Gyraf G24

SKU: G24

Passive/ Aggressive Compressor


About this item



The Gyraf G24 is an entirely new type of stereo compressor – aimed at mix and mastering functions. Like it’s sister and predecessor, the G23 EQ, it’s for those situations where you have a mix that is already nearly-perfect balanced, but you want to control some part of its dynamic without messing up the overall definition.

The G24 is as standard available as 230V or 115V mains voltages – Please specify when ordering.

The Gyraf Audio G24 Compressor is an optical compressor based on re-thinking large parts of the traditional compression concept. First of all: It’s passive. Really. In passive mode, your audio will only pass through one resistor, one audio transformer, one opto cell, and the output level potentiometer. It kept this simple in order to mess minimally with your material. This, of course, comes at a cost: The input/output impedance requirements for interfacing to the Gyraf Audio G24 are quite strict, but no worries: At the “Bypass” switch, Gyraf Audio added one further step: “Active”, which switches in a very-high-grade unity-gain buffer that will drive even the most difficult load. Solid-state, yes – and invisible (to your ears anyway).

Gentleness and subtlety were again Gyraf Audio’s main design targets here: The Gyraf Audio G24 Compressor is based on a carefully designed fully passive signal path, consisting of one metal film resistor, one audio transformer and one photoresistor per channel.

Most of its intricate control system was conceived from scratch, following a stringent “what-if” paradigm of research, trial, and error. The elaborate sidechain and controls need active electronics (and thus a power supply, contrary to G21) – but all these analog engines only ever interact with your audio by directing a bit of light to an array of photoresistors dragging that channel towards one or the other phase of the opposite channel signal. Nothing else. – Dual sidechain. No, not just a dual-mono option, but two separate stereo-compressor sidechains acting simultaneously on the signal. Equals two separate stereo compressors. You can use one to grab short transients with fast timing, and the other to slowly ride gain… On top of this Gyraf Audio gives you the “Control” pot, which morphs seamlessly between the two compressors – Gradually variable all the way from L/R to M/S. Yes, although the Gyraf Audio G24 can be thought of as a couple of stereo compressors, it is, in reality, two M/S compressors that are fully variable all the way from M-only (Mid component) to S-only (Side component) – the beauty being that when the “Elliptic” control is centered, (M-compression = S-compression), it acts (and is) the same as a stereo compressor. or rather: Two stereo compressors. – Compression Fully variable from FeedForward to FeedBack. Now wait, two individual compressors, you say: But how do you decide which of those comes first? Kinda important factor in compression, is it not? Aah yes. Gyraf Audio included a “Feed” control for your convenience, allowing you to dial in a setting from feed-forward to feedback INCLUDING everything in-between. You are not limited to having just one of them first (or last) – you can set both of them as you want, e.g. having both first (!). Uh – and you can set them in-between also, of course – you may realize that FF and FB compression are subjectively perceived as two very different beasts – and the continuous fade between their ways makes a lot of sense. – Mono-compatible Sidechain signal summing for M/S collapsing to make sense. When initially trying to think up this compressor, the main design obstacle was about keeping the sidechain (relatively) simple. As Gyraf Audio really wants both L, R, M, and S to be able to contribute to the derived control voltages (because it’s an MS-compressor as well as an LR), they could not simply add input/output signals to derive a singular signal for the sidechain, as this would completely cancel out the “Side” part of the signal, leaving us with only “Mid” component. One – in reality almost impossible – option would be to build four tracking sidechains and then sum them before Ratio control. What they did is something old and new: They re-purposed an ancient signal processor that was designed to maintain mono compatibility for stereo signals e.g. when transmitted over AM – this processor shifts signal phase +90 and -90 degrees in the two (LR), which ensures that when adding the two channels after processing, you get +3dB Side component and +3dB Mid, instead of loosing all “S” and getting +6dB of “M” – Sidechain ambler emphasis. One meter – some metering compromises.

The Catch
As you may or may not know, optical compressors can no longer be sold in the EU or California. No exceptions. The industry is trying to ignore this away, and the Gyraf Audio G24 was conceived as a protest against environmental legislation that allows massive amounts of Cadmium for batteries, yet bans an entire division of audio processing in order to save the environment from the very small amounts of Cd in these OptoCouplers. All very technical and sad, don’t get me started… The “Aggressive” part of the unit’s name comes not from its way of behaving, but from the aim of stirring up the soup to get some sort of focus on the unbearable situation for real pro audio because of these rules… That is; You want one, Gyraf Audio will need you to sign an agreement that they own the heart, and that at some time (if ever), when they have found a suitable replacement material and shipped you a module containing a new and legal part, that you will open the unit, plug the new one in, and send the old one home to them. They have arranged a disposal ritual as a small yellow-orange dot on a piece of pottery from a local artist – this is one of the legal uses of cadmium. So prepare for some paperwork if you’re in the EU or California like 95% of their customers. Gyraf Audio G24 is M/S, two sets of controls – and passive. There is an option to buffer output to ensure drive capability for difficult loads if such are encountered. G21 anyone? The bypass is as always full-relay, and Gyraf Audio G24 has an output trim function for easing a comparison between direct and processed material.

Gyraf Audio G24 Compressor Features
The completely passive signal path
Dual sidechain, which effectively means there are two available compressors that act upon the source
Continuously variable L/R to M/S
Continuously variable compression characteristic between FeedForward and FeedBack

Gyraf Audio G24 Compressor Specifications
Type: Unique Passive Stereo Compressor
Sidechain: Dual Stereo Sidechain
Modes: Continuously Variable between L/R to M/S and Feedforward to Feedback Modes
Valve / Solid State: Valve
Channel Count: Dual Channel
Chassis: Rackmount
Compression Type: Optical
Mains Voltages: 230V or 115V

Gyraf Audio G24 Compressor Includes
Gyraf Audio G24 Compressor
Power Cord
User Manual
2 Year Warranty


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