SONY TA-AX8

Commentary

A pre-main amplifier that pursues simple and straight transmission and introduces the new idea of the current drive.

An audio current transfer method is used to eliminate interference between the preamplifier and the power amplifier.
This circuit converts the signal applied to the preamplifier into a constant-current signal system using a current conversion amplifier, and loads the 2-terminal linear gain controller at the first stage of the power amplifier. Therefore, the preamplifier as seen from the power amplifier has infinite impedance, which is biogenetically equivalent to being completely disconnected.
As a result, four separate amplifiers with independent pre-amplifiers and power amplifiers for each left and right channel have been realized. This makes it possible to pursue independent characteristics and at the same time to provide ideal grounding, effectively improving performance. The input signal and load are fixed so that the effects of the earth loop and power source impedance, and the effects of wires and switches in the signal path can be ignored.
In addition, the two terminal gain control reduces the impedance as the gain is lowered, making the acoustic characteristics more effective. In addition, the power supply section of the preamplifier uses a constant current shunt regulator to isolate the influence of the power amplifier power supply, and the source impedance becomes almost 0, ensuring stable regulation.

A legato linear system has been adopted in which switching distortion and crossover distortion of the power stage are drastically reduced without using methods such as shifting bias or changing the power supply voltage.
In principle, the high-speed output Hi-ft transistor is operated in the minimum cutoff region. There are no nonlinear elements added to the signal system, and the operating condition does not change depending on the magnitude of the input signal. In addition, switching distortion is not observed up to the ultra-high frequency band of 100 kHz, and stable operation including phase characteristics can be ensured, so high-speed wide-band characteristics can be achieved.
The power amplifier of the TA-AX8 is a clean switching DC amplifier using this legato linear system.

In order to carry out the shortest distance wiring along the signal flow, it has been designed with the introduction of heat pipes applying heat treatment technology of spacecraft and electronic remote control of speaker switching.

As a measure against the temperature of power amplifiers, a heat pipe with thermal conductivity several hundred times that of a copper rod is used as a thermal conductor, which releases the transistor from the heat sink and eliminates lead wiring by attaching it directly to the circuit board.

The power supply section uses a pulse power supply that guarantees extremely stable regulation despite its small size.
In addition, since AC100V is turned into DC as soon as it enters the amplifier, 50Hz/60Hz AC magnetic field is basically not generated, contributing to the non-flux of the amplifier.

The power transistor is a Hi-ft transistor.
This transistor has a structure in which low-power transistors with good high-frequency characteristics are integrated in an infinite Daigo, and the operating range is widened from 60 MHz to 80 MHz from the conventional 4 MHz, and the high-frequency response is extremely high-speed, thus reducing TIM distortion that pollutes sound.

It is equipped with an FET differential servo equalizer amplifier without input / output capacitors. It is equipped with a fully connected DC amplifier without any capacitors from the signal system from the Phono input to the speaker output. This eliminates the low-frequency phase region.

High-quality parts such as high-speed rectifier diodes and large-capacity green capacitors are used.

Magnetic materials that affect sound quality such as non-magnetic aluminum top plate are eliminated as much as possible.

Equipped with a two stage protection circuit that uses both a power limiter and current detection.

It uses a soft-touch input selector with a relay that emphasizes sound quality.
The selected position is confirmed by the indicator lamp.

Equipped with a Rec out selector that allows you to select a recording source independently of the source being played.

Equipped with MM/MC cartridge load selector, capacity 100pF/180pF/330pF can be selected with independent knob in addition to 100k Ω / 50k Ω for MM and 40 Ω / 3 Ω for MC.

The sound quality is adjusted by using a smooth linear gain controller.

Equipped with tone control.
It also has a TONE/DIRECT ON switching function that can pass through the TONE circuit.

Equipped with a base boost function.

It is equipped with a speaker selector with relay.

Model Rating

Type	Pre-main amplifier
Effective power	100W + 100W (20 Hz to 20 kHz, both channel operation, 0.004% harmonic distortion rate, 8 Ω load)
Output bandwidth	5 Hz to 100 kHz (40W output, 0.02% harmonic distortion, IHF)
Damping factor	150 (1 kHz, 8 Ω)
Harmonic distortion factor (20 Hz to 20 kHz)	0.004% (at effective output) 0.003% at 50W output
Cross modulation distortion factor (60Hz:7kHz=4:1)	0.004% (at effective output) 0.003% at 50W output
Slew rate	250 V / μ sec 520 V / μ sec (inside)
Rise time	0.3 μ sec
Separation	Phono MC:70dB Phono MM:85dB Tuner/Aux/Tape:95dB
Frequency characteristic	Phono MM : RIAA curve ± 0.2 dB Tuner/Aux/Tape1, 2 : 0.1 Hz to 600 kHz + 0 -3dB
Input Sensitivity / Impedance	Phono MM : 2.5mV/50k Ω, 100k Ω / 100 pF, 180 pF, 330 pF Phono MC (40 Ω) : 130 μ V/100 Ω Phono MC (3 Ω) : 130 μ V/30 Ω Tuner/Aux/Tape1, 2 : 150mV/50k Ω
Phono maximum allowable input (Harmonic distortion factor 0.003%)	MM:310mV MC:15mV
Signal-to-noise ratio	Phono MM:84dB Phono MC:70dB Tuner/Aux/Tape1, 2 : 85 dB
Output Level / Impedance	Rec out1, 2 : 150mV/220 Ω Speaker A, B : 4 ~ 16 Ω (Simultaneous operation of A and B : 8 ~ 16 Ω) Headphones : 8 Ω or more
Tone control	Bass : ± 10 dB (60 Hz, turnover frequency 300 Hz) Treble : ± 10 dB (25 kHz, 5 kHz turnover frequency)
Base boost	+4dB(50Hz)
Low filter	15 Hz or less, 6dB/oct.
Muting	-20dB
Power consumption	190W
External dimensions	Width 430x Height 105x Depth 350 mm
Weight	Approx. 7 kg