Gyraf Audio G24 Compressor

The Gyraf Audio G24 Compressor is an entirely new type of stereo compressor – aimed at mix and mastering functions. This optical compressor is 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 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).

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

Tech
Most of it’s 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 analogue engines only ever interacts with your audio by directing a bit of light to an array of photo resistors 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 simultaneusly on the signal. Equals two separate stereo compressors. You can use one to grab short transients with fast timong, and the other to slowly ride gain... On top of this Gyraf Audio gives you the "Control" pot, that 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 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, off course - you may realize that FF and FB compression are subjectively perceived as two very different beasts - and the continous 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 a MS-compressor as well as a 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, in stead of loosing all "S" and getting +6dB of "M" - Sidechain Tilt 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 execptions. The industry is trying to ignore this away, and the Gyraf Audio G24 was conceived as a protest against an 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 it's 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? Bypass is as always full-relay, and Gyraf Audio G24 has a output trim function for easing comparison between direct and processed material.

Gyraf Audio G24 Compressor Features

• 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