‘The Vibe’ has garnered a ‘cult’ following right around the world, so Greg Borrowman was eager to get the first one to arrive in Australia for review.
Tom Evans Audio Design started up in 1984 as an ‘electronics designer for hire’ after its eponymous founder retired from a career in military electronics. Evans’ first commission was from London’s J.A. Michell Engineering, and the result was the famous Iso phono stage. Michell was so pleased that the relationship continued, bearing fruit in the form of the Argo pre-amplifier and Alecto power amplifier. When Pioneer (Great Britain) became aware that the Eikos was actually a Pioneer PD-904 CD player that had been extensively internally re-worked by Evans and re-badged, Evans found himself with a five-year contract to develop a range of Pioneer products exclusively for the UK market. In between, Evans found time to design ‘The Groove’, which he described as ‘the ultimate performance phono stage’ and then a budget version, the MicroGroove. Both are now also available in various improved ‘Plus’ versions.
Tom Evans’ ‘The Vibe’ stereo preamplifier is a tad unusual amongst pre-amps in that it uses a passive 24-step DACT attenuator to control volume. This not only allows precise volume setting, but also enables volume to be adjusted in equally precise—and repeatable— increments. Perhaps even more importantly, the use of an attenuator means that channel balance is maintained within ±0.05dB at any setting of the attenuator. If you’re wondering what a ‘DACT’ attenuator actually is, the letters comprise a rather tortured acronym for Danish Audio ConnecT, which is the company that manufactures them (together with a range of internal and external electronic parts) in Denmark. And if you’re no wiser as to what a stepped attenuator is, it’s an array of surface mount metal film resistors mounted on a gold plated spiral track. The main benefits of using a stepped attenuator rather than a standard rotary potentiometer are lower distortion, wider bandwidth, shorter signal paths, stunningly accurate (and repeatable) volume settings and far lower noise.
The all-important five-position input source switch is apparently sourced from one of Evans’ military mates, being a switch that’s more often used in battlefield communications equipment. That ‘mate’ is UK specialist manufacturer WASP, which achieved recognition in the early 70s as an innovator in the design and manufacture of rotary switches for the professional, military, instrument and telecommunications markets. The company has since expanded into the design and manufacture of sophisticated membrane switches and touch-screens.
The Vibe is unique amongst preamplifiers in that its voltage regulation is accomplished by Tom Evans’ own unique ‘Lithos 7’ regulators… though admittedly these are also found in other Tom Evans designs. I could not find any technical information concerning the operation of the Lithos regulators, since Evans does not seem to have applied for a patent, presumably to protect his intellectual property. His claim is that his Lithos voltage regulators are ‘53 times faster, 1,000 times quieter and 5 decimal places more accurate than the previously best regulators available.’