TEAD The Vibe line-stage and The Pulse power supply
By Roy Gregory
The line-stage (or line-level preamplifier to give it its full, slightly portentous title) is possible the most misunderstood and maligned component in the audio chain. It used to play second fiddle to its in-built phono-stage, an afterthought added to allow taping and tape replay as well as listening to the radio, whilst you weren’t doing the far more important business of playing records. Then, along came the CD and suddenly a new focus was thrown on the performance of the line-level section in any pre-amplifier. Soon, pre-amplifiers started to appear in which (shock-horror) the phono-stage was an optional extra! But even then, as the line-stage finally stepped forward into the limelight, its thunder was already being stolen and its rôle undermined by the emerging interest in ‘free’ (or nearly free) alternatives, like passive volume controls/pre-amps (such as the ModSquad Linedrive) or CD players and DACs with variable outputs, often executed in the digital domain. The very fact that such options were even considered viable suggests just how low the Line-stage’s stock had fallen – and how poorly executed many of the then current line-stages were…
On the face of it, the line-stage’s job is considerably easier than that of the phono-stage (which often has to amplify the signal from a cartridge many hundreds of times) or the power amp (which has to contend with the obstinate and complex nature of the speakers it’s connected to). The line-stage simply has to offer a welcoming environment to incoming signals, set level and deliver a robust output. In other words, it has to offer a stable reference point at the heart of the system. But – and it’s a big but – it has to do that without leaving grubby finger marks all over the merchandise. That means it can’t add noise and it can’t limit, compress or diminish the signals passing through it. It’s the ultimate example of “nothing added and nothing taken away.” As anybody who has attempted yoga will confirm, often, sitting still and doing nothing is far harder than it looks. Doing it with the anchored sense of calm authority necessary to convincingly reproduce wide-bandwidth musical programme requires yogi-like levels of stability and inner peace. Which helps explain why there are fewer really world-class line-stages than any other category of component – and why many of them are seriously expensive.
However, there are exceptions and for many years, The Tom Evans Audio Design Line-stage (The Vibe) has been amongst the most affordable. Its longevity alone makes it worthy of attention, but the thing that really sets it apart is its performance, its sonic invisibility and its ability to pass a signal without reducing its dynamics or muddling its temporal integrity. Like other TEAD front-end components, it is solid-state and IC-based (the power amplifiers are tube-output hybrids). Before that has you throwing your hands up in horror, just remember that it ain’t what you use, it’s the way that you use it that matters. There are plenty of truly dreadful tube pre-amps to counterbalance the odd good one from the likes of cj or CAT, plenty of awful, discrete solid-state devices to contrast with the likes of CH or Koda. And, as The Vibe so emphatically demonstrates, op-amps can be used to excellent effect – if you know what you are doing… After 35-years of working with the technology, it should come as no surprise that Tom Evans is a master of this art. As he points out, not all op-amps are created equal. He uses carefully selected silicon, often scratching off the model numbers to preserve their anonymity, incorporating them into the phase corrective circuitry he first developed for the Michell Iso. He was one of the first to use multi-layer circuit boards, with full-area ground planes to reduce noise, and he has worked constantly to improve the noise performance of the proprietary Lithos regulators that power his circuits. Recently upgraded with Lithos 7.4 regulators to full Mk.1.7 status, The Vibe is long overdue a re-visit review, assessing how it stacks up against the current competition.
“E-lim-i-nate the negative…”
The phrase “Less is More” is overworked when it comes to audio. It’s useful in a vague and rather general sense, but as soon as you start to look at products or systems in detail you soon realise that far from helping understanding, it can lead us to ignore or eliminate essential elements – like the line-stage itself, but also important parts or constructs within products and circuits. More pertinent is the goal of “making everything as simple as possible – but no more simple than that.” The Vibe is an object lesson in exactly that, a near perfect balance of performance, cost and value, a pared back box that does exactly what you need it to – and absolutely nothing else. So, no balanced circuitry, no network connections, no unity gain option, no user adjustable input or output parameters: In fact, no unnecessary facilities or functionality at all. Just the simplest operational requirements exactingly executed, in a circuit that’s as complex as it needs to be – but no more.
