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Vic Keary

Thermionic Culture Valve Designs
By Hugh Robjohns

Vic Keary in his workshop. A Culture Vulture can be seen on test on the workbench.Vic Keary in his workshop. A Culture Vulture can be seen on test on the workbench.

We talk to a British designer who still thinks audio is best served by tube.

Among audio engineers the arguments over the virtues and demerits of valves (or tubes) versus solid-state electronics are almost as ceaseless and polarised as those over analogue and digital recorders. However, for those who favour glowing glass bottles, one of the best-kept secrets of the British Isles has to be a quiet little company called Thermionic Culture. Although they currently only manufacture three products, all three are unusual, distinctive all-valve designs.

The designer behind these products is recording-industry veteran Vic Keary, who argues very coherently that every stage of the audio signal chain — amplification, compression, mixing and equalisation — all took a step backwards when solid-state technology became commonplace in the late 1960s. Consequently, none of his products have any transistors or ICs in their signal paths at all, and the few solid-state components that are used are restricted to serving in the power supplies — where they have distinct practical advantages.

Engineering Beginnings

Vic has a long and colourful history in the British recording scene dating back to the 1960s. He built his very first semi-professional recording studio in 1957 above a cow-shed — and 'built' is the right word. In those days you more or less had to build everything yourself, as there was very little in the way of commercially produced equipment. From this novel beginning, Vic's professional career began in 1960 as a maintenance engineer at Lansdowne Studios in London. Among his engineering successes at the studio was a significant modification to the EQ of the studio's EMI console — a design which has been carried over to Thermionic Culture's forthcoming Merlin EQ.

In the early '60s, Vic progressed up the ranks at Lansdowne to become a mixing engineer in his own right, crafting several hits by the Terry Lightfoot Jazz Band, among others. Possibly his best-known chart success from that era, though, was Acker Bilk's 'Stranger on the Shore', which he mastered.

After leaving Lansdowne in 1964, Vic worked with a company called Rush Electronics, and during his brief time there he designed some valve compressors derived — but very heavily modified — from an early Altec design. Vic's design had the unique feature of employing both a neon and a bulb illuminating a light-dependent resistor (LDR) as the gain-controlling element. Most opto-compressors have fairly slow attack times because of the relatively slow light build-up of an incandescent bulb, but in Vic's design, the neon bestowed the compressor with a fast attack time, while the bulb controlled the release time. One of these unique compressors was sold to Pete Townsend, and he apparently still uses it today (allegedly with the original valves!). Elements of that revised design later went on to form the heart of the Chiswick Reach compressor, which Vic designed, and more recently Thermionic Culture's Phoenix.

Vic couldn't stay away from the recording business for long, and soon left Rush Electronics to set up a London-based three-track recording studio, Maximum Sound. Vic built the studio's 10-channel console himself, based on the design of the EMI console at Lansdowne, and expanded the studio to four-track over the years. Eventually, the studio acquired quite a reputation for recording successful ska and reggae music.

Vic continued this success at his next venture, Chalk Farm Studios, which he founded in 1968 following the sale of Maximum Sound to Manfred Mann. He reinstalled his valve desk along with an eight-track Leevers Rich recorder, and some of his compressors. Reggae and soul success soon followed — at one time, eight of the top 50 singles had been recorded at Chalk Farm, Vic having mixed five or six of them! Dandy Livingston (then Trojan's chief producer) made many of his records at the studios, and Harry J produced Bob and Marcia's single 'Young, Gifted and Black' — the studio's first hit — even though the equipment was pretty basic by today's standards. Vic recalls today that the outboard comprised a single spring reverb, and that the unique delay on the strings on that record was achieved by mixing outputs from both the sync and replay heads on the eight-track!

The studio gradually expanded to a 16-track facility (and later to 24-track), outgrowing the original console, so Vic built a larger 20-channel version with a separate monitor mixer, which was better suited to multitrack working. Sadly though, as the popularity of reggae diminished at the turn of the '80s, so too did the studio bookings, and Vic was forced to close the studio in 1982. For the rest of the decade he scratched a living from freelance studio maintenance, vinyl disc mastering and occasional location recordings.

Thermionic Culture's co-founder Jon Bailes.Thermionic Culture's co-founder Jon Bailes.Vic was drawn back into the recording studio world at the beginning of 1990 after the private studio of an acquaintance was burgled and stripped of all its equipment. He agreed to install some of his own gear to get the place up and running again, and the large proportion of valve outboard quickly became the highlight of the facility. Many customers suggested setting up an all-valve studio, so Vic did just that in 1992 at a converted brewery near the river Thames in Chiswick, West London, naming it Chiswick Reach, and was joined there the following year by Nick Terry, a valve-obsessed recording engineer. The studio used Vic's (by then) 28-input, eight-buss, 16-monitor channel valve console from the Chalk Farm days, together with his impressive collection of valve outboard equipment. This included Leevers Rich graphic EQs, an EMT plate, and a Sean Davies valve limiter (made in the 1960s for IBC Studios, where it was apparently used on The Who's 'My Generation'). Tape recorders included a 3M M79 24-track and a Brenell Mini 8 (both dating from the 1970s), as well as a Leevers Rich E242 two-track valve recorder, which Vic still owns!

Vic left Chiswick Reach in 1998, but continued to design and build valve audio equipment for friends and colleagues, and this led to the idea of manufacturing his designs commercially. To this end, Thermionic Culture was founded in 1999 by Vic and Jon Bailes, a designer in the electronic manufacturing industry. While Vic develops the circuit designs, Jon is responsible for the mechanical design, visual appearance and production engineering of the products.

Nick Terry stayed at Chiswick Reach for a few more years honing his skills, before leaving to work as a freelance engineer/producer on projects such as McAlmont & Butler and The Libertines, and has now become the third partner in Thermionic Culture. Nick is responsible for the testing and quality-control side of things, and also provides a lot of the ideas for new or improved products. He often uses Thermionic Culture products on his recording projects — including some prototypes — and this helps him to evaluate the designs and provide real-world feedback for their development.

Product Designs

Some of the Thermionic Culture circuit topologies and concepts can be traced back to the classic valve designs from the 1940s, but a lot of the detailed designs involve Vic's own innovative work. Regardless of the source of inspiration, all of the valve circuitry has been revised and optimised to achieve the performance, low noise levels and minimal distortion expected of modern recording equipment. High-spec components are used throughout, including one-percent metal-oxide resistors and polypropylene capacitors where they influence the sound quality and reliability. Valves are selected by hand (and matched where necessary), usually from military or industrial types to ensure the longest possible life and accuracy. Many are rather unusual models not normally seen in audio applications, but are employed where they bring worthwhile benefits to noise, distortion or reliability.

Some of the company's products retain the point-to-point wiring which is traditional in valve equipment, but while this approach can have certain technical advantages, it also makes production slow and expensive. The intention for the newer designs is to start using Jon Bailes' expertise in designing printed circuit boards, and although these can take a long time to optimise, production is quicker and more cost-effective — which should translate into more affordable products.

The Phoenix compressor.The Phoenix compressor.

The Phoenix was the first of Thermionic Culture's products, and its design derives in part from the Altec 436 'vari-mu' compressor. This used 6BC8 triodes in a balanced (push-pull) configuration, but produced what Vic felt was unacceptably high distortion, so he improved the design during his time at Chiswick Reach, and it became known as the Chiswick Reach compressor (reviewed in SOS February 2000). However, the noise floor was still not as low as Vic wanted, and further development eventually resulted in Thermionic Culture's Phoenix compressor. Some of the noise-floor improvement came from changes to the power supply, but some also came from a redesigned front-end which used a PCC85 valve instead of the Chiswick Reach's 6BQ7A. The PCC85 tube was designed for FM radio applications and hasn't been used in an audio application before; it requires an unusual 9V heater supply. However, all these cumulative changes brought the overall noise figure below -100dB, improved distortion further to 0.1 percent, and enhanced the general reliability of the compressor. Vic also improved the machine's flexibility and performance over the Chiswick Reach design with faster attack and release times. As this history shows, Vic is an inveterate tweaker, and still feels there are advances to be made with valve technology. He is currently experimenting with a different output valve for the Phoenix.

The Phoenix's 'vari-mu' label means it has a very gentle 'knee' (in other words, the compression ratio increases gradually around the threshold), producing a very subtle, transparent compression effect. This makes it ideal for enhancing vocals and solo instruments, adding both warmth and body as well as making the source more powerful — all in an unobtrusive way. It also serves well as an overall mix compressor. Apparently, over a hundred have now been sold.

Engineer Nick Terry testing an Early Bird 2 mic preamp in the quality-control department.Engineer Nick Terry testing an Early Bird 2 mic preamp in the quality-control department.The Culture Vulture was Nick Terry's idea, and is essentially a distortion processor for adding creative dirt to individual instruments or complete mixes. The large rackmount unit, which is available in mono or stereo versions, provides triode or pentode distortion (mainly even and odd harmonics respectively), with the option of including some first-stage feedback to create a distortion character somewhere between the two. In this way, the Culture Vulture can generate a wide range of different and distinctive distortion effects, recreating the recognisable characteristics of different valve amp topologies (for more information, see the SOS review).

Given that the raison d'être of this unit is to generate distortion, the specs make entertaining reading! Base distortion is quoted as 0.2 percent, but at full stretch the unit produces a staggering 99.9 percent distortion.

The company's third product is the Early Bird mic preamp. This was originally introduced three years ago, but it has now been redesigned by Vic. The new version — the Early Bird 2 — includes simple EQ facilities, with a high-pass filter, bottom lift, a broad mid-range control, and a top lift. The EQ is within a feedback circuit and the way it has been designed means that the filter slopes vary with gain settings. In particular, the high-pass filter has a 12dB-per-octave slope at low-frequency settings, but it softens considerably at higher settings, providing a gentle mid-cut when combined with the bass lift control.

The circuitry is again based on a unique push-pull balanced design, but the basic topology is similar to an amplifier design employed in a Pultec equaliser. Unlike the other products, the Early Bird 2 uses fairly conventional valves throughout — ECC83s and ECC82s. Sowter transformers are used throughout Thermionic Culture's products — both for audio and mains — and in the case of the Early Bird 2, the input transformer offers dual impedance settings of 300 and 1200 Ohms, allowing both vintage and modern mics to be matched to the input.

It requires a good solid-state preamp to deliver a signal-to-noise ratio of more than 100dB, but that's also what this all-valve design can achieve — combined with distortion below 0.005 percent, and an extended bandwidth to 80kHz (all at 44dB gain). These specs are certainly impressive, regardless of the fact that it is an all-valve design, and the sound is even more so. It has a very clean, slightly warm but open and airy sound quality — and the extended frequency response and very low phase shift make it a popular choice for both high-quality classical and rock recording duties.

The Future

Several new Thermionic Culture products are currently at the planning stages. The Merlin, for example, is a versatile equaliser with an interesting 'passive lift' feature. Also in the wings, with a launch provisionally scheduled for the end of the year, is the Nightingale — a valve recording channel with a mic preamp, simple EQ and a scaled-down version of the Phoenix compressor. But with Vic's history of console design — and the enormous commercial success of the studios equipped with his early consoles — an all-valve console seems an obvious gap in the product line-up. In response to this, Vic has told me that he and his partners are considering producing a Thermionic Culture console, but they are still deciding the exact form it should take. Clearly the market for such a desk would be relatively small and the cost relatively high, so getting the right facilities in the package is paramount. In my view, though, an all-valve console incorporating Vic's mic preamp, compressor and EQ circuits is worth waiting for. Watch this space...

Published June 2004