Mercury 666 Studio Limiting Amplifier

This high‑end design began life as a resurrection of the rare‑as‑hen’s‑teeth Fairchild 666. But it soon became its own thing...

After many years spent repairing and racking vintage equipment, David Marquette wanted to develop his own designs using the best parts of the technology he’d worked on over the years. To that end, back in 1999, he founded California‑based Mercury Recording Equipment. Mercury are celebrating their 25th anniversary this year, and have released many products over the years. From their first three designs, the Fairchild 660‑inspired Mercury 66 Limiter and the EQ‑H1 and EQ‑P1 equalisers, to their highly regarded Mercury M72s and M76m mic preamps based on the Telefunken/Siemens V72s and V76m, all Mercury’s products are hand‑built by a very small team — they’re the very definition of a high‑end boutique pro audio company . While this means they don’t come cheap, it’s fair to say that they’re all much less expensive than the rare vintage designs that inspired them or that they’re intended to complement.

Overview

The latest addition to Mercury’s line‑up is the 666 Limiting Amplifier. Inspired by the Fairchild 666, this is a mono, hybrid (solid‑state and valve) compressor but it isn’t an outright clone. The original Fairchild 666 held plenty of sonic appeal but, putting it politely, a very limited set of user controls, with many adjustments requiring a screwdriver. Mercury felt this would make a straight reproduction a tough sell in today’s recording market so, early in the planning stage, they took the decision to create a new device that, while still ‘leaning on’ the sonic heritage of the original, would feature plenty of enhancements to make it more relevant to modern studios.

The solid‑state part of the equation lies in the dynamics processing, in the form of the custom‑designed Mercury SSGRE gain‑reduction element. Then comes the valve make‑up gain stage, featuring a 12BH7 valve and a custom Cinemag output transformer. Finally, among the new features is a Baxandall shelving EQ, an unusual feature to include on a compressor and one that really caught my eye. Apparently, the designers felt that the simple tone controls of the classic Baxandall filter would be a worthy addition to a compressor that users would probably already be looking to for it’s tone‑shaping qualities as much as for controlling dynamics. It’s a good call — I’ve always been a fan of the wide, forgiving curves of this style of EQ, whose controls to add or cut bass and treble may be simple but can be very effective.

Controls &...