Audio Database
Commentary

This monaural power amplifier was developed with the latest technology and devices aiming at the highest performance and sound quality as a power amplifier to reproduce high-quality sources with a large dynamic range more faithfully, which was born with the appearance of PCM equipment.

A high-voltage double-diffused MOS-FET is used for the power element.
The V-FET used in Sony amplifiers had greatly improved basic performance such as distortion factor compared with transistors. However, the negative bias of the V-FET makes it difficult to use in applications. For example, in the TA-N7, a measure was taken to improve this. For example, a cascode connection with a transistor with superior high-frequency characteristics was used. The power MOS-FET (2SK173/2SJ54) used in the TA-N9 was developed by further expanding and developing the high-withstand voltage technology of 1000 V and the power FET manufacturing technology obtained at the time of trial manufacture of the V-FET. Among MOS-FETs, it has a double-diffused structure that is considered advantageous for high-frequency characteristics and high-withstand voltage.
When a power amplifier is composed of this power MOS-FET, a large output can be easily obtained because it can handle a large current (up to 10A) at a high withstand voltage (210 v). In addition, it has high reliability and safety, and because it has excellent high-frequency naked characteristics, there is little transient intermodulation distortion.
The TA-N9 uses this element for the output stage in 5-pair parallel push-pull operation.

The circuit configuration of the amplifier section consists of a DC differential amplifier circuit with dual FET for the first stage and current mirror load. The second stage consists of a DC amplifier with an active amplifier. The voltage amplifier stage has a bare gain of approximately 100 dB. Moreover, since the bare characteristics before applying NF are improved, the distortion in the NF loop is also greatly reduced. The power driver stage is driven by a small transistor with excellent high-frequency characteristics because the input impedance of the power MOS-FET is large.
The complete DC amplifier configuration eliminates the problem of phase rotation in the low frequency range.

We have developed and adopted a heat pipe for audio equipment for the heat radiation part.
Since the TA-N9 has a large output, the maximum signal voltage is ± 90 V and the instantaneous current is 16A. This can affect the output stage to the first stage of the power amplifier. In particular, when the wire of the power element of the output stage is routed, the half-cycle signal of the SEPP circuit in Class B operation jumps out as electromagnetic wave and enters the first stage circuit, causing distortion of sound.
To solve this problem, a heat pipe is used. A special liquid is enclosed in a copper pipe, and heat is transferred instantaneously from one end of the pipe to another by continuously vaporizing and liquefying the liquid. This heat pipe has a thermal conductivity several hundred times that of a metal rod of the same diameter of copper or silver, and the conduction speed is close to the speed of sound. In addition, there is almost no temperature difference between stores, so efficient heat radiation is possible.
The power MOS-power MOS-FET of the final stage element can be concentrated and mounted on a printed circuit board, and heat is instantaneously guided to the heat radiation fins. In addition, aluminum shielding materials and shielding pipes are used for the input system to minimize the influence of electromagnetic waves.

TA-N9 can switch between class A operation and class B operation.
Since there is essentially no switching distortion during class A operation, more beautiful sound quality and low distortion are possible. In addition, since class A / B switching system with equal amplifier gain is used, you can enjoy the difference between class A and class B sound while listening.

A Pulse Locked Power Supply is used for the power supply.
The operation principle of the pulse-locked power supply is as follows : First, 100 VAC is directly rectified, then this DC is converted into a 20 kHz pulse, transformed by a high-frequency transformer, and rectified again to obtain the power supply voltage of the amplifier. In addition, in order to suppress voltage fluctuations caused by changes in the output signal of the amplifier section, a constant voltage circuit using a chopper method is inserted to convert the fluctuations into pulse width and control them.
In this system, the signal system is almost in a DC state just by rectification, so that the signal system is not interfered by noise caused by the power supply such as hum. In addition, as long as the capacity of the transformer is basically the same, transmission efficiency is better at higher frequencies than at lower frequencies. However, the pulse lock power supply is set at a high frequency of 20 kHz and uses a ferrite core with less high-frequency loss, thereby realizing higher efficiency than conventional power supplies using large toroidal transformers.
In addition, since the voltage is controlled to be constant by the pulse width control circuit, there is almost no voltage fluctuation up to the rated output of 0 to 450W. This suppresses the displacement of the amplifier stage due to the fluctuation of the power supply voltage, and the saturation is extremely small even at high power.
Since the pulse lock power supply directly rectifies the AC input power supply, the power supply frequency is not limited. Also, it can be operated with DC input (DC110V ~ 140 V). In addition, since it has extremely constant voltage characteristics, it has no effect even if the AC power supply fluctuates from 90 V ~ 130 V.
The TA-N9 uses a large-capacity pulse-locked power supply and a two voltage Minamoto no Sadamu system with a pulse-width constant voltage circuit inserted into each of the two positive and negative systems to reduce the fluctuation of the mid-point voltage. In addition, a four terminal capacitor is used to reduce the impedance rise at high frequencies. The TA-N9 achieves low output impedance characteristics from the DC range to the audio range.

The pulse lock power supply used in the TA-N9 has a sealed structure with strict electromagnetic shielding to prevent electromagnetic waves from affecting the amplifier circuit. The power supply consists of eight transistors for oscillation and eight transistors for regulator, which generate a large amount of heat. To cope with this situation, the power supply is mounted on a heat pipe.
A cylindrical high-frequency transformer with ferrite core with low high-frequency loss is used for pulse oscillation and electromagnetic conversion to improve efficiency. The coil of this transformer is also made of copper belt-like material to reduce impedance.

In order to achieve high reliability, a forced air cooling system using a DC motor is adopted.
This motor uses a linear BSL (slotless) motor with extremely low mechanical and electrical noise, reducing heat generation and rotational noise of the motor itself, and improving reliability.

As a protection circuit, a circuit with temperature detection, DC detection, and impedance detection is adopted.

Equipped with 6 point peak power indicator with LED.
This indicator is not intended to continuously monitor the output level, but rather to check the clip of the power amplifier or the power supplied to the speakers.
Since the peak power is required to be accurate, the attack time is 30 μ sec to improve the response characteristics. Generally, 1/10 of the peak level is said to be the average level. For example, when the 500W point of the indicator lights occasionally on an 8 Ω speaker, approximately 50W of power is supplied to the speaker.

Equipped with a 2-dB-step level attenuator that combines a resistor and a rotary switch.
The input level can be easily set. Moreover, the step type prevents inadvertent movement in case of a mistouch. In addition, the noise degradation is reduced by the structure of the resistor with very little error.

A large screw-type terminal is used for the speaker terminal in consideration of contact resistance and aging, and 4 mm thick cable can be used for this terminal.
The input pin jack uses a gold-plated terminal with low contact resistance and little change over time.

Since the TA-N9 is a complete DC amplifier configuration, if the preamp connected to the TA-N9 has a DC leak, the DC detection of the power amplifier will move or the vibration system of the speakers will change. To cope with this problem, the TA-N9 has a C-Coupled terminal, which cuts frequencies below 1.5 Hz at -6dB/oct. with a capacitor that has been carefully examined in terms of phase characteristics and sound quality.

A glass-epoxy substrate with excellent electrical and mechanical properties is used.
In addition, the copper foil of the pattern is also 175 μ thick to emphasize the sound quality.

Model Rating
Type Monaural power amplifier
Circuit system Amplifier : Pure complimentary service SEPPPDC Amplifier
Power supply part : pulse lock power supply
Effective output (20 Hz to 20 kHz) Class A Operation : 80W (8 Ω, 0.005% distortion factor)
Class B Operation : 450W (8 Ω, 0.007% distortion factor)
Maximum effective power
(20 Hz to 20 kHz, Distortion Factor 0.03%)		 Class A operation : 100W (8 Ω)
Class B operation : 500W
Harmonic distortion factor 0.007% or Less (Effective Output)
Intermodulation distortion factor (60 hz : 7 khz = 4 : 1) 0.007% or Less (Effective Output)
Damping factor 300 (1 kHz, 8 Ω)
Residual noise 22 μ V or Less (8 Ω, A Network)
Signal-to-noise ratio (closed circuit
A network, 8 ohm)		 Class A operation : 120 dB or more
Class B operation : 128 dB or more
Frequency characteristic DC ~ 300 khz + 0 -1dB (for Direct)
Input Sensitivity / Impedance Class A operation : 1.1V/50k Ω
Class B operation : 2.5V/50k Ω
Speaker impedance Class A operation : 8 Ω ~ 16 Ω
Class B operation : 4 Ω ~ 16 Ω
Semiconductor used Transistor : 72
MOS FET : 10
FET : 1
IC : 7
Diode : 55 Pieces
Power supply voltage 100 VAC, 50Hz/60Hz
Power consumption 450W
External dimensions Width 480x Height 185x Depth 500 mm
Weight 18kg
Attachment Power cord