Accuphase T 109 Brochure

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MECUPLOSC

FM STEREO TUNER

T-109

.Uluamrecise electronic tuninQOFronl and with double-
tuned antenna circuit easily handles high signal levels.
Newly developed Advanced DGL DelectaIOExlvemely sta-
ble high-parlormance stereo decodLeIOSQ-stafion memory
also stores [sception seninQSOPulse tuning system

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Among the great variety of program sources
available today, such as CDs and LPs,
digital satellite broadcasts, or prerecorded
music tapes, FM broadcasts play a special
role, 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, and when received with state-of-the-
art equipment can rival the CD in sound
quality. The FM tuner therefore is an impor-
tant component in a stereo system
designed to enlighten and entertain.

The FM Stereo Tuner T-109 from Accu-
phase was conceived for the music lover
who accepts no compromises when it
comes to sound quality. It represents the
ultimate in FM reception technology. The
PLL electronic tuning system pulls in any
desired station with pin-point precision and
total reliability. A convenient memory func-
tion lets you store as many as 32 stations
including sensitivity and filter on/off set-
tings, and the pulse tuning principle devel-
oped by Accuphase blends digital accuracy
with the familiar feeling of operating an
analog tuning knob, The front end employs
a dual-stage design that can handle even
extremely high input signals without cross
modulation interference problems, and the
newly developed Advanced DGL Detector
assures high performance and rock-stable
reception. The stereo decoder takes
sophisticated circuit topology to new
heights, with its reference frequency pro-
vided by a ceramic resonator for utmost
stability. Since it would not do to dilute the
outstanding sonic virtues of this tuner fur-
ther down the signal path, a balanced
output stage sends the audio signal to the
next component without any sound quality
deterioration. And to top it off, the supplied
remote commander provides the come
nience of operating this top-notch tuner
from the comfort of your easy chair.

Ultra-precise electronic tuning

The T-109 tunes to the station frequency by
means of a quartz crystal oscillator that
operates with extreme precision and is
virtually free of time or temperature induced
drift. It precisely locks the tuner to the

tion and maximum sensitivity, Electronic
tuning also means that the T-109 is not
susceptible to modulation and other noise
caused by external vibrations.

Front end with double-tuned antenna cir-
cuit prevents cross modulation interfer-
ence

Each FM tuner has a front end that serves
to pick just the desired station out of the
crowded FM band and convert the radio
frequency into an intermediate frequency.
The design of this stage is highly crucial,
since it must discern and select minute
signals, while at the same time being able
to withstand the very high levels that can
occur when a strong station is broadcasting
nearby. Freedom from interference and

distortion is what makes the difference
between a run-of-the-mill product and a
sophisticated high-class FM tuner,

Figure 1 shows the circuit diagram of the
front end employed in the T-109, Accu-
phase has long been advocating the
double-tuned antenna circuit principle",
whereby a high selectivity circuit precedes
the antenna signal amplifier stage. This
prevents intermodulation distortion and
other undesirable
side effects which
can occur if a strong
signal were am-
plified directly. The
RF amplifier stage
uses FET devices
configured as a low-feedback cascode
amplifier. This means that two amplifying
elements are connected in a cascaded
arrangement with drastically improved fre-
quency response.

The input stage gate features

a PIN-diode attenuator that is
switched on or off by a micro-
processor, depending on the
level. This

to

w men antenna input
assures high-quality recep-
tion, free from interference

and distortion, even in areas
which are close to strong
mum broadcast stations that could

reception point that yields minimum distor-
m m

o.
mun
E i E % rams )-
_ a:
L Ammo

m
?osc
n

Fig.1 Circuit Diagram of Front-End

3,-4.1

otherwise overload the front
end. The balanced mixer
stage uses a push-pull FET
arrangement to minimize har~
monic distortion and reliably
reject interference signals.

Ultimate FM tuner offers numerous technology highlights: Front end
with double-tuned antenna circuit easily copes with high signal
levels. Newly developed adjustment-free Advanced DGL Detector.
Stereo decoder with ceramic resonator provides ultra high-
performance. 32-station memory also stores reception settings.

Newly developed Advanced DGL Detector
Ever since the invention of the frequency-
modulation principle, the most commonly
used detector types were Foster-Seeley or
ratio detectors. However, the evolution of
system quality and performance called for
other, more sophisticated detector tech-
niques. Accuphase answered this need
with the DGL (Differential Gain Linear)
detector adopted since the model T-106,
featuring low distortion, high S/N ratio, low
capture ratio, and reliable, adjustment-free
performance, For the T-109, Accuphase has
now further developed and refined the DGL
principle, resulting in the Advanced DGL
Detector.

Figure 2 (A) shows the circuit principle of
the Advanced DGL Detector. The input
stage uses a high-speed comparator as a
broadband 2.4 MHz amplifier to prevent
beat interference. The delay circuit con-
sists of 24 high-speed C-MOS ICs.

Figure 2 (B) illustrates the DGL operation
principle. The delay circuit takes the slight
output delay of high-speed logic ICs into
consideration. An arrangement of 24 ICs
delays the phase angle by 114 degrees to
assure minimum distortion and maximum
S/N ratio. The delayed signal ® is then
compared to the input signal @ by an
EXCLUSIVE OFl circuit which switches the
circuit on and off according to the electric
potential between the two signals. As a
result, the degree of condensation and
rarefaction of frequency» modulated signal
is detected digitally © and extracted as the
audio signal. Thanks to this approach,
linearity of the delay circuit is maintained
over a very wide range (:24 MHz), and
adjustment is not requiredI assuring excel-
lent long-term reliability. Another advantage
is outstanding differential gain linearity,

Switchable IF bandwidth (NORMAL, NAR-
ROW)

FM broadcasts have an audio frequency
range up to 15 kHz and S/N ratio of about
80 dB. To make the most of this impressive
quality potential, the T-109 normally uses
an IF stage with wide bandwidth (NORMAL)
to receive broadcasts. However, if there are
strong neighboring stations which might
impair reception, the IF bandwidth can be
switched to NARROW. In this position,
distortion and stereo separation are slightly
worse, but selectivity is maximized to
ensure sharp reception.