Past Masters: NYTECH AUDIO CTA252XD II

Posted on 27th May, 2020

Past Masters: NYTECH AUDIO CTA252XD II

David Price tells the story of one of Britain’s most eccentric, long-lost hi-fi products…

There was a time in the nineteen seventies when British hi-fi magazines were recommending that people seeking the best mid-priced amplifier available, should in fact buy a receiver. Such was the performance of Nytech Audio’s legendary ‘Calculator Tuner Amplifier’, that many regarded it as a brilliant integrated that just happened to have a tuner bundled in. And yet that ‘free’ tuner also sounded spectacularly good, with many FM aficionados saying it’s still one of the best available, even today.

The CTA252 showed a remarkable resemblance to the large, mains-powered ‘desktop’ calculators of the early seventies. The unit was distinguished by its top-mounted buttons, offering four FM presets, filters and loudness controls, plus sliders for volume, balance, bass, midrange and treble. Above these, set behind a perspex window rather like a calculator’s display, were three meters – for signal strength, tuning and a frequency indicator. All glowed a subtle green, just like the dashboard of a car of that era. 

Nytech CTA252

THE RADFORD YEARS

Although synonymous with the seventies, the Nytech was really a product of the nineteen sixties – because those were the formative years of its founder, Richard Hay. He first worked for Arthur Radford and Arthur Bailey, having just graduated from Southampton University in 1967 with an electronics degree. Richard had always loved music, but his first passion was aerospace and he’d dreamed of a future with Hawker building fast jets, his boyhood hero being Barnes Wallis.

Radford Electronics Ltd. was a serious engineering company that gave Richard the chance to shine, later becoming a Chief Engineer working alongside Arthur Radford and Dr Arthur Bailey. He helped to move the company away from its ageing range of valve amplifiers, and worked on transmission line loudspeakers, microphones and mixing desks. Richard loved valves but saw the writing on the wall, and knew transistors were the coming thing.

THE NYTRONICS YEARS

In 1972, Richard – alongside engineers Dave Alner and Paul Hamblin – left Radford to start Nytronics Ltd., a company backed by Electroustic Ltd. and owned by brothers Jeff and Nigel Thornton, which supplied electronic components to manufacturers such as Radford. Hay had discussed the possibility of starting a British hi-fi company with Jeff in the late sixties, and this was the result.

Electroustic brought forward a contact with Laney Amplification, and it was agreed that Nytronics would design a tuner/amplifier for them called the TLA200, under the brand name of Thomas Laney Audio. Dave Alner had left Radford in 1971 to work for Bristol-based Digicon and started doing electronic design work for this in the evenings and at weekends. Meanwhile, Richard was charged with the task of finding suitable premises in or around Bristol, and came up with an old brickyard stable in Portishead which needed extensive renovation. He left Radford to start on this, along with Paul. After six months the site was nearly ready, so Dave resigned from Digicon and moved to Portishead to complete his design work and set-up the factory for testing and production. Richard became Nytronics’ Managing Director, Dave was Chief Engineer, and Paul Hamblin was Production Manager.

Nytech CTA252

At first, Richard Hay was responsible for mechanical and aesthetic design, while Dave took care of electronics design and Paul Hamblin helped in laying out the printed circuit boards, testing and production. At this time, several other projects were undertaken including an AM/FM tuner-amplifier that went on to be sold under the Woolworths audio brand. Several batches of the TLA200 were made, but the guys realised they would need a full time Test Engineer – and Keith Abbot, also previously of Radford Electronics, was recruited.

At this time, talks were going on with Electroustic about coming up with a replacement for the Philips ‘Jet Set’ system. Meetings were set up in Sweden with the company’s Scandinavian distributor, and these resulted in the design of what eventually became the Nytech CTA252. Richard Hay came up with the idea of a calculator styled device that he considered “ergonomically correct”.

Dave Alner explains that,

Being an excellent design draughtsman, Richard set about designing the case from scratch – presenting balsa wood models as he went along. We now had to find a way of getting a full featured high-quality tuner amplifier inside, so I set about designing the electronics, and Paul Hamblin helped with the PCB layout.

The result is that Dave and Paul were elevated to the positions of Technical and Production Directors, respectively.

Nytech CTA252

Visually, you might say the CTA252 was a ‘stylistic nod’ to the 1973 Canon Canola L800 desktop calculator. It had numerous facilities, including a mono switch, a tape monitor and switching for two pairs of speakers, with AFC for the tuner. Head-fi fans of today will doubtless be impressed by its twin 6.3mm headphone sockets. Launched in 1975 for the princely sum of £93, it was enthusiastically reviewed by Gordon King in Hi-Fi News magazine in June of that year – and later by Geoff Horn for Gramophone in February 1977.

NYTECH POWERS UP

The company’s name was quickly changed to Nytech Ltd. after it was discovered that there was already a manufacturer in the United States called Nytronics – and that would cause problems should they ever wish to sell their products in the USA. “Incidentally,” explains Dave Alner,

The names Nytronics and Nytech were adaptations of the word Nyquist – Harry Nyquist being an engineer that formulated most of the work on feedback analysis.

This coincided with the building of a purpose-built factory in nearby Nailsea, but this was delayed due to the builders hitting a coal seam beneath the land. The area had to be backfilled, with the attendant considerable increase in price – meaning the property had to be remortgaged. “We finally moved into the building around early 1976, producing several hundred CTA252s, mostly for the Scandinavian market, but also growing our presence in the UK”, remembers Dave.

Nytech CTA252

The CTA252 was also offered together with a turntable as the CTA1252; this was initially a West German-built PE design but was later changed to a UK-built Garrard. When production really took off, the company decided to add the option of a high-quality Compact Cassette deck, complete with Dolby Noise Reduction – but this never got off the drawing board. At the same time, Russ Andrews of Edinburgh Hi-Fi approached the guys to produce a standalone FM tuner, using the tuner head and IF strip of the CTA252, under the Edinburgh Wireless Company name. A couple of batches were made. Meanwhile, the CTA252 underwent a facelift into the CTA252XD, which contained a few specification improvements and a better phono stage, now with moving coil option.

Tragically though, Nytech Ltd. was forced to go into voluntary liquidation in 1977, when the company’s major export market – Scandinavia – went into recession. Because the UK was already in a serious economic downturn, it wasn’t possible to sell the backlog of products inside the UK, either. Richard Hay duly purchased the stock from the liquidator in 1978, moved to Chew Magna and started again.

TECH TALK

The relaunched CTA252XD (eXtra Definition) was followed in 1978 with the CTA252XDII, which got an improved toroidal transformer giving a claimed 25W RMS per side into 8 ohms, rather than 4. Later in 1979, the XDII got a slight facelift with upgraded switchgear, the DIN speaker terminals were bolstered by 6.3mm binding posts, and the ‘link’ socket round the back got a higher voltage in anticipation of forthcoming Nytech products.

Former Nytech Chief Test Engineer Phil Balaam says, “it has a very unique sound”, thanks to its AC-coupled power amplifier. “It has a capacitor in the signal path, which was and is frowned on by many on sonic grounds”, he says, “but there were some very clever ideas that got around that”.

Nytech CTA252

Physical construction was ahead of its time, using several plug-in printed circuit boards that removed the need for vast lengths of internal wiring – back at that time, many contemporary amplifiers looked like an explosion in a spaghetti factory inside. There was even a plug-in disc input stage so that moving magnet or moving coil cartridges could be easily accommodated. The CTA252’s sophisticated FM tuner head later went on to appear in the A&R Cambridge (now Arcam) T21 tuner. 

Dave Alner says that practically every stage in the CTA252 contained a trick or two to achieve the specification.

For example, the tuner head was uncompromised. We used dual gate MOSFETs for the first RF amplifier and the mixer. The oscillator was a common collector design in Colpitts configuration. The aerial was loosely coupled to the first tank circuit, the second tuned circuit was a critically coupled pair, as was the IF output which produced the correct impedance for the ceramic resonators. Nytech was one of a few UK manufacturers that designed and manufactured its own FM tuner heads.

“We were constantly told that its sensitivity was lower than most, that it would not pick up any stations without an aerial”, says Dave.

No it would not because the aerial coupling was perfectly balanced – the sensitivity achieved was around 1.8uV for 30dB quieting. The IF strip was carefully designed to produce the lowest distortion and capture ratio that the Quadrature demodulator of the CA3089e could produce. The stereo decoder was the MC1310 again, carefully adjusted to achieve a minimum separation of 40dB, with a distortion of less than 0.3%. To provide filtering of the stereo pilot tone, subcarrier and SCA signals, a dual Q multiplier circuit was employed. This – together with careful adjustment of the de-emphasis circuitry – ensured we could maintain the audio output signal within 0.2dB from 20Hz to 15kHz.

Dave is also very proud of the phono stage.

It was designed to produce an accurate RIAA response from 20Hz to 20kHz while maintaining an excellent signal to noise ratio. The first CTA 252s arranged all time constants (3180uS, 318uS and 75uS) in a conventional single feedback network. The later CTA252XD buffered a passive 75us time constant from the 318uS and 3180uS time constants which were arranged around a feedback loop.

Nytech CTA252

Much effort was expended on the power amplifier design, too. The problem was packaging – the chassis afforded just one-tenth of a litre of space, and into this, a Class AB amplifier putting out 25W RMS per channel into 8 ohms had to be squeezed. Nytech designed its own special extruded heatsink to achieve minimal thermal resistance, with maximum radiation surface area. “For its time, a true differential input stage rather than a single-ended input stage was unusual,” says Dave,

But it let us achieve exemplary distortion, bandwidth and noise performance. The design was a single-ended, capacitor-coupled circuit. Space was limited, so we did not have room for a high-value output electrolytic to achieve the low-frequency response that we wanted. Therefore we used a second feedback loop around the output capacitor to reduce the low-frequency limit. We arranged the feedback such that the amp wouldn’t go unstable into normal loads. This resulted in a negative output resistance, which is why the amplifier had such a tight bass with such a low-value output capacitor.

FAMILY TIES

Because Richard Hay was very interested in active loudspeakers, he joined the now long-forgotten Active Loudspeaker Standards Organisation, along with Linn, Meridian, Naim and the Acoustical Reproduction Company (ARC). This working group was set up to define standards for active speakers, to provide interoperability between brands. He wasted little time in splitting his receiver up into component pieces so that it could go active. First, the CPA602 power amplifier was launched to provide a power upgrade for the CTA252, with over 60W RMS per channel “and a sound to rival Naim”, in the words of Phil Balaam. This came out in 1979 and was soon joined by the CTP102 tuner/preamplifier, which was basically the CTA252 without power amplifiers. 

In early 1980, the EXO102/3 electronic crossover and CXA252 crossover amplifiers were launched. Owners of CTA252s and ARC or Linn speakers could add the CXA252 to convert their system to a fully active loudspeaker with the power amps in the CXA driving HF and LF for the left channel and the power amps in the CTA252 doing the same for the right. Balaam remembers that

The difference in musical quality was astounding, it was the best value upgrade available and made Nytech/ARC active systems highly desirable. The CPA602 power amp is the best thing Nytech ever did; it’s a wonderful sounding thing.

Richard Hay formed a strategic partnership with ARC. The 101, 202 and 050 speakers were all converted to run in active mode, with an easily removable passive crossover at the back. “It did a lot for ARC loudspeakers,” says Phil,

Because for a fairly small upgrade price you got a system that was in a completely different league. When the big ARC202 speaker came out in active form, a real war started, as people started to compare it favourably to the Linn/Naim Isobarik active system – whereas the Nytech CTP102 tuner preamp, EXO102/103 crossover, and two CPA602 power amps driving ARC202s, cost about a tenth of the price!

Nytech CTA252

Even by today’s standards, the CTA252XD II sounds excellent, with a warm, expansive and musical sound. It needs to be paired with an efficient pair of loudspeakers – I used Cambridge Audio AeroMax 60s – but this done you get a very nimble and expressive sound that’s far less processed than many modern amplifiers. Tonally it’s a bit softer and more rounded than many on the market today, and its fulsome, bouncy and fluid bass doesn’t quite have the grip of modern amplifiers. Yet still, the Nytech is lots of fun to listen to and has real finesse and detail too. Valve fans will love it; headbangers won’t. The tuner needs a proper aerial because it’s insensitive compared to modern radios, but this done it is wonderfully open and expressive. Indeed, it really is so good that it makes almost all modern tuners sound two-dimensional, thin and processed. 

AND IN THE END

Many audiophiles regard the Nytech CTA252 as one of hi-fi’s lost treasures, and one of the best kept secrets of a now-departed golden age. Some 30,000 examples were made until production was stopped in 1982 when the case moulds reached the end of their useful lives. It was probably for the best because the Nytech ‘calculator tuner amplifier’ really wasn’t ready for the brave new world of digital audio that was just around the corner. Today, however, it represents a brilliant second-hand buy because even quite decent examples routinely change hands for under £100. For a mint, boxed specimen, you’ll likely not need to pay even twice that. 

Nytech ceased trading in the early nineteen nineties, but the spirit survives with Heed, whose modern product range shares much of the original Nytronics/Nytech DNA. The Nytech Audio name lives on today in the capable hands of Phil Balaam. He takes care of the servicing and upgrading of all legacy products from his Cardiff workshop. As Richard Hay’s former right-hand man – during the golden age of the company from around 1974 until 1985 – no one else is better qualified to keep classic Nytechs going.

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David Price's avatar

David Price

David started his career in 1993 writing for Hi-Fi World and went on to edit the magazine for nearly a decade. He was then made Editor of Hi-Fi Choice and continued to freelance for it and Hi-Fi News until becoming StereoNET’s Editor-in-Chief.

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Tags: nytech audio 

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