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M-AX10
7.3 DESCRIPTIONS
7.3.1 Product Overview
Features of this product
Three-mode drive power amplifiers
This product is equipped with power amplifiers for two right and
two left channels (total of 4 channels).
Three types of speaker drive formats can be selected.
1. SEPARATE mode
The product functions as a 4-channel power amplifier (115 watts, 4
ohms for each of 4 channels). By connecting to a 2-way channel
divider, a high-grade multi-amplifier system can be established.
Using two units of this product provides a Hi-Fi surround system
for up to 8 channels. The product can also be used for DVD multi-
channel audio, DOLBY DIGITAL, and DTS applications.
2. DUAL mode
By connecting speakers that conform to tandem-wiring use, a Bi-
amplifier (tandem amplifier) system can be established. By driving
tweeters and woofers separately with different amplifiers,
interference between speaker units is virtually eliminated. Thus,
super hi-fi stereo playback with a high degree of purity is enabled.
3. BRIDGE mode
The product functions as bridge-output high-power amplifiers (230
watts, 6 ohms for each of 2 channels).
Symmetrical twin-stereo structure
High-performance stereo amplifiers are symmetrically mounted left
and right.
Of course in SEPARATE or DUAL mode, enlargement of a large
current loop can be eliminated even in BRIDGE mode, restraining
sound degradation due to magnetic coupling, which is a disadvantage
of bridge amplifiers. The important parts are isolated by shield plates
and shield cases to achieve excellent channel separation at high
frequencies (104 dB or more at 20 kHz between the left and right
channels). You can enjoy high-grade stereophonic playback in a
rich sound field.
Advanced direct-energy MOSFET power
amplifiers
This product employs MOSFETs of larger capacity than with
conventional models. For insulation between each large heat sink
and MOSFET, a quite small zero-resistance ceramic sheet is
employed to improve the radiation characteristics. Not only a rise
in temperature with continuous signal input, but also instantaneous
rises in temperature with pulse-type input can be minimized.
For higher sound quality, the response speed to an input of large
sound volume and the clarity are highly improved.
In addition, a newly developed Z (ZETT) BIAS circuit that precisely
reproduces the thermal factors of a MOSFET is mounted for
temperature compensation for the idle current. This drastically
improves the drift of the idle current which may greatly affect sound
quality, and enables playback at constantly stable sound quality
immediately after you turn on the power.
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Wide-range linear circuit
The wide range linear circuit has been enhanced to improve DC
stability by newly employing highly accurate parts of 0.5% error
and single-chip dual transistors for a completely discrete structure
that uses no DC servo or operational amplifier.
This enables natural and clear playback of low frequencies by
keeping NFB stable from very low frequencies.
DAC (Digital Accurate Control) attenuator
A high-precision 12-bit D/A converter of ladder resistance type is
used.
Advantages of the DAC attenuator (when compared with
conventional mechanical sliding-type controls)
1. Excellent S/N in practical usage
2. The frequency response is not affected by the attenuation volume
setting.
3. The attenuation volume can be programmed. This product
provides two curves, for high-frequency attenuation in a multi-
amplifier system and for normal volume control.
4. No tracking error (gain error between channels)
5. No signal irregularity from vibration, providing pure sound
6. The operation block and the circuit block can be separated. The
signal path length can be minimized by free layout.
Large-sized super ring toroidal transformer
A large-sized super ring toroidal transformer of 450 VA is employed
for the lowest possible loss and lowest impedance at the power block.
In addition, repression of power harmonics, which has been regarded
as impossible with large-capacity toroidal transformer, has been
achieved, enabling powerful and smooth playback at high speeds.
Silent control microcomputer
When the knobs and buttons are not operated, the control
microcomputer enters Low-Power-Consumption mode (system clock
oscillation stops). This decreases power consumption, and eliminates
high-frequency interference caused by clock oscillation to maintain
high sound quality. In addition, the microcomputer continuously
monitors the amplifier status and if it detects an abnormality, it
immediately activates the protection circuit. By using the
microcomputer in combination with the conventional hardware-
protection circuit, higher reliability and safety are ensured.
Ultra-Low-Impedance Power Circuit
Power de-coupling by an ultra-low-impedance condenser, ample
jumper lines and a No. 16 wire power cable are employed for very
low impedance in the power and ground lines.
In the low frequency range, channel separation is greatly improved
(achieving 115 dB at 20 Hz) by decreasing ground common
impedance.
In the high frequency range, the rise in impedance due to the
inductance component is suppressed, for higher frequency stability.
Thus a power amplifier that is virtually impervious to changes in
speaker impedance and connection cables has been created.
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