DESCRIPTION :

Driving System

1. Crystal Oscillator

Reference clock oscillator that provides a clock signal to stabilize rotation frequencies for the motor.

2. Direct Digital Synthesizer (DDS)

This functions as a synthesizer to divide the input clock signal according to the values of frequencies determined by the microprocessor, converting high frequencies to low frequencies so that they will work with the motor. Almost any value of frequencies can be output and precise control of the rotation is possible.

3. Torque Switching Circuit

This circuit switches the voltage to the motor in order to quickly increase the rotation torque to a rated speed during a startup or when shifting the rotational speed of the platter. When a rated speed is achieved and the rotation speed is locked, the torque will then be decreased in order to reduce vibrations even further.

4. 3-phase Signal Generator Circuit

This circuit creates an accurate phase shift to the input signal of 120 degrees to generate 3-phase AC output for the 3-phase motor.

5. Motor Driving Amplifiers

There are three 150W power amplifiers for the respective three phases, with ample current to optimally drive the synchronous motor.

6. Synchronous Motor

The motor is a 3 phase AC motor operating in synchronization with an accurate 3 phase frequency, generated with the 3 phase signal generator circuit. A more common power system for the motors has AC power phase shifted with capacitors. In the latter case, it is very difficult to provide an AC signal output with accurate phase shift due to ageing and errors in the capacitors etc. Such issues can lead to a decrease in torque and an increase in vibration.

7. Sensor

This detects the speed of the platter and transmits the information to the microprocessor.

8. Microprocessor

This controls the motor driving mechanism so that an extremely high precision rotation will be achieved.

Control Mechanism for Motor Rotation

By using a specific rotation speed for the motor stored in advance, the DDS sets a corresponding frequency value and the motor performs a high torque rotation at this stage. The microprocessor computes the difference between the rotating speed detected by the sensor and the target speed.It then transmits a speed control signal to the DDS, which in turn controls the rotation to achieve the target speed.

The indication of “LOCK” blinks on the display during this process. Once an accurate rotation of the platter is reached, “LOCK” displays permanently on the display. At the same time, the microprocessor sends a command to apply low torque and deactivate the DDS while monitoring the rotation. This is because not much extra force beyond inertia is required for a steady rotation. If the rotation speed is changed for any reason, “LOCK” will blink on the display and the microprocessor will use the DDS to correct the speed. Once the accurate speed is achieved, “LOCK” will display permanently on the display and the rotation is kept in a stead state without the need to control the speed.

The Platters & Chassis design

Platter Base

The Platter Base (35 kg, extra super duralumin) serves as a hub for the air suspension system. This Platter Base has four massive blocks composing the air suspension system mounted on it, and where two tonearms can be fitted. The Platters are made of different alloys and placed on the Platter Base. The air suspension system successfully eliminates vibrations that could transmit from the Platter Base to the tonearm and record surface by having the center of gravity much lower than the supporting point. This concept was key to our design, opposed to a theory that weight acts solely as a barometer to record players as some people believe.

Base Frame

The Platter Base sits on a 100 kg Base Frame made of SUS stainless steel. This Base Frame, which has an enhanced speed of oscillatory convergence with special surface treatment, supports the total weight of 230kg of the Platters, Air Suspension System and Platter Base.

Tonearm Bases

Two titanium tonearm bases are provided. Almost any 9 inch, 10 inch or 12 inch tonearms can be fitted with the exception of non-standard lengths.

Platters

The Platters are designed for the highest level of vibration absorption by combining different alloys. For example, the top layer is made of titanium with surface hardening treatment applied  to produce hardness equivalent to hard metal alloy. More importantly, these five layers of platters are held as one with air suction similar to vacuum LP hold-down. This solution allows to us to avoid metal fittings which could induce mechanical stress.

Air Bearing

The five platters float to the height of 10µm and rotate in absolute silence as one unit. To make this possible, the Platter Base surface is precision machined with a tolerance of less than Sµm at its circumference.

Air Suspension System

The AF Zero has an Air Suspension System consisting of four blocks providing insulation and absorbing low frequency vibrations at the four corners. This air suspension module is uniquely developed by TechDAS and air is supplied from an electric pump to the air suspension modules.