Posted on Thu, 08 Jun, 2017
Posted by Bob

The Valve Amplifier: controversial, emotional, impractical even, but always inspirational. Whichever way one looks at it, Valves, and Valve Amplifiers, are very special and unique.

Today on The Audio Affair blog, it’s time to pay respect to the electronic component which started it all, The Valve, or, as they’re known elsewhere in the world Vacuum Tubes, or simply ‘Tubes’


The Valve – Amplification Genesis

The invention of the Valve in the early part of the 20th Century was the invention which made amplification possible. It was an incredible component which dominated the world of electronics right through into the 1960s.

By the ’60s however, Valves were increasingly being phased out for their modern counterpart, Transistors; transistors were smaller, lighter, ran cooler, used much less power, were more reliable and much more robust. Our modern world wouldn’t be possible without the transistor.

Why then, in 2017, are you reading an article about Valve Amplification, using a computer filled with literally billions of transistors? Well, as with all things involving affairs of the heart, it’s never quite so simple, is it?

EL34 valves in use

The Valve Sound

There’s a very special *something* about audio which has been passed through Valves. Orchestral strings take on a unique smoothness and air, cymbal crashes burst with a brilliant radiance. As for the human voice amplified by Valves? Prepare for goosebumps.

So what’s actually going on inside a Valve Amplifier, and why do they sound so special? Why does a certain cult of Audiophile worship these electronic antiques, eschewing modern semiconductors?

Valve Amplifiers typically display a few quirks and idiosyncrasies, unique to Valve amplification; debate has raged for decades as to whether these are desirable qualities, however, there’s no doubt they’re a big part of ‘the valve sound’.

Happy Accidents

Distortion, so we’ve been told for decades, is the utter antithesis of Hi-Fi listening. Our equipment should be a transparent window to the original recording.

What if our equipment makes that original recording sound *better* though? More enjoyable? More exciting? More alive! This is very much something one can associate with a good Valve Amplifier.

This effect is partly down to a Valve’s unique quality of producing even order harmonics, especially when driven hard. In contrast, solid state devices tend towards odd order harmonics, which are not as pleasing to the ear.

The interaction of a valve amplifier with a connected loudspeaker is also a big part of the magic. Valve amplifiers exhibit a looser damping to the vibrations of a loudspeaker’s cone; this typically results in a warmer, more resonant low end. A very different feel from solid state amplification.

Classic Designs

So, you’ve read this far, digested the information, and rather than run away in disgust at these archaic old pieces of electronics, you’re now feeling the desire to have your own piece of thermionic joy.

Whilst it’s true that there are some vintage amplifiers out there capable of fantastic performance even now (Quad, Leak, Dynaco, Sugden etc.) buyer beware!

Owning a genuine, Vintage Valve Amplifier is akin to owning a Classic Car – something of a persistent labour of love which requires a dedicated owner. Many components will be well past their best by now and in urgent need of replacement.


The Leak Stereo 20 – A classic Hi-Fi design

Modern Valve Amplifiers

Thankfully, for the modern Audiophile desiring the Vintage Valve Sound, there has been a modern renaissance in Valve Technology and Valve Amplifiers.

Some of these designs are modern recreations of classic amplifiers, whilst others offer new designs based on classic amplifier topologies, or in some cases, radical new designs based on obscure valves.

Let’s take a look at three of the current ‘big names’ in Hi-Fi Valve Amplification…


Formed by Peter Walker in 1936, Quad formed one of the ‘big three’ British Hi-Fi companies along with the extant Wharfedale and the sadly extinct Leak.

The product which (arguably) put Quad on the map, was their Legendary Quad II Monoblock Power Amplifier, Introduced in 1953. Its simple yet efficient design contributed to an excellent sounding amplifier, which is still revered and coveted today.

Thankfully, since 2005, the Quad II has been available, once again; the Quad II can be purchased as a faithful ‘re-issue’ of the KT66 powered Monoblock original, under the banner of the Quad II Classic, which is sold as a stereo pair of Monoblocks.

Quad II Classic Valve Amplifier

Quad also offer a number of new & re-imagined Valve Amplifier designs, some of which are based upon the venerable Quad II. The Quad II Forty and Quad II Eighty, supplant the Classic’s KT66 output valves for a duet or quartet of KT88 output valves, for a significant increase in output power.

Looking for an integrated Valve Amplifier? Quad offer the Quad II Classic Integrated – essentially a pair of Quad II Classics coupled to a newly designed pre-amplifier, all wrapped up in one chassis.

Quad also offers brand new designs, in the form of the PA One and VA One Headphone amplifier and Integrated Amplifier, respectively. The latter even offering Bluetooth connectivity. For those looking for a valve preamplifier to accompany their Quad II’s, there’s the QC24P.
Quad Valve Range

Unison Research

Unison Research embodies a company very much a part of the valve Renaissance. Formed in 1987 in Italy, Unison Research amplifiers are both a sonic and visual treat; very much an item you’d be proud to display in your living room.

The Unison Research range of Valve Amplifiers comprises everything from simple, single-ended integrated amplifiers such as the Simply Italythe ‘beefy’, KT-88 based Sinfonia Integrated Valve Amplifier, right up to the gargantuan  Absolute 845 Integrated Valve Amplifier.

If you’re looking for a real ‘Statement Piece’ of home audio with that special ‘Valve Magic’, one could do much worse than to investigate Unison Research’s spectacular range of Valve Amplifiers.

Unison Research 845 Absolut

Unison Research’s incredible Absolute 845 Integrated Valve Amplifier

Icon Audio

Relative upstarts Icon Audio began manufacturing Valve Amplifiers and associated Hi-Fi equipment in 1999. Icon Audio wears their influences on their sleeve, stating classic British & American Valve Amplifier designs by manufacturers such as Quad, Leak, Dynaco & McIntosh to be strong influences.

That’s very much apparent in designs such as the Stereo 20PP, a modern update on the classic Leak Stereo 20, a sought-after vintage classic, long since out of production. In contrast to the four-figure price tag the originals often fetch, the Stereo 20PP is priced at a *highly* reasonable £799

Where the Leak original required a specific, rudimentary preamplifier to be connected in order for the amplifier to function, the Stereo 20PP incorporates a basic pre-amplifier along with headphone amplifier.


Affordable recreations of classic amplifiers aren’t all Icon Audio are about, however. Icon Audio’s range include valve phono stages, valve audio buffers, high-efficiency loudspeakers and incredible one-off, unique designs such as the MB81, based around a Russian transmitting valve!


If you’re in any way tempted to take the plunge into the wonderful world of the Valve Amplifier, don’t hesitate to drop us a line at Audio Affair. We’d be very happy to advise you on the best amplifier for your budget and application!

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