Groove Tubes “The Glory” Transconductance Valve Compressor

In excellent condition, very clean but for a few very small marks. Complete with original box, rack braces for added support (they weigh a lot!) and includes 3 months warranty. Unit has been converted for 240v operation, but also ship with original 110V transformers for reversing back to 110V use if need be.

The Groove Tubes Glory compressor is a 3u behemoth of a unit, weighing in at over 17kg and offering a wide palette of sonic flavours, from subtle, transparent transient taming, to thick, smooth and characterful compression indicative of iconic vintage units. The Glory Comp, which employs a total of seven vacuum tubes, features conventional Threshold, Attack, Release and Ratio controls, as well as a rather more unusual ‘Glory’ knob (marked ‘Heaven’ at one extreme and ‘Earth’ at the other), which controls the amount of harmonic distortion introduced by the valve circuitry. Compression ratios from 1:1 to 10:1 are available and users can choose between logarithmic and linear release modes. A backlit VU meter can be set to display input, output or side-chain level or gain reduction. An internal side-chain EQ is provided, featuring low- and high-frequency filters. Alternatively, the Glory Comp can accept an external side-chain source. Finally, the unit can be linked to a second Glory Comp for stereo compression.

The Glory Knob

This unique control adjusts the intensity of the Glory Effect as mixed into the processed signal. Specifically, the Effect is summed with the post-compressed audio being fed to the compressor’s driver and power output stage.the Glory Control, and what does it do? The Glory Effect essentially consists of special circuitry that samples the program input signal, from which low-order even harmonics are generated, over a limited band of frequencies, and intentionally added back to the compressed signal in amounts deemed by the user to be appropriate for the sonic events at hand. The harmonic bandwidth is confined to operate on signal fundamental frequencies from 40 to 700 Hz.

Variable transconductance tube gain stage.

The Groove Tubes Glory Compressor is, first and foremost, an all-tube compressor. Inside, the program audio is multiplied by nothing but tubes, as the Program signal propagates from the main input jacks to the main output plugs and jacks.Each stage, and there are four distinct amplifier stages, consists of pairs of carefully balanced and self-balancing push-pull class-A vacuum-tube circuits. This includes the electronically controlled vacuum-tube-based variable gain stage. Very much the exception in what are today generically referred to as “all-tube” compressors, the Glory Comp makes use of the spectacularly linear and specially selected remote-cut-off 5749 pentode operating in the triode mode. These variable-transconductance tubes handle the delicate task of modulating the program signal level. The most important of the desirable characteristics that this tube provides are a superbly wide dynamic control range approaching 20 dB (near a 10-to-1voltage reduction), coupled with freedom from undesirable artefacts. Twenty dB of clean gain reduction represents the greatest practical limit for a factory-built audio production compressor based on a single balanced stage of variable-gain tube circuitry.The sonic bonus of using this tube type is a delightfully smooth and suave gain-change characteristic as the variable gain stage sweeps through its control range. Being more linear and more “invisible” than alternative 6386-based designs, users will find that only the most extreme control settings produce audible compression phenomenon.

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