturer such as Gyraf. All knobs and controls feel solid, the typically Gyraf steampunk front panel looks beautiful, and the rear panel offers nothing more than a power inlet and the left and right signal inputs and outputs on XLR connectors. Despite feeling adequately solid, the whole unit is surprisingly lightweight, hinting at the simple audio path layout under the hood.
Speaking of which, all components, including the power supply, fit on a single PCB which occupies perhaps a third of the case's interior. Only the opto couplers are placed inside a plastic enclosure in the centre of the unit. Despite the simple audio path, the PCB holds more components than I expected; the G24's approach to side-chain control is very sophisticated, and it shows here! The passive/active/bypass switch is buffered with relays and quality components are employed throughout, including analogue ICs by Analog Devices for the active buffer amplifier. This is a concept found in several other high-end units, including the Vertigo Sound VSC‑2, where the sound (or the lack thereof; the transparency) comes from the previous stages made from discrete components, and a simple amplifier based on high-bandwidth ICs forms the 'sonically invisible' output stage. Apart from the Lundahl transformers and the VU meter, there are not many particularly expensive parts inside the G24. What you pay for is the unique concept, the design effort, the flexible, carefully conceived and tuned set of controls, the neat and tidy construction, and, of course, the sound!
The entire circuitry, most of which is reserved for the side-chains, fits on a fairly small PCB. Note the container for the opto coupler in the foreground and the pair of Lundahl LL5402 audio transformers on the left-hand side.
In Use
I must admit I was slightly intimidated when first approaching the G24. An unusual concept, a very complex set of controls, a manual replete with several precautions regarding impedance and level matching — all these factors form a recipe for a long learning period. But the beauty of analogue gear is that you can get hands-on very quickly, and although the 2U front panel is brimming with no fewer than 17 controls, there's no law requiring one to use them all at once.
In fact, to ease your way into understanding the capabilities of the Gyraf compressor, it's as well to start simple: put the unit in active mode, for which it's less critical where and how you place it in the chain, set the A/B control fully anticlockwise (so only the A side-chain is active), and the Elliptic control to quasi-L/R mode, and start tweaking. Only when you've acquired a better understanding of the character and behaviour of the G24 do you then begin to employ the second side-chain and start playing with the M-S options. In other words, the G24 can act as a fairly straightforward dynamics processor and it's worth getting to know it as such. But then there is a whole world waiting to be explored beyond the limits of a conventional compressor...
I've used the G24 in a range of different scenarios before putting down my thoughts for this review. Among these, I've set it up as a mix-bus compressor, driving a Manultec Orca Bay EQ, with both units employed in the master insert of my Speck Electronics Lilo console. I also put it in a simple D-A/A-D loop via my Lavry Blue converters. While, as I expected, the sound picture remained entirely consistent using the active output stage, in passive mode both the output level and the frequency response varied considerably, and none of the gear mentioned is potentially tricky vintage valve equipment. This goes to show that careful experimenting is required when planning to use the G24 in passive mode, both in terms of the audio chain and the gain staging. If you found a decent spot for the G24, chances are the frequency response may still vary slightly between active and passive modes. You may find this makes it more difficult to compare options, but you can also you this to your advantage — one more colour on your palette!
One thing that may come as a surprise is that the G24 still manages to offer some make-up gain when running in passive mode. How is this possible? Did Gyraf finally invent the perpetuum mobile? The truth may be a little less glamorous, but it doesn't take away anything from the ingenuity on display here. The reason is that the Lundahl LL5402 transformers are wired in a 1:2 step-up manner, and this provides some 4-5 dB of make-up gain even in passive mode. What also quickly becomes apparent is that the G24 can both yield the very subtle results so often required in audio mastering, but it can also seriously twist and mess up the sound. A little turn on the controls can often go a very long way, and there are vast options to explore, so it certainly helps to have a solid idea of where to go sonically before you even start touching the controls. (This is one of these analogue processors where one might wish for an 'undo history'!)
It should also be noted that the profusion of controls is definitely not meant as a 'show of force': each one has a profound effect on the outcome, and you will always find and have a preference. Admittedly some of this can only fully be understood and appreciated when you actually turn the knobs yourself. In combination with the soft compression ratios often required for mix-bus compression, it was really difficult to produce a number of audio examples that are both adequate to the source and show the full capabilities of the G24. The compression action itself is open and transparent, it can deliver both fast and punchy or very gentle and clean results, not unlike those offered by other quality optical compressors such as the Pendulum OCL-2. The special beauty of the G24 lies in the more unique features (and combinations of them) such as the blending between feedback and feedforward compression. In practice, this control allows a three-dimensional handle on the sound that I haven't experienced with any other processor, and its results may be worth the price of admission alone! The range goes from wide and relaxed results that are almost too loose in feedback operation, to a very focused, tangible and solid sound picture in feedforward mode. It's worth me highlighting that, given the option, I normally prefer feedback compression for almost any application. The G24 is the first dynamic processor I came across that actually makes me appreciate feedforward compression. In practice, I often ended up somewhere in the middle, around the 12-noon setting: it offered the best of both worlds with just the right touch of relaxation and focus. But, again: to fully understand the rare beauty of this control, you really have to turn it yourself!
The same goes for the M-S feature and the side-chain filter, and the multiplication of options courtesy of the dual side-chain architecture. In short, the Gyraf G24 offers practically endless options and is capable of some previously unheard-of results, and the path to harvesting those results can be a very rewarding (albeit long) one. While its signal path is short and sweet, the G24 is not simply a 'wire with gain'. It works on the very transparent side of things, but it does offer its own subtle sonic imprint on the program material, one that is greatly defined by the characteristics of the Lundahl transformers. This results in a slight roll-off in the lowest bass register and a very gentle push in the mid-range in active mode. While this can provide some much-wanted clarity and focus in some more acoustic genres, it could sometimes seem a little counter-intuitive for modern bass-heavy electronic styles — so this effect is worth mentioning, but it's subtle, and if it's not what you desire, it's nothing that can't be corrected for with a very slight bass lift with an EQ.
Conclusion
To sum up, the Gyraf 24 boasts everything we can expect of a boutique mastering compressor and then some! Stripped of its unique features, it would still be a very high-quality audio processor, but Jakob Erland's outside-the-box thinking has supercharged this unit with concepts, features and sonic results that were previously unheard. Given the complexity of the design and controls, the G24 is not for the faint-hearted. It might not have the mass appeal of, say, an 1176 or LA-2A, and neither, as with many mastering devices, does all of this come cheap. But it is wonderful and it is innovative — it's a truly ground–breaking design that tickles the senses like a three-star menu while offering all the joy and heart-warming satisfaction of a simple shepherd's pie. How refreshing it is to find such an envelope-pushing gem in today's sea of warmed-up vintage circuits, and how gratifying to find that it doesn't simply come as an engineering exercise, but as an audio processor with a sonic palette as beautiful and serious as one
could ever wish for!
Alternatives
While plenty of 'mastering-grade' optical compressors are available, the feature set of the Gyraf is truly unique. That said, some current and out-of-production designs do share certain similarities with the G24. The Neve 33609 also offers two 'stacked', though less flexible, side-chains. The GML 2030 boasts unique and detailed side-chain control. The Amtec Phanzen offers an entirely passive signal path too, but as a diode-bridge limiter it's intended to sound very coloured, and it is phantom powered (designed to be used between the microphone and preamp) so is not a mastering compressor at all.
Audio Examples
I've prepared a number of audio examples (details below) illustrating some different aspects of the G24. You can download a ZIP file of hi–res WAV audio examples in the righthand Media sidebar or use the link below.
Download | 161 MB
ELECTRONIC
These examples use different settings of the G24 on a house track. The compression itself offers punch and glue, while the sound comes forward at the slight expense of some heft in the lowest octave. I would probably lift the bass around 1dB around 50Hz to compensate for this.
01. Original.
02. 50/50 Feed, L/R, Active.
03. 50/50 Feed, L/R, Passive.
04. Feedforward, L/R, Active.
05. Feedback, L/R, Active.
06. 50/50 Feed, More M Compression, Pink Emphasis, Active.
BALLAD
Gentle and 'creamy' results with the G24 on an R&B ballad.
01. Original.
02. 50/50 Feed, L/R, Active.
03. 50/50 Feed, L/R, Passive.
04. Feedforward, L/R, Active.
05. Feedback, L/R, Active.
06. 50/50 Feed, More M Compression, Pink Emphasis, Active.
Optical Illusions
One of the main issues that fuelled Jakob Erland's development of this 'Passive-Aggressive' compressor — and gave the device this name — was the European Union's implementation of the RoHS (Restriction of Hazardous Substances) directive, a framework controlling the use of hazardous materials in the manufacturing of electronic and electrical equipment. The RoHS directive has noble aims, and it is, on the whole, deserving of support. But unfortunately, as with many regulations, its implementation has been imperfect and it has significant implications for audio hardware manufacturers.
This isn't the place to describe the directive in detail, but it's important to know that one of the substances controlled by RoHS is cadmium. And since cadmium is used in the photoresistors employed in the opto couplers, the directive has effectively banned opto couplers from being sold in audio processors (or other devices) in the EU. RoHS doesn't entirely ban the use of cadmium — it depends on the way the substance occurs — but in a photoresistor it can be separated mechanically (ie. scraped) from the other components, and this is not allowed, regardless of the tiny amount of cadmium required in such a component. One of the G24's aluminium handles on its front plate contains — perfectly legally — more cadmium (as impurity) than its opto couplers. Happily, Jakob Erland believes he has come up with a way to use the opto coupler in the G24 without contravening the new rules!
Pros
- Utterly unique.
- Extremely flexible controls.
- Massively versatile side-chains.
- Great-sounding results.
- Quality hardware.
Cons
- Passive mode requires careful interfacing with other devices.
Summary
Aimed predominantly at mastering applications, this is one of the most unusual dynamic processors I've encountered — in fact, the G24 offers a new way of thinking about, working with and applying audio compression. It's not without quirks and the price positions it amongst the higher-end competition, but it's a truly outstanding processor that's capable of great-sounding results — and in my view it is worth every penny.
information
$3883 (as converted from Euros list price when going to press).
Gyraf +45 5129 2769.