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Tube Pre-Amp Captures Key Component of the Beatles’ Sound

The Beatles’ recordings are arguably the most dissected pop songs of all time. The studios they were recorded in, the instruments used, and the signal chain from the microphones all the way to the mixing desk above EMI’s Abbey Road Studio 2, where the Beatles did the bulk of their recording, have all been analyzed and written about to the nth degree. The microphones the Beatles used for their vocals were typically Neumann U-47 and U-48 vacuum tube microphones built in the 1950s, which their producer George Martin has written were his favorite microphones.

From January 1964 until November 1968, when Abbey Road Studios went to transistor-based pre-amps, these mics were almost always plugged into the tube pre-amps in the desk of the studio control room. That desk was called the REDD.51, and the pre-amps inside it were designated the REDD.47. REDD stood for Recording Engineering Development Department, EMI’s “skunk works” for in-house studio technology R&D and construction. In addition to their use as microphone pre-amps, in July of 1968, when John Lennon demanded a massively distorted electric guitar sound for a song he wrote called “Revolution,” Beatles engineer Geoff Emerick daisy-chained two of the REDD.47 pre-amps together, cranked up the gain, plugged in Lennon’s Epiphone Casino semi-hollowbody electric guitar, and created a roaring chainsaw tone that remains legendary to this day.

Since the early 2000s, Chandler Limited of Iowa has been issuing EMI-licensed and tested recreations of the components that graced Abbey Road Studios in the 1960s and ‘70s. In 2015, Chandler issued their reproduction of the REDD.47, employing a recreation of the unit’s two-tube pre-amp circuitry in a modern two rack-space unit, with a few added features for modern recording. On the spartan rear of the unit are XLR inputs and outputs, an input for the unit’s power cable and a fuse. On the front is a switchable 1/4-inch jack for an electric guitar or bass, and knobs for gain, rough output, fine gain set, and switches for an 20db pad, polarity, phantom microphone power, and the main power switch. There is also a switchable rumble filter for reducing unnecessary low noise, which will likely need to be high-passed out of final lead vocal anyway.

Inside the REDD.47 are two vacuum tubes (or “valves” in British parlance), an EF86 and an E88CC. So what does it all sound like? As Sound on Sound’s Hugh Robjohns wrote in his detailed review of the unit back in December of 2015:

Chandler’s REDD.47 is an impressive update on a revered ‘classic’. It’s almost unique, as there have been precious few hardware incarnations of EMI’s first modular amplifier until now. It has a very different character from that of Chandler’s other classic EMI preamp, the silicon-transistor TG2 preamp from the 1970’s-era TG console.

My impression from memory, is that the REDD.47 sounds larger but noticeably softer through the bottom end, whereas the TG2 is much more solid and ‘contained’. Both share a dynamic, punchy mid-range character, though, and the REDD adds a subtle but attractive grainy character at the top end. Overall, its vintage ‘valve and transformer’ sound character is quite evident, and very musically pleasing, yet this is no one-trick pony and its technical performance is perfectly adequate for modern recordings nearly 60 years on: it has the versatility to deliver fine, clean and delicate, or strong and colourful, character equally well. Perhaps this shouldn’t come as a surprise: it was, after all, originally designed to be used in consoles employed in Abbey Road’s classical Studio One as well as pop sessions in Studio Two!