English Acoustics Stereo 41c power amplifier

The Leak Stereo 20 was an engineering masterpiece from the Golden Age of Audio. Recently, English Acoustics lovingly recreated—and subtly updated—the Stereo 20 design in its first product, the Stereo 21c. 14W per channel of delightful low-distortion valve-based audio might have been a joy in 1958. Things have moved on. More power is needed today, and the new English Acoustics Stereo 41c power amplifier is the answer.

The Stereo 41c boosts output to a more 21st-century chummy 30W per channel. This is thanks to its use of EL506 output tubes and bespoke transformers to match. It is the perfect blend of old and new. It still uses the same classic circuit design and layout that proved popular 65 years ago. However, it is built to today’s high-end standards. It also includes features unavailable to Harold Leak and the team in the 1950s.

To begin at the beginning

It’s worth a quick revisit to the Stereo 21c as a perfect introduction to the Stereo 41c. This is because the Stereo 21c sets out what English Acoustics is about. It’s the brainchild of ex-BBC engineer Peter Farrow (now English Acoustics’ Chief Technical Officer). The earliest projects at English Acoustics were to undertake restorations of classic valve amplifiers. A love for the Leak Point One design is almost a certainty because it’s a joy to work on.

Most companies at this point would operate as restorers, and a small army of proud ‘bodgers’ does just that. But English Acoustics is not ‘most companies’. Peter recognised the Point One circuit as one of the most outstanding designs of its time. But that time began in the late 1940s. The primary amplifier circuit didn’t need improving, but the application and implementation could benefit from generations of technological development. It also features modern safety features. These were the stuff of B-Movie sci-fi in a time before transistors.

The company’s first restorations prevent the absolute purists from considering these developments heresy. Among those who enjoy Leak’s Point One designs, English Acoustics was the brand that went the extra mile. Your restored Stereo 20 left the company in a better state than when they left Leak’s old West London factory 60+ years ago. But Farrow realised there is only so much you can do with the original Stereo 20.

Wiggle room

Leak built the Stereo 20 to the highest standards of its day. But ‘highest standards’ still had some wiggle room. We live in an era when a 12″ wide chassis can’t be “give or take an eighth of an inch or so.” The Stereo 20 pressed and folded chassis no longer ‘cuts the mustard’. Also, a riot of colour options replaces the limited palette of 1960s enamels. This led to one of those ‘why don’t we…’ discussions that included what a manufacturer in the 21st Century would need to do to bring an amplifier launched in 1958 (and based on a circuit from the mid-1940s) up to code.

This is no simple task, as you risk undermining the original’s performance and aesthetics. So, English Acoustics’ first product was an updated Stereo 20. It uses a chassis that is more than pressed steel and stove enamel. More importantly, it adds sophisticated modern features like a digital thermal cut-out and an orientation sensor. It also uses modern components throughout, including recreations of classic components when the newer ones either do not make the grade sonically or are unavailable (such as 0.25µF paper-in-oil capacitors).

English Acoustics Stereo 41c: More power!

The Stereo 21c is a popular amp, but 14W is not that powerful by today’s standards. Paradoxically, modern loudspeakers are more efficient than similarly sized acoustic suspension counterparts of the late 1950s. Leak designed the original Stereo 20 with efficient corner horns in mind. While that original can make nice sounds with a well-matched pair of loudspeakers, it’s not a roof-raiser. Even boosting that output to 30W helps, as it raises the amplifier’s headroom and widens its circle of loudspeaker friends.

There are a lot of options English Acoustics could have called on. Harold Leak’s original Point One circuit (so named because it offered a then-ground-breaking 0.1% harmonic distortion) was implemented in various mono and stereo chassis. English Acoustics could have made a direct ‘lift’ of the more powerful Stereo 50 or Stereo 60, but in some respects, these also reflect the market at the time.

More than 20

While they were both more powerful than the Stereo 20, they were more expensive and sold in tiny numbers for the era. Consequently, the Stereo 50 and 60 amps used a single 5AR4 rectifier. This was possibly a cost-cutting exercise but arguably sapped dynamic headroom. So, when it was English Acoustics’ turn to raise the power output, it didn’t go the obvious route of just calling on one of those bigger Leak Point One designs; they were simply the inspiration.

In the Stereo 41c, the story begins with one 12AX7/ECC83 double triode used in the input. This is met by an ECC82 per channel as a gain stage, feeding a pair of EL506/7868 pentode. Each channel has its own GZ34S/5AR4 rectifier valve. In-house-designed transformers are a big part of the ‘English’ part of English Acoustics. Almost everything in the English Acoustics Stereo 41c (and all other English Acoustics products) is ‘local produce’; not simply in the UK. Many of the components are made as close to English Acoustics’ Wiltshire base.

Not only flag waving

This isn’t just a flag-waving exercise; one of the things the English do exceptionally well in the 21st Century is small-scale precision engineering. The UK might not be the centre of the manufacturing world (and arguably hasn’t held that title in more than 150 years). Still, when it comes to making high-precision, limited-run, cost-no-object components, there’s a reason why so much Formula One engineering is UK-based. English Acoustics leveraged the same ‘sans pareil’ approach used by anything from Purdey shotguns to Red Bull Racing.

Of course, the exception to this is the valves themselves, and one of the big problems with modern valve designs is sourcing products that, in recent years, have been made in Russia. The sample I received used Electro Harmomix 7868s and used a nine-pin base; fortunately, Tung Sol also makes a 7868 and New Old Stock Brimar EL506s are available. JJ Tesla makes a 7591 with the same internals but sports an octal base. Base converters are available, and if the source runs dry, English Acoustics will swap over to the octal base for 7591s.

The most prominent part of the amp, however, is the finish, and the colour options are surprisingly fitting. You can see a clear difference when you see the English Acoustics models with the same gold finish Leak made its own. The enamel finish was good for its time, but we’ve moved on a lot. Compare that enamel to the rich, unblemished satin gold sheen of the English Acoustics.

Synthwave Daleks

This is slightly more important than on many power amps because the top plate is a larger canvas than usual. The Leak and English amps have their tubes running down either side of the chassis, leaving the central part of the top plate a blank canvas. That doesn’t mean it should have an Old Master between the bottles, but the finish must be perfect. And yes, having a wealth of colour options opens a whole world of decision-making, especially as English Acoustics’ Downton preamp is similarly made to order. You could conceivably have the two in contrasting vivid Synthwave colours or decked out in dark greys and black like 1960s Daleks.

I’m not stressing the paint finish to pad the review… honest. But we have grown used to having loudspeakers in any colour you might want. The same options in audio electronics are rare, with Perreaux and English Acoustics being the exceptions. Maybe it’s time more companies took the hint provided by English Acoustics.

Sound quality, job done!

In many respects, the amplifier reflects a time when sound quality was a given and merely a function of more or less power and distortion. No one who bought a Leak Stereo 20 back in 1958 was concerned about how it sounded. We’ve moved on, but in a way, the English Acoustics Stereo 41c shows that we might have been over-obsessed with nuances in audio performance. This amplifier works exceptionally well. It’s insightful, detailed, and has outstanding image properties.

For its 30W, it is deceptively powerful and – as with the original requirements for a Stereo 50 – is a fine partner with modern stand-mounts and floorstanders. Moreover, because those transformers are designed specifically for the task, the amplifier is excellent at the frequency extremes. Iit gives excellent bass and, unless you are using a pair of loudspeakers designed deliberately to torture amplifiers (something with a one-ohm load impedance dip, for example) or using it to fill a room the size of Norway with death metal played at ‘gig’ volumes, the Stereo 41c is a surprisingly powerful amplifier partner.

Not ugly, creamy

Perhaps best of all, if you push it into ‘naughty’ levels, it just goes ‘creamy’ rather than ‘ugly’. I had a few friends around, and the game of musical ping-pong got a little heated when playing the title track of The 1975’s I Like It When You Sleep for You Are So Beautiful yet So Unaware of It album. It’s a lovely 2016 slice of ‘ambient chill electronica meets muted chorus’ and fills a room. I realised I was playing it at the sort of ‘refreshed’ levels you get to after the second bottle of port goes around.

Other lower power amps go hard and angular sounding as they hit their distortion limits, but this smoothed things off, and the creamy warmth made the music sound like it was flowing well. Only the next day, when the port’s ‘head-gout’ kicked in, did I notice just how well the Stereo 41c coped.

Refinement going forward: English Acoustics Stereo 41c

What I like about the Stereo 41c from English Acoustics is what I like about the Stereo 21c and the Leak Stereo 20. It’s never a pushy, forward sound. It’s not over-relaxed sounding, but music is never shoved at you, neither in soundstage nor tonal balance. The music has a sense of lightness, richness and relaxation. That works just as well when playing room-clearing Schoenberg as it does with room-filling Charlie Parker. You are just more engaged with the music.

English Acoustics has a small but intelligently designed lineup. It has two power amps and a valve-based preamplifier called Downton, available to order. The company has transitioned from ‘restorer’ to ‘manufacturer’ well. In the Stereo 41c, English Acoustics has made more than an amp Harold Leak might have been proud of. This is a beautifully made, sensational-sounding 30W power amplifier that is designed to last a lifetime… or two!

English Acoustics Stereo 41c: Technical specifications

• Type dual mono valve power amplifier
• Power output 30W/channel ultra linear
• Valve complement 1× ECC83, 2× ECC82, 2x 7868, 2× GZ34
• THD+N Less than 0.1%
• SNR Better than 90dB reference 1W
• Frequency response 8Hz–68KHz (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 £7,500, $10,196

Manufacturer

English Acoustics

www.englishacoustics.co.uk

+44(0)1249 736180

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