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Witness the DDS revolution -“ Advanced RF technology and latest digital know-
how join forces in this ultimate FM stereo tuner. The front end easily handles even
very high signal levels. An Advanced DGL Detector delivers high performance
and is fully adjustment-free. DS-DC based on digital signal processing assures ideal
stereo demodulation performance. Choose between manually operated pulse tuning
and 32-station memory. Explore the many other impressive features.
The range of available program sources is getting
ever more varied: SA-CD, CD, DVD, net-based
music distribution, to name but a few. But FM
broadcasts still have a special role to play, since
they cover the entire spectrum from live
performances of time-honored classical works to
the latest hits. The FM band provides a rich choice
of music all day long. In recent years, many local
stations have come onto the scene, covering
community events and using the live broadcast
medium to its best advantage.
Many audiophiles and music lovers were wishing
for the re-appearance of a truly high-class tuner
to complement a modern-day audio system and
provide the means to enjoy FM broadcasts with
optimum sound quality. By developing new circuit
components and applying its innovative thinking
to circuit topology, Accuphase has created a
product that meets and exceeds these
expectations. The T-1000 is an FM stereo tuner
of the highest order. It represents a bold fusion
of advanced RF technology with latest digital
finesse.
The newly developed front end employs the
revolutionary DDS (Direct Digital Synthesis)
principle in the local oscillator. In addition, the
DS-DC type stereo demodulator performs all
necessary operations through software-based
arithmetic processing in a DSP microprocessor.
This radically new approach to circuit design
results in amazing S/N ratio and channel
separation, elevating FM tuner performance to a
new level. Convenient features such as a 32-
station memory, digital output, and balanced
output circuitry are further advantages that ensure
pure signal transmission without any sound
DDS
Local
Oscillator
Attenuator
From
MicroprocessorDouble
Balanced
MixerIF Amplifier
INPUT
Comparator EX-OR OUTPUT LPF
RF removal
Delay circuit with 24 high-speed C-MOS
ICs features wide linearity range High-
speed High-speed "Exclusive OR"
C-MOS IC
Point a in
Fig. 2
Point b in
Fig. 2
Point c in
Fig. 2(Input signal)
(Delay signal)
(EX-OR output)
When input signal a is non-modulated, the
EX-OR output c is at parity and the
averaged output of the low-pass filter is 0
(zero).EX-OR output is
open if 10 or 01,
closed if 00 or 11When input signal a is modulated, the EX-OR output
c is at non-parity. The integral value after the low-
pass filter represents the potential change indicated
by the slanted line (audio signal).
Sine wave
dataD/A
converter
Quartz
oscillatorFrequency
divider Output
Fig. 1 Front end circuit diagram
quality degradation. The T-1000 is the ultimate
luxury-class FM tuner representing a successful
blend of sound quality, performance, and
ergonomics.
Dual-stage tuning front end easily deals with
very high signal levels
nDouble-tuned antenna circuit prevents cross
modulation interference at high input levels.
nFET-based RF amplifier is configured as a
cascode circuit with low feedback.
nInput gate features an attenuator that prevents
overload even in close proximity of strong
transmitters.
Revolutionary DDS principle in local oscillator
achieves exceptional S/N ratio
An FM tuner amplifies the signal from the antenna
input in an RF amplifier and then mixes it with the signal from a local oscillator for conversion
into the intermediate frequency (IF). In the T-1000,
the local oscillator is a highly advanced DDS
(Direct Digital Synthesis) circuit. Unlike
conventional PLL circuits, DDS does not use
feedback, allowing it to produce an output signal
whose frequency accuracy is exactly the same
as that of the quartz oscillator itself. Because no
unwanted frequency modulation components are
present in the IF stage, the Super Heterodyne
front end achieves drastically improved S/N ratio.
The output of the quartz oscillator is supplied
to the frequency divider to create the timing (in
other words the sampling frequency) with which
the sine wave data are read out.
Using this sampling frequency, the sine wave
data are read in the D/A converter to create the
analog waveform output.
Because there is no feedback loop, the
frequency purity of the D/A converter output can
be kept identical to that of the quartz oscillator.
The FM (frequency modulation)
detector is a so-called Advanced
DGL (Differential Gain Linear)
detector developed by Accuphase.
This circuit delivers superb
performance (minimal distortion,
high S/N ratio) while requiring
absolutely no adjustment, assuring
optimum reliability.
As shown in the diagram at right,
the input stage employs a high-
speed comparator in the 2.5 MHz
wide-band amplifier, to eliminate
beat interference. The delay circuit
achieves outstanding stability
through the use of 24 high-speed
C-MOS ICs.
High-performance Advanced DGL Detector
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Channel
Separator
Crosstalk
Double Cancellation
Crosstalk
Cancellation
(1st stage)
L
R
Pilot Tone
Direct
Synthesis
Crosstalk
Cancellation
(2nd stage) Stereo modulated signal
Pilot tone
DS-DC (Direct Synthesis - Double Cancellation)
DS-DC principle with DSP ensures ideal stereo
demodulation for amazing channel separation
The stereo demodulator in the T-1000 features
another Accuphase innovation called DS-DC (Direct
Synthesis - Double Cancellation). The demodulator
comprises the two technologies described at right.
Since all operations are carried out through software-
based arithmetic in a DSP (Digital Signal Processor),
ideal demodulation performance can be achieved,
resulting in previously unheard-of channel
separation. A AA A
APilot Tone Direct Synthesis
Commonly, an FM tuner employs a PLL circuit to extract the pilot tone and obtain the
frequency and phase components from the input signal (stereo-modulated signal). If the
level of the pilot tone decreases, noise will be heard and stereo separation becomes
extremely poor.
With DS-DC, the waveform of the pilot tone in the input signal is identified as is (-œ½) and
generated directly by the DSP arithmetic. Consequently, the pilot tone can be extracted
reliably even when a high level of noise is present. Good stereo separation can be achieved
even when the pilot tone level is low.
-œ½ Identification here means to analyze the signal and determine similarities.
B BB B
BCrosstalk Double Cancellation
After the input signal has been separated into the left and right components, the circuit
eliminates crosstalk using a dual approach that also takes phase components into
consideration. The result is extremely thorough left/right separation.
n nn n
n DS-DC type stereo demodulator
n nn n
nSupplied Remote Commander RC-33
Stereo separation characteristics
Allows tuning, storing and recalling
stations, and controlling all other functions
of the tuner.
