Sony Biotracer arm. The rear housing contains the counterweight to balance the arm to zero and the sensor coils for vertical movement

Click on the image for more detail.

In the foreground is the coil and magnetic assembly. Whilst the desired tracking pressure is applied electronically, "zero weight" is achieved with a conventional counterweight at the rear of the arm. The large thumbscrew at the very rear moves the square counterbalance weight back and forth.

The Sony PS-X75 is a 2-speed, direct-drive turntable equipped with the Biotracer electronically controlled tone arm. The deck is of substantial construction and features a plinth constructed of SBMC, a proprietary anti-resonance compound manufactured by Sony.

The horizontal and vertical movements of the Biotracer arm are constantly monitored by sensors within the arm and plinth, and this information is passed to a “feedback” system which counteracts and suppresses unwanted arm vibration. The vertical arm movements are controlled and accomplished by components within the top housing of the arm itself, whilst the coils and magnets which deal with horizontal movements are located within the plinth.

Basically, the Biotracer feedback system has the effect of damping tonearm movement not associated with traversing the record during play. This is not unlike the Townshend "Rock" turntable, but in this case it is accomplished electronically, without the need of a silicone fluid trough. This damping effect helps obtain the maximum signal to noise ratio, significantly improving tracking ability and stereo separation. This results in an extremely stable stereo image usually only associated with the very best and expensive vinyl players.  

Unlike the PS-B80, the arm is balanced to zero weight manually with a conventional counterweight, though this is hidden in the housing at the rear of the tonearm. The required downward stylus force is applied electronically by adjusting a control on the front panel. This can be altered whilst the record is playing. The required anti-skating (bias) force is automatically applied to correspond with the stylus force setting.

Record size is detected by a photo sensor system.  If no record is on the platter, the tone arm will not descend but will return to it's rest.  An optical sensor detects a record's lead-in and return points, and the linear motor guides the tone arm to the precise position. There is no mechanical linkage from the turntable drive to the arm as in traditional semi-automatic units.

The Sony PS-X75 maintains accurate and drift-free speed by referring to a frequency generated by a very stable crystal oscillator. In addition there is a speed monitoring system which utilizes a magnetic pick-up head and a pulse signal derived from a magnetic coating at the inside edge of the platter.The platter reaches the correct speed within half a rotation and an electronic brake system stops the turntable quickly and smoothly.

The Sony PS-X75 is one of classic audio's gems, and don't be fooled by the modest exterior. Largely owing to the arm design, the PS-X75 can provide sound quality to match that the very best turntables currently available, and is best suited to high calibre cartridges. That the deck was manufactured with very early 80’s technology is entirely immaterial.

The Sony PS-X75 is very easy to set up and, in the normal course of events, requires no ongoing maintenance or re-aligning at regular intervals as suspended chassis designs do. If a PS-X75 is not performing as it should, ensure a qualified and knowledgeable engineer undertakes any remedial work as the electronics are plentiful and complicated. If you are resident in the UK, I am happy to assist with recommending an excellent engineer.

A service manual is available free on the excellent Vinyl Engine website.

 The dark magnetic coating on the inside of the platter should not be damaged.

The dark magnetic coating on the inside of the platter should not be damaged.

If you are thinking of purchasing a PS-X75, there are a few points worth bearing in mind:

  • Ensure that the magnetic coating on the inside edge of the platter is not scratched or damaged. If it is, there is the strong possibility that the turntable will not rotate at the correct speed, as the pick-up head will not be able to "read" the strip properly. This is not repairable.

 

 The additional counterweight to allow use use of cartridges above 8 grams in weight.

The additional counterweight to allow use use of cartridges above 8 grams in weight.

  • The Sony PS-X75 was originally supplied with an additional tonearm counterweight which could be attached to the rear of the arm. This allowed for heavier cartridges which weighed over 8 grams to be counterbalanced. If the weight is missing, you may be restricted to using lighter-weight, magnetic cartridges.

 

  • In my opinion, the weak spot of the Sony PS-X75 is poor isolation from external vibration. The SBMC base helps in this respect as does the gel mounting for the deck feet, but the unit benefits greatly from being used on a substantial, stable base or stand. Alternatively, a very solid wall shelf or a "floating" platform is ideal too.

I have written an article featuring the Sony Biotracer turntables with an accompanying video for the PS-B80 Biotracer. The sonic performance of the PS-B80 and PS-X75 is very similar but with the former having even more of a "clinical" delivery than the PS-X75.

Sony PS-X75 Biotracer turntable specifications.

 

Motor: Linear BSL motor
Drive system: Direct drive. High torque motor. Full speed within half a revolution.

Platter: 32cm alloy die-cast aluminium
Control system: Crystal lock control, magnedisc servo control system.
Speeds: 33.33 and 45rpm
Wow and flutter: 0.015% wrms
Signal to noise ratio: 78dB
Tonearm: Universal electronic, "J"- shaped.
Effective length: 235mm
Overhang: 13mm
Tracking force range: 0-3 grams.


Original cartridge headshell weight: 11 grams.
Cartridge weight requirements:  1-15 grams. Cartridges over  8 grams must use the the extra counterweight supplied with the turntable by Sony.

Dimensions: 480 x 165 x 420mm
Weight: 13kg.