Pioneer PD-T07

Commentary

This CD player was the first to adopt a unique turntable system based on the concept of no vibration and no resonance disc developed in the development of disc stabilizers.

In the CD turntable system, a pickup and a spindle motor are installed on the top of the disc to hold the entire disc from the bottom. Therefore, the disc is placed on the turntable with the pit surface facing upward. The disc rotates together with the turntable, and the pickup on the top of the disc reads the pit.
This mechanism is not only affected by external vibration and sound pressure, but also by the large inertia unique to the CD turntable mechanism, it is possible to suppress unnecessary vibration even when the rotational state changes due to a disc with a sled.
In addition, the moment of inertia of the turntable is approximately three times higher than that of the conventional one. It also works advantageously against torque ripple and cogging. Combined with the spindle motor with a starting torque of 65g ・ cm, it is robust against load fluctuations and provides highly stable drive performance.
As a result, the generation of jitter in the read signal due to vibration and surface blur is reduced by approximately 15%.

We have adopted an in-house developed Clean Laser Pickup.
By reducing the number of optical components such as collimator lenses, the power loss of the optical system is reduced, and aberrations in the optical path are also reduced, making it possible to read a clean and low-distortion pit signal.
In addition, it uses a photodetector with built-in I/V conversion head amplifier to amplify a weak signal of several μ A to the order of approximately 200 mV, enabling transmission that is less affected by disturbance noise.
A high-precision engineering plastic body is used for the pickup body. By dividing the pickup body into approximately 1000 elements and performing strength analysis, a high-precision and precise shape is realized.

The pickup drive is equipped with a silent linear motor servo mechanism with excellent response and low vibration.
In addition, in order to rotate the CD turntable with large inertia mass, the spindle motor is equipped with a large brushless hole motor with starting torque of 65g ・ cm. In addition, it is combined with an extra-thick shaft of φ 4.5 mm, so that the drive performance is strong against load fluctuations and stable against rotational speed fluctuations from the inner circumference to the outer circumference.

In order to obtain high-precision focus servo, the photodetector is divided into four parts. However, when receiving laser light, a phase difference occurs between the leading signal and the trailing Yukinobu signal, causing a disturbance in the synthesized RF-signal.
To solve this problem, we have adopted an Accu-Focus system. By delaying the preceding signal with a delay circuit to match the phase with the following signal, we can obtain an RF signal with less signal reading error.

The D/A converter uses an 8 fs digital filter and a left-right independent bit stream 1-bit DAC.
New Bit Stream The 1-bit DAC has only one electronic switch and one current source, and the analog quantity is expressed by the on/off of one electronic switch. This eliminates the problem of the error of the resistor and the difference of the operation timing unlike the multi-bit DAC. Therefore, it has excellent linearity and in principle, there is no non-linearity or 0 cross distortion.
In addition, while multi-bit DACs express analog signals in terms of vertical amplitude width (pulse height), 1-bit DACs express them in terms of horizontal time axis (coarse and dense waves of pulses), so it is called PDM (Pulse Density Modulation) method. In response to digital data input, pulses are generated at a high speed of tens of thousandths of a second, and analog signal waveforms are converted into coarse and dense waves of pulses.
In the 1-bit DAC, noise shaping is performed to reduce requantization noise caused by bit compression. In the PD-T07, over-sampling as high as 192 fs is performed at the pre-stage, and the signal is sent to the third order noise shaper to suppress the influence of out-of-band noise.
A system clock as low as 16.93 MHz is used as the system clock necessary to control all operations of the 1-bit DAC to suppress the effect of jitter.
Attention is also paid to the application, and an independent oscillation circuit is provided, and anti-vibration and anti-magnetic processing are applied.

Lamisert mechanical base is adopted to protect the optical mechanism from vibration from the outside.
This is made by molding two sheets of steel plate with special resin, and copper plating is applied to improve vibration damping characteristics and suppress the occurrence of magnetic strain.
This mechanical base is mounted on a mechanical chassis via a coaxial suspension with special rubber and springs, and the lower turntable base is also mounted via a coaxial suspension. The float structure prevents external vibration from the chassis.

Using direct construction, each circuit block is laid out simply and straight along the signal flow, and the shortest signal path is realized.
In addition, the digital / servo and audio circuit boards are separated to prevent mutual interference. In addition, a sealed PCB (double-sided circuit board) is used for the digital and analog circuit boards to provide an advantageous shielding effect against noise jumping from the digital to the analog circuit boards. In addition, the analog circuit boards are also connected at the shortest distance from the input terminal to the output terminal and have a symmetrical configuration.

The audio circuit after D/A conversion uses a class-A operation FET buffer amplifier. By reducing the output impedance, the influence of the load of the connected amplifier is reduced. In addition, by using class-A operation, fluctuations in power consumption during operation can be reduced, the influence on other circuits is reduced, and a low distortion factor is realized.

The power transformer is a twin power transformer for digital / servo circuits and analog circuits.
In addition, the transformer for the audio circuit has a bifilar winding, and by increasing the balance of output impedance and inductance, the + side and - side power supply are supplied under the same condition, contributing to sound quality improvement.
In addition, the four parts of servo / digital, servo drive, and audio + and - are independently rectified to eliminate mutual interference. In particular, the audio power supply uses a discrete push-pull power supply to provide a power supply with low output impedance and strong resistance to load fluctuations. In addition, the left and right independent power supplies are used for the DAC. The power supply for the servo drive is separated into one for the turntable and another for other drives. By stabilizing each power supply, the influence of motor and actuator operation is eliminated.

Newly developed multi-layer honeycomb chassis is used for the chassis.
This chassis is based on a honeycomb chassis made of BMC (Bulk Molding Compound), which has high internal loss and excellent vibration resistance and strength. Steel plates and cushioning materials with excellent electromagnetic shielding are layered to achieve high rigidity and excellent vibration resistance. In addition, the PD-T07 is plated with copper to reduce magnetostriction and improve vibration resistance.
In addition to the large honeycomb insulator that absorbs external vibration, a fifth insulator is installed in the center of the chassis to ensure vibration control and weight balance and support the center mechanism.

A cushion material with excellent damping properties is attached to the thick extruded aluminum bonnet to eliminate resonance.

The power cord is a 4-core cord that separates the core wire from the power plug for the servo system and analog system only.
In addition, it uses OFC (high-purity oxygen-free copper).

We use carefully selected items such as capacitors and resistors for audio.
In addition, the circuit boards and parts are shielded so that high frequency waves do not escape from them and affect other circuits. In addition to the full-face sealed servo board and the use of glass-epoxy double-sided boards for audio circuits, capacitors and wiring materials are also treated uniquely to prevent noise.

A balanced output terminal is provided so that it can be connected to an amplifier with a balanced input.

It is equipped with a clean microcomputer that operates only when the key is pressed, and it cancels weak scanning noise.
In addition, it is equipped with a display off switch that suppresses noise generation when lighting.

Equipped with a digital / anlogout changeover switch.

Model Rating

Type	CD Player
Pick-up	Three beam semiconductor laser system
Frequency characteristic	2 Hz to 20 kHz
Signal-to-noise ratio (EIAJ)	115 dB or more
Dynamic Range (EIAJ)	99 dB or more
Channel Separation (EIAJ)	110 dB or more
Wow & flutter (EIAJ)	Measurement limit (± 0.001% W. PEAK) or less
Harmonic distortion factor (EIAJ)	Not more than 0.0015%
Output voltage	2.0Vrms
Number of channels	2 channels (stereo)
Digital output	Coaxial Output : 0.5Vp-p/75 Ω Optical output : -15dBm ~ -20dBm (wavelength 660 nm)
Pwer	100 VAC, 50Hz/60Hz
Power consumption	22W
External dimensions	Width 420x Height 140x Depth 365 mm
Weight	11.5kg
Attachment	Remote control