FMbroadcasts which offer avariety of good music day inand day out are just as important asdisc records tomost audiophiles asahigh quality program source. To receiveandreproduce them tothe highest perfection that advanced engineering techniques permit, Kensonic Laboratory first introduced the Accuphase T·l 00 AM-FM Stereo Tuner which received
such highrecognition. Now we have alsodeveloped the Accuphase T·10l, and exclusive FM Stereo Tuner. for the many FM fans who appreciate
good music and better sound. Our basic policy indeveloping the T-l0' was the same as that for the
T-lOO - that is. to develop a tuner that "can bring the broadcasting studio right into the home." This, of course.meanta tuner that was
capable to separating allnoise and distortion that have mixed with the FM signal during itstransmission to the receiver. andreducing them to below audible level. while faithfully retaining the original broadcast quality. Italso meant'a tuner that would not be affected by external
factors such as temperature, humidity and varying input levels, nor a
lapse of time and one with aperfectly smooth tuning mechanism. In addition. extra special attention was paid to the following two points in designing theT-l01.
(,) Relation between selectivity and distortion. New IHF standards for tunerscall for measurement of selectivity. not only at 400 kHz, but also at 200 kHz, since many new stations are
increasing the problem of adjacent channel selectivity at 200 kHz. l-lowever, improvement of selectivity at the latter point adversely affects
: phase characteristics. andnecessitates acompromisewith distortion evel. Moreover, itisexpensive to make high sensitivity compatible with low distortion even for acompromise solution, due to the high cost of required elements.
Since adjacent channelinterference is not aproblem with every FM station, however,wedeveloped avariable selectivity tuner and con
centrated our design on sharp selectivity for reception that requires critical separation, andstressed lowest distortion for reception where
there is no noise elimination problem. I nshort, we came up with asingle
tuner that could be switched to give maximum performance priority to either selectivity or low distortion, depending on the nature of the incoming signal. Evenwhen concentrating on selectivity, however, we
never lostsight of the fact that "Hi-Fi" reception wasa primary aim.
(2) Checking the
quality of the incoming signal The quality of an incoming FM signal isvery important for high quality reception. Eventhebest tuners will not beable to correct adistorted FM input signal. For this reason an independent Multipath Meter was
provided on the front dial with which multipath effects on input signal quality canbechecked andcorrected.
1. High stability front end. The FM signal from theantenna entersthe RF amplifier where itis amplified after beingselected by the tuning circuit. Itisthen mixed with thelocal oscillator signal inthe mixer circuit and converted into a10.7 MHz IF signal. This circuitry isknown as the front end, and itfunctions ;the "brain" of the tuner. Weaksignals are amplified, strong signals are ssed through without adding distortion, and all types of noise
interference arereduced toinsignificant levels. The front end of the T-101 isequipped with afrequency linear 4·gang
variable capacitor. dual gate MOS FET transistor circuitry andlocal oscillator that is isolated by abuffer circuit. It guarantees high performance characteristics that include wide dynamic range input, spurioussignal rejection over 100 dB andimage rejection over 80 dB. Its 245 mm long dial scale ismarked off at 250 kHz intervals and permits smooth. easy tuning together with aprecision dial mechanism that is absolutely free ofbacklash.
2. Variable selectivity 1F circuit The 10.7 MHz signal from the front endenters the I Fcircuit where itis amplified, and the amplitude controlled signal isthen sent on to the detector circuit. In addition to its amplifying function. the IF circuit also blocks the passage of unwanted noise andinterference' such as the strong signals of anadjacent station. The T·101 hasavariable selectivity I Fcircuit which is comprised of anewly developed lQ·element linear phase lumped filter andasharp selectivity piezoelectric filter to carry out this function. Only the linear phase lumped filter is used under normal conditions. When adjacent station interference isencountered, the Selectivity Switch can beset to NARROW to add the piezoelectric filter. This effectively reduces this interference andproduces clearreception of the desired
when the SELECTIVITY switch is set to NARROW, distortion is still less than 0.5 %(monophonic reception at1 kHzl. and sound quality does not deteriorate. The NARROW position causes a slight deterioration in distortion ratio. which. for all practicable purposes, isnegligible. The Selectivity Switch should beset to NORMAL when there isno interference. It isthe position which provides highest quality, distortion·free reception.
3. Wideband detector circuit The amplified signal from thelinear phase lumped filter and the IFamplifier isthen demodulated into adistortion·free audio signal inthe detector stage. Itfeatures a discriminator circuit that has an extra wide bandwidth of1200 kHz. This isthree
times the normal range and isabig factor In greatly improving stereo
4. Phase locked loop stereo demodulator The demodulated audio signal is then separated into left and right channel stereosignals by anewly designed phaselocked loop stereo demodulator that has no coil-capacitor circuits. This stereo demodulator automatically synchronizes the phase of the broadcast pilot signal with that of thesubcarrier oscillator, and provides high stability, goodstereo
separation andbig improvement ofother stereo characteristics.
5. Independent Multipath Meter An independent Multipath Meter isprovided besides aSignal Strength Meter andaCenter Tuning Meter. This meter helps to check and correct multipath interference which can
cause stereo distortion and poor reception.
6. Other features.
This tuner has aStereo Only switch besides a Muting Switch andaStereo
Noise Filter. Itprovides both fixed level andvariable outputs so that a
Tape Deckcan be connected directly to the former andan amplifier to the latter. Detector output terminals arealso available wherea demodulator canbe
connected to enable reception with this tuner of FM 4-channel broadcasts when they arestarted inthe future.
.THE MOOELS ARE PHOTOGRAPHED IN WOODEN CABINET
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