Accuphase E-460 Handmatig - Pagina 3
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AAVA (Accuphase Analog Vari-gain Amplifier) Volume Control
AAVA is a radically different volume control principle that eliminates all variable resistors from the signal path and provides top-notch performance and sound quality.
Because the music signal is not affected by changes in impedance, high signal-to-noise ratio and low distortion are maintained at any volume control setting.
Volume control resolution
■
AAVA adjusts the listening volume by means of 16 weighted V-I converter amplifiers which are
controlled by current switches. The number of possible volume steps set by the combination of these
converter amplifiers is 2 to the power of 16 = 65,536.
■
Input buffer amps use 5-MCS topology
One of the factors that have a bearing on possible noise in an AAVA arrangement is the input buffer
design. By connecting five high-performance amps in parallel, excellent S/N ratio is assured.
AAVA maintains high S/N ratio and uniform frequency response
■
Unlike with conventional volume controls, AAVA does not introduce a change in impedance at any
volume setting. Consequently, there is no deterioration of S/N ratio, and frequency response remains
totally uniform. The benefits are especially apparent at settings that correspond to normal listening
levels, because the tonal quality is not altered in any way.
■
No more left/right tracking differences or crosstalk
Because AAVA is an electronic circuit employing fixed-value resistors, there is virtually no left/right
tracking error also at low volume levels. Since channels can be kept separate, crosstalk also does not
present a problem.
AAVA operation principle
The music signal is converted into 16 types of weighted current by
V-I (voltage - current) converting amplifiers [1/2, 1/2
The 16 currents are turned on or off by 16 current switches, and the
combination of switch settings determines the overall volume. The
switching operation is controlled by a CPU according to the position
of the volume control knob. The combined signal current forms a
variable gain circuit that adjusts the volume. Finally, the combined
current is converted back into a voltage by an I-V (current - voltage)
converter.
■ CPU assembly which controls AAVA and various other functions
■ AAVA volume control assembly
with higher integration density
of components and circuitry
■
■
■
■
2
15
16
, ... 1/2
, 1/2
].
BUFFER
INPUT
5-MCS
Input music signal
AAVA means analog processing
The AAVA circuit converts the music signal from a voltage into a current, switches gain by means of
current switches, and then reconverts the current into a voltage. The entire process is carried out in the
analog domain.
Same operation feel as a conventional high-quality volume control
The volume control knob position is detected by a dedicated CPU which in turn selects the current
switches for AAVA operation. Operating the knob therefore feels exactly the same as with a
conventional control, and as before, operation via the remote commander is also possible.
Attenuator and balance control also implemented by AAVA
The functions of the attenuator and the left/right balance control are covered by the AAVA circuit as
well, eliminating the need for additional circuit stages. Keeping the configuration simple helps to
maintain high performance and sonic purity.
Display shows volume level as numeric value
The volume level (degree of attenuation) as set with AAVA is shown as a numeric indication in the
center of the front panel. The indication ranges from MAX (0 dB) to MIN (lowest setting).
16 current switches
(65,536 possible combinations)
1
−
2
1
−
2
2
1
−
2
3
1
−
2
15
1
−
2
16
V- I Converter
CPU detects position of volume
Conversion into current with 16
knob and operates current on/off
16
weighting stages (1/2 - 1/2
)
switches according to knob position
■ Supplied remote commander RC-200
AAVA configuration in E-460
I-V Converter
Reconversion of
current into voltage
＋
OUTPUT
Current values
are added
Volume knob is turned
and position is detected
Allows volume adjustment and
input source switching.