English Acoustics Stereo 21c stereo power amplifier
- Alan Sircom
- Mar 2022
Alongside the recent resurgence in all things audio, there has long been interest in classic audio electronics. As Hi-Fi+ aims to be truly global in its outlook, those classic designs of the 1950s and 1960s pose a slight problem as most of them didn’t travel. A classic Dynaco ST-70 has less ‘resonance’ with English classic audio collectors, and a Saville Double-Six is not high on the wish list for American enthusiasts. However, the input of Japanese audio obsessives from the 1980s onwards changed much of that; they recognised much of what was good from our collective pasts, and frantically bought it all up. As a consequence, some of Leak’s ‘point one’ power amplifier designs – such as the TL/10, TL/12 and 12+ and the Stereo 20 – were some of the brightest stars in the classic hi-fi firmament. Also as a consequence, mint condition versions are now rare and command a good price. Fast forward to 2021 and there is still a lot of mileage in those circuits. A Wiltshire start-up called English Acoustics has taken one of those designs – the Stereo 20 – and lovingly recreated it, with more than a sprinkling of 21st Century sensibilities. The result is the English Acoustics Stereo 21c. ‘Made in England’ is often stretched beyond all credulity, but this time it’s entirely genuine, with little more than the terminals sourced outside the shores of ‘Blighty.’
We can’t look at the English Acoustics Stereo 21c without looking at the amplifier upon which it is based; the Leak Stereo 20. Engineer Harold Leak founded H.J. LEAK & Co back in 1934 and from the outset, the company made high-performance audio equipment. However, it was in the post-war era that Leak really took off. The company’s Type 15 amplifier of 1945 was the first commercially-available amplifier to feature a push-pull, negative feedback design (this was about the time when D.T.N. Williamson published his ground-breaking circuit design in Wireless World). Leak’s initial design was soon followed by a series of ‘Point One’ models (the name taken from their then-exceptional 0.1% distortion figure). In 1958, the world of hi-fi was all about the move from monophonic to stereophonic sound, and Leak launched the Point One Stereo 20 chassis in that year. This power amplifier was one of the first to include two channels on a single chassis and used three ECC83 driver valves, a single GZ34 rectifier valve and two EL84 valves per channel, delivering 10 watts per channel. A subsequent transformer change and slightly higher operating bias in 1961 eeked out a little more power from the circuit, and it’s this 14 watt per channel circuit that is lovingly recreated and updated here.
English Acoustics itself began in 2018, with ex-BBC engineer Peter Farrow as its Chief Technical Officer and Jordan Jackson as Chief Operating Officer. One of the company’s first projects was a restoration of a Leak Stereo 20. This itself is an understatement; this isn’t ‘restoration’ in the ‘repair, rewire, revalve’ sense… it’s more like the sort of Concours d’Elegance rebuild one might get when you throw above-the-odds money at a company like Aston Engineering. But, soon after one such restoration, Farrow and Jackson (which sounds like they should be making high-end wallpaper) realised they could engineer a new Stereo 20 from scratch, and add a few improvements along the way. This is a difficult task, as it’s easy to move from ‘curation’ to ‘homage’ to ‘pastiche’, but fortunately, English Acoustics stayed firmly on the side of the angels.
Of course, making such a design comes with its own baggage; those of us who have experienced the Leak Stereo 20 are going to struggle not to see a carbon copy of that amplifier. Especially if that experience is rose-tinted memory. Let’s be truly honest here; for all its sonic excellence, the Leak Stereo 20 was a bit ‘raw’ by today’s standards in finish terms. A folded metal chassis with sharp ends and corners are not that popular today (damn snowflakes and their dislike of bloodstains). Similarly, creating a chassis without a baseplate in 2021 might not end well from a legal perspective, given there are some really high rail voltages in all that exposed wiring. So, in that part alone, the Stereo 21c makes for a more refined design, with its nicely finished, well rounded CNC milled chassis and baseplate with the company brand used as ventilation. Then there’s the finish itself; Leak made them in a rich shade of dark gold, but that wasn’t the thickest coat of paint in history. Even those that spent most of their lives cocooned in a closet ended up looking beaten up with chipped paint and lost logos. English Acoustics would have upped the game if it had reached for the Hammerite, but instead has made the finish a feature. The range of finishes is being added to all the time; as we went to press, the company announced a ‘flip-paint’ version that varies between blue, purple, and green depending on the angle of view… a colour scheme popular with sea monsters and their friends and family, no doubt! But in all seriousness, the review sample came in a rich British Racing Green the depth of which you wouldn’t find on a Bentley made this side of the 1930s. This contrasts nicely with the Art Deco English Acoustics logo, which occupies the same space the Art Deco logo of Leak once lived. There are twelve standard colours, with two additional finishes unique to stores (the Navarra Blue exclusive to PJ Hi-Fi and the Porsche Perlmutt Weiss finish unique to Art+Sound) and custom finishes in their infinite variety command a £500 premium.
The amplifier itself is wired point-to-point with discreet components on boards, just like the original, although what used to be a series of small mica boards connected by low-cost wiring is now a single board with beefy etched tracks connecting the sections. The wiring connecting the valve seats to the board – and the board to the transformers – is immaculately ‘dressed’ (not dissimilar to a Naim amplifier), no loose assemblage of wiring loom here, everything is laid out like a Frank Pick tube map. That, together with the considerably more rigid tolerance of high-grade components on the circuit (even down to the silver mica caps of old; they could never be made to this precision in the 1950s) makes the Stereo 21c perform like a ‘blueprinted’ version of the Stereo 20.
Even those two large, potted caps on the top plate are given a touch of English, with the screen caps hiding some exceptionally high-grade caps stripped back to fit perfectly; given you could shine a light into the amp on most older samples on this part of the top-plate, this is an improvement to both looks and safety. On the subject of safety, this is where English Acoustics parts ways from the 60+-year-old design. First, it has a soft-start round power button (against the ‘plug and pray’ nature of the original). Then it has both thermal and motion-detection cut-outs, so tubes about to blow or someone knocking the amp off its perch is unlikely to cause any kind of electrical crisis. This is useful in a product that doesn’t include a valve cage, even if this puts the Stereo 21c somewhat at odds with current thought regarding valves. That being said, I can’t think of an easy way to create a cage for these valves without materially changing the aesthetics, and not every brand follows this edict anyway.
OK, so Leak fans will argue there was a form of thermal cut-out in the original Stereo 20 in the shape of a sacrificial resistor. Personally, I prefer a more modern approach to one that requires a soldering iron. There is also a digital display close to the power socket to tell you how many hours you’ve racked up on a given set of tubes. This is handy because the amp can do with a few dozen hours of new-tube shakedown before it gets into its stride. Moreover, given the quality of the sound the Stereo 21c produces, it might be good to know just how long you’ve been listening and when it’s time to get more Tung-Sol tubes.
Bringing the best of the 1960s into the 21st century needs some addressing. First, there was an operational ‘quirk’ to the Stereo 20 that is echoed here; the phono connectors are on what might seem like the front right of the amplifier and the logo runs along the right-hand side, meaning the amp is designed to sit at 90° to most designs. More importantly, while a 14W stereo amplifier will meet (and exceed) many listener’s demands, loudspeakers with more challenging sensitivity and impedance figures will result in a smaller, quieter or even thinner sound (of the line-up of small loudspeakers I regularly use, the 21c fared well with the KEF LS50 Meta, was fine (but no roof-raiser) with the Audiovector R1 Arreté and didn’t like the upper-bass impedance dip of the Wilson Audio Duette Series 2 at all.
In truth, how the Stereo 21c sounds is how everyone might expect a Stereo 20 to sound, except with a few minor improvements to frequency extension at both ends. This is no bad thing; the Stereo 20 was one of the sweetest sounding, most inviting amplifiers of its time, with very good bass and a slightly congested high treble. That midrange was beautifully enticing, natural, and projected perfectly into the room with an articulate and ‘bouncy’ presentation. And the Stereo 21c does nothing to change the shape of that midrange, instead just making the bass a little bigger and more ordered, and the treble a tad (an Imperial measurement) less uneven and more extended. In short, it’s a Stereo 20 that sounds a bit better and a bit more ‘now’. Who’d have guessed it?
English Acoustics’ Stereo 21c retains much of the original’s musical warmth, grace and finesse. It almost invites you to play vocals through it, just to showcase that ‘just the right side of lush’ presentation that grabs you firmly by the feels. My first draft of this review just kept saying ‘beautiful’ time after time, but there’s a good reason for that; that sound just draws you in and makes everything you play sound, er, beautifully beautiful with an added side order of beautiful.
The Stereo 20 covered its tracks well; it took a lot of listening to begin to hear that slightly rolled-off top-end, especially when playing with the equipment and recordings of the time. However, with brighter metal dome tweeters, that top-end never quite sounded fully extended into the ‘Piccolo Symphony for Dogs’ level. Fortunately, whether it’s the latest grade of components or 60+ years of transformer development in the driving seat, the Stereo 21c sounds far comfier and soaring in the upper registers. I’d still argue the Stereo 20/21c is not best matched to metal dome tweeters, in the same way, this is not meant to be partnered with low-sensitivity loudspeakers with an impedance plot like a map of the Himalayas.
Play to its strengths, though, and this warm, enticing sounding and (here it comes again) beautiful sounding amplifier sings sweeter than almost anything made today. While this is a high-precision, high-fidelity (in the old-school sense) amplifier, it’s not the kind of soulless beast designed to reproduce test tones. It’s a musical instrument from the classic era of the best in British audio, brought right up to date. English Acoustics is more than simply a recreator of audio antiques; the company has a Stereo 41c and an all-valve preamp waiting in the wings. Further down the line, English Acoustics will have a range of monoblocks and other stereo amplifiers that break away from the 21c look. But with the Stereo 21c, English Acoustics took a classic and made it their own, and in the process helped remind us what good hi-fi is all about!
- Type: stereo valve power amplifier
- Power output: 14W/channel ultra linear
- Valve complement: 3× ECC83, 4× EL84, 1× GZ34
- THD+N: Less than 0.1%
- SNR: Better than 90dB reference 1W
- Frequency response: +/-1dB 13Hz–35KHz (full power bandwidth)
- Finish: CAD designed steel chassis with laser cut details. Transformer endcaps CNC machined from billet aluminium. Automotive-grade metallic paint finish available in large range of colours.
- Valve sockets: Ceramic, gold-plated
- Fixings: Custom English manufactured
- Wiring: Point to point hand-wired valve sockets with lead free silver solder
- Transformers: hand wound transformers locally in Wiltshire, England
- Protection: Thermal, vibration and tilt safety cut out
- Power Inlet filter: Medical grade
- Remote power on: available as an option
- Display: Digital LCD hour meter
- Finish: various
- Price: from £5,000
Manufacturer: English Acoustics
Tel: +44(0)1249 736180
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