Mercury Recording M666

The Mercury 666 is a new version of a mysterious classic… the Fairchild 666 which is not as well known as the Fairchild 660 (like our Mercury 66) or the Fairchild 670. We always try to be faithful to the original we are paying homage too, but, in this case so many changes needed to be made to make it more useful for modern recording we felt it was a great opportunity to make it the ultimate benchmark in modern tube compressors / limiters. We made the Mercury 666 quieter, more flexible and added an expanded feature set that is second to none let alone better than the original . Our goal was not to make it ‘as good’, but beyond better, and we feel we succeeded in doing that.

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 single ended, tube, gain make up amplifier. Using a 12BH7 valve (tube) and a custom U.S. made (Cinemag) 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.

Mercury 666 features (L to R): Link Switch with LED. The Mercury 666 is Mono, but linkable for Stereo using the (Stereo) ‘Link Switch.’ In the down position that unit is not linked to the other. In the up position it is now engaged to be linked to a second Mercury 666 and the LED will then be illuminated. You would have to engage the ‘Link Switch’ on the other unit as well to make them be “stereo linked”. You can link two (2) Mercury 666 Limiters together via a standard, high quality, 1/4” (TS) cable.

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 an 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.

Attack Release Settings

Position 01 – Fast Attack w/ Fast Release, In Seconds, Attack [ 0.4 ], Release [ 0.1 ]
Position 02 – Medium Attack w/ Medium Release, In Seconds, Attack [ 0.8 ], Release [ 0.6 ]
Position 03 – Medium Attack w/ Medium Release, In Seconds, Attack [ 0.8 ], Release [ .90 ]
Position 04 – Slow Attack w/ Slow Release, In Seconds, Attack [ 1.6 ], Release [ 1.75 ]
Position 05 – Medium Attack w/ Med. Release, In Seconds, Attack [ 0.8 ], Rel. 1 [ .90 ], Rel. 2 [ .75 ]
Position 06 – Fast Attack w/ Fast Rel, In Seconds, Attack [ 0.4 ] Rel 1 [ .45 ], Rel 2 [ .75 ], Rel 3 [ 2.0 ] )
Position 07 – Fast Attack w/ Medium Release, In Seconds, Attack [ 0.4 ] Release [ 0.45 ]
Position 08 – Fast Attack with Slow Release, In Seconds, Attack [ 0.4 ] Release [ 2.0 ]
Position 08 – Fast Attack with Slow Release, In Seconds, Attack [ 0.4 ] Release [ 2.0 ]
Position 09 – (LA3A) Med. Attack w/ Med. Double Slope Rel, In Seconds, Attack [1.6], Rel 1 [.06], Rel 2 [3.13] Position 10 – (GATES Sta Level) single slope mode, In Seconds, Attack [ .87 ], Release [ 7.26 ]
Position 11 – (GATES Sta Level) double slope mode, In Seconds, Att. [ .27 ], Rel. 1 [ 2.30 ], Rel. 2 [ 10.7 ]

Threshold: inf to -20 dB Output: -inf to 30 dB

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 DC Adjust allows you to have even more control and flexibility. It works similarly to DC Threshold on a 660 or DC Adjust on our Mercury 66. This controls the voltage that increases or decreases the starting point when/where the “compression” starts at the ‘Mercury SSGRE’ (solid-state gain reduction element). Allowing more or less or a quicker or slower reaction to the input signal, similar to a Knee Control, allowing a variable swing between Less/Soft Knee/Less Voltage and More/Hard Knee/More Voltage. This control has an 11 position pot for easy recallability!

On the bottom row, to the right of the meter, is the Side Chain Filter Switch this is a three position rotary switch. With an off position and 90 and 150 Hz filter settings for the the side chain. This allows you to filter out low end frequencies below 90Hz or 150Hz before going to limiting amplifier but not affecting or “EQing” the signal.

The Insert On/Off Switch allows you to leave the insert connections (on rear of M666 chassis) connected, to your patch bay for example, and control if the insert is being used in the sidechain or not. When the Insert On/Off Switch is engaged (in up position) and the associated LED is illuminated, the connection from the side chain insert return is being sent to the side chain. When the Insert On/Off Switch is not engaged (in down position & the LED is off) the side chain no longer receives signal from the Balanced Insert connections therefore bypassing the inserted signal.

EQ. This is a two band, *Baxandall EQ with a Low (Bass) and High (Treble). The EQ has Low (Bass) Control is +/- 10dB @ 20Hz and +/- 5dB @ 350Hz simultaneously. The Treble (High) Control is +/- 6dB @ 20K and +/- 3dB @ 2K5 simultaneously. Both HIgh and Low Controls have 11 position pot for easy recallability. The EQ section is a great feature on the Mercury 666 Limiting Amplifier. It allows you to have so much control over the tone of the limiter and literally hands you the flexibility to get the sound that you’re looking for instantaneously.

* The Baxandall equalizer is a shelving EQ 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 Bypass On/Off allows you to listen to exactly what is coming in to the device without going through any circuitry of the Mercury 666. If you engage the switch in the up position the LED will illuminate and you would now be listening to your source material directly. In the down position of the Bypass On/Off this “hard bypass” is Off. But you also have more flexibility with the Mix Control (wet/dry). This allows you to mix between the “Wet” (100%) compressed output signal of the Mercury 666 or the dry, uncompressed (0%) source with 11 position pot for easy recallability. Note: signal is going through the circuitry of the Mercury 666 unlike the (Hard) Bypass. With the combination of these two features the Bypass Control On/Off Switch and the Mix Control, or wet/dry, it allows you to hear the original source as well as a extensive range of blended source and the compressed signal, or “parallel compression.“

On the back of the Mercury 666’s gray hammer-tone 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.

Check out this great video by our friends at FUNKY JUNK. Or go to our MERCURY YOUTUBE CHANNEL for more online demos!

Mercury 666 Data Sheet