Sony Biotracer turntables.
The Sony PS-X75 Biotracer turntable.
“Biotracer” was the name Sony gave to it’s range of record decks produced from 1978-1984.
The first commercially produced model was the PS-B80, an absolute technical tour de force, expensive and now rare. It featured a very high torque direct drive motor, a heavy chassis with an SBMC non-resonant base, and a self-balancing Biotracer arm. There was no user adjustable arm counterweight. A zero balancing function was automatically performed electro-magnetically every time the arm returned to it's rest. As on the later Biotracer decks, tracking weight was applied by means of a small dial on the control panel, again electro-magnetically.
Following on the heels of the PS-B80 was the PS-X75 (gallery at the top of the page) and the PS-X700. There is a feature of the Sony PS-X75 Biotracer on this website. Basically this was an internally simplified version of the PS-B80 and consequently cheaper to produce. The auto-balancing feature of the PS-B80 was ditched in favour of a conventional counter-balance arrangement, housed in the rear casing of the arm. The compact PS-X500, X555, X600, X800, followed, still more economical to produce, but reasonably effective nonetheless.
Early Biotracer designs were expensive and marketed primarily for the audio connoisseur. Despite their internal complexity, they were easy to set up and even easier to use. Little or no adjustment was needed after the initial installation. It was almost plug in and play audio bliss, with truly consistent and predictable results. How different to the fickle, bouncy, suspended efforts which needed so much setting-up and so revered in the UK at the time.
All Biotracer turntables had quartz locked, direct drive motors. However, the particularly interesting common feature was the tone arm - a feat of engineering, innovative and highly effective as a pick-up cartridge carrier. The object of the exercise was to reduce/eliminate arm resonance electronically, as opposed to the mechanical damping methods employed by other arm manufacturers, and currently universally employed. The Biotracer arm movements were entirely controlled by coils (motors). Other coils within the arm were used to detect vibrations caused by unwanted resonances. If such vibrations occurred, an electrical signal was generated by the coils, sent to a feedback circuit and an opposing force applied to the arm electronically to counteract the unwanted motion. This had the effect of controlling low frequency resonance to a great degree, with consequent associated benefits throughout the frequency spectrum, including providing extraordinary stereo separation.
All the Sony Biotracer models could assess the size of disc, utilizing photo cells beneath the platter to detect light passing through slits on the platter surface. Certain light slits were blocked by a 7 inch single, whilst all the slits were blocked by a 12 inch LP enabling the deck to detect the size of the record to be played. If there was no disc on the platter, the arm would not lower but return to its resting point. The decks were fully automatic with a well damped lift/lower system to handle even the most delicate cartridges. On the PS-B80, arm raising and lowering didn’t involve a mechanical system at all - it was all implemented by coils and electro-magnets. You may think it likely that all this automation would constitute the perfect recipe for a sonic disaster, but as there was never a direct mechanical linkage to the arm , this was not the case.
The PS-X555 and PS-X800 utilized tangential tracking arms, in Biotracer mode. This allowed for an even greater reduction in tracking distortion. The “end of side” distortion with all Biotracer arms is minimal in any case, with superb image stability, depth and channel separation during the most taxing passages. The vertical tracking angle (VTA) is not adjustable on the later models (PS-X500, PS-X555, PS-X600, PS-X800) . Spacer washers can be added to the headshell to alter the VTA, but of course only if the arm is sloping downwards from the rear. I have used spacers successfully in a PS-X 600, with a high-compliance Ortofon cartridge.
Was the Biotracer system effective? The short answer is yes, in fact spectacularly so. It's very difficult to categorize the sound of these decks relative to other offerings, but the characteristic sound is much more akin to that of a CD, than a record. Nevertheless, the smoothness and musicality so revered by enthusiasts of analogue is retained. Cartridges invariably sound very “fast”, lively, stable and clean. As mentioned earlier, stereo separation is exemplary.
I have used several high-end cartridges on a PS-X75, and without fail, they all out-perform in the Biotracer arm when compared to a conventional pivoted arm. This is both in terms of sound quality and an ability to track the most demanding pressings. It's quite uncanny.
These photos show the underside of a PS-X75. Clearly visible are the massive coil assemblies beneath the arm bearing, responsible for the arm movement. Four of the fine wires are signal wires, but others are routed to the arm tube and connected to the small sensing coils at the rear of the arm tube.
So why aren't Biotracer arms regarded now universally regarded as analogue Nirvana? Apart from prejudice against anything not in the mainstream, or simply not knowing about them, it’s understandable if prospective purchasers are wary of the electronics and mechanical intricacies involved. These decks are complicated, but they are serviceable by a very competent electronics engineer, and the impossible to find microchips rarely fail. I have had my own decks serviced serviced and checked, as after 30 years it’s possible that electronic alignment is likely to drift. The electronics have been re-calibrated (by pots on the circuit boards) in accordance with the Sony service manual. The manuals are readily available on the excellent Vinyl Engine website. If you own one of these decks which require servicing and are in the UK, feel free to contact me and I will put you in touch with an expert engineer.
With regard to the PS-X75 and PS-X700, there is no upper limit as to the quality of cartridge that can be fitted to these decks. I have used Sugano era Koetsu's and a Kondo IO-M to great effect. Dynavector moving-coil cartridges have also proved a very good match. My preference is to use cartridges of low to medium compliance in the early Biotracer models, but the arm seems to perform fine with high compliance cartridges too, as the way the arm works seems to throw conventional thinking overboard.
Make no mistake, these decks were not some pointless foray into the use of the then innovative, micro-processor technology. Arm manufacturers nowadays simply do not have the resources or inclination to investigate the original Biotracer approach, which yielded such good results. It’s much easier, cheaper and more profitable to continue producing relatively crude variations of metal rods which rely on mechanical design for resonance reduction, no matter how effective an alternative approach was in the past. Interestingly, isn't this the case with turntable drives too. Why on Earth would you favour a crude, mechanical, rubber belt drive over an elegant, no-maintenance, quartz-locked direct-drive option? I suggest for the same reasons as before.