Mercury 666 Studio Limiting Amplifier

Hybrid studio limiting amplifier modeled after the ultra-rare Fairchild 666 featuring a solid-state gain reduction element, 12AX7 and 12BH7 tubes, and a custom output transformer



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The Mercury 666 is a recreation of the mysterious classic, the Fairchild 666. Like the Fairchild, the Mercury 666 is a hybrid solid-state and valve (tube) Studio Limiting Amplifier (compressor). The new, ’Mercury SSGRE’ (solid-state gain reduction element) is a gain attenuator that does not provide any gain to the signal. All of the gain makeup after the ‘SSGRE’ in the Mercury 666 is provided by a separate two tube, single ended, gain make up amplifier. Using a 12AX7, 12BH7 valves (tubes) and a custom output transformer.

The Fairchild 666 had a feature set that did not allow it to be flexible enough for modern recording with compression control, compression release, gain control, input level and “auto-ten” functions for threshold and for release (note: auto-ten = Auto attenuation). Most features did not even have a knob you had to use a screwdriver for the control. So we designed the Mercury 666 to be more of a modern, hybrid 660 with any and all features you might need at your finger tips.

The Meter Controls include the Zero Control that allows you too easily “zero the meter” with a small knob (when Meter Select is in down position). Much easier than using a screwdriver like on the “vintage units”. To the right, of the Zero Control, is the Meter Select Switch in the down position you are in gain reduction mode and in the up position you can monitor the output level of the Mercury 666 Limiting Amplifier.

To the right of the meter, on the top row, is the Threshold Control that allows you to set the point that gain reduction begins. The Threshold Control has 11 position pot for easy recallability. To the right of Threshold is the Attack Release Switch (or Time Constant). This a rotary switch with 11 attack/release settings. The first 6 settings are the same as a Vintage Fairchild 660 (see below). The next 5 settings (7-11) make the Mercury 666 much more flexible than the original 666 or any similar tube limiter by expanding the range of control with very useful settings. The Output Gain Control allows you control of amount of ‘make up gain’ after the signal has been “compressed” by using the Threshold Control.

The 666 features a Baxandall EQ with a Low (bass) and High (treble) bands. Baxandall equalizers are shelving EQs with an extremely wide Q curve and a gentle slope. The broad curve can adjust a larger portion of the frequency spectrum, but the gentle slope gives a more natural sound and very minimal phase distortion. The Low control is ±10 dB @20 Hz and ±5 dB @350 Hz simultaneously. The Treble control is ±6 dB @20 kHz and ±3 dB @2K5 simultaneously. Both High and Low Controls have 11 position pot for easy recallability. The EQ allows you to have extensive control over the tone of the limiter and literally hands you the flexibility to get the sound that you’re looking for instantaneously.

On the back of the Mercury 666’s gray hamertone chassis there is an AC socket on left side to take 115V (.400mA) or 230V AC (.200mA) and a Fuse Holder. On the right side there is a input plate with a gold pin XLRs for (Line) Input and Output. Under the Line Input and Output, are the Insert Send and Return connections using a Combination Jack, ie Female XLR and TRS 1/4” jack, for the Insert Return and another gold pin XLR for Insert Send. Below that is the Stereo Link Connector, which is a 1/4“ (TS) jack to connect from one Mercury 666 to a second M666. Activating the front panel Link switch (on both units) enables the Mercury 666 Limiting Amplifiers to be used as a stereo pair… making a stellar, flexible, & very musical two-bus compressor / limiter.

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