Stereo
Reciver with SQL Quartz-Locked Tuning and High Speed DC amplifier
The Sanyo
Plus 55 is elegant proof that moderate power and reasonable price in a stereo
receiver do not inevitably mean compromise in
performance or features. Every aspect of its design, both internal and
external, has been painstakingly worked and reworked to achieve a harmony
seldom found even in far more to operate without being oversimplified. The
controls are logical and responsive. The front panel gives visual display of a
wealth of important information. And the internal circuits are the best that
today's technology has to offer. The Sanyo Plus 55 is truly the perfect rceiver
for the audio connoisseur with power requirements in the 50-60 watt per channel
range.
Tuner
Section
Digital Plus
Tuning
Unquestionably,
the most striking feature on the Plus 55's handsome front panel is its unique
dual-mode frequency display. Sanyo engineers knew that digital frequency
readout was a necessity for completely accurate, unambiguous tuning. At the
same time, they realized that many people do not know the exact frequencies of
their favorite stations, and find it easier to remember the approximate dial
pointer location for each station. So sanyo Digital Plus tuning includes both a
conventional dial scale and a bright fluorscent digital frequency display,
which travels with the illuminated pointer along the dial scale as the receiver
is tuned. Digital Plus thus combines the convenience of analog tuning with the
precision of digital, and is a Sanyo Plus series exclusive.
SQL
Quartz-Locked Tuner Circuitry
The Plus 55
incorporates Sanyo's unique Sampling Quartz-Locked tuning system, which
provides accuracy impossible to achieve with conventional tuner designs. The
special AT-cut quartz crystal locks in stations, with no significant drift due
to time or temperature changes.
LED Signal
Indicators
Conventional
tuning meters are replaced in the Plus 55 by an array of light emiting diodes.
Signal strength is indicated by a 5 LED 'bar graph' display, while a separate
LED indicates when the SQL system has achieved 'lock' on a given FM frequency
(equivalent to a center-channel indicator). Both displays use high gain,
DC-coupled voltage comparators for precise indications.
Dual-gate
MOSFET RF amplifier
Sanyo solves
the problem of FM front-end overload by using a dual-gate MOSFET
(metal-oxide-silicon field effect transistor) in the front end circuitry. One
of the device's gates recelves the antenna signal, while the second is driven
by a DC voltage from the tuner's Automatic Gain Control circuit. Thus the RF
gain is automatically reduced in the presence of strong signals, avoiding
overload and cross-modulation distortion and keeping other stations from
interfering with the one you want.
Advanced IF
design
Outstanding
performance in the Plus 55 's IF section is achieved by a combination of Sanyo
IC's and 3 sophisticated ceramic filters. These solid state resonators provide
extremely good rejection of unwanted signals, plus 'linear phase'
characteristics in the passband (essential for low distortion in the audio
program). A quadrature FM detector and Phase Locked Loop multiplex decoder
assure outstanding stereo separation without the need for periodic realignment.
The result is clean, clear listening and years of trouble-free reception.
Combined
muting/mode switch
When stereo
mode is selected, FM muting is automatically engaged to screen out stations
which are too weak for enjoyable stereo listening. Muting is defeated in mono
mode.
Dolby FM
demphasis switch
A rear panel
switch changes the tuner's FM deemphasis characteristic from the standard 75 µs
to 25 µs for proper decoding of Dolbylized broadcasts with an external Dolby
adaptor.
Preamplifier
Section
High
performance phono preamp
After years
of intensive development Sabnyo has perfected an integrated circuit with ideal
characteristics for handling low level phono cartridge signals. The Plus 55
phono circuit easily achieves an astonishing 87 dB Signal-to-Noise ratio
(re10mV input), frequency response to 150 kHz , and distortion below 0,01%
under most conditions. The differential first stage has anexceptionally wide
overload margin (150 mV at 1 kHz) to easily handle high output cartridges and
the extremely demanding transient peaks found on direct-to-disc and digitally
mastered recordings. The differential configuration also isolates the RIAA
equalization network from the phono input, to avoid frequency response errors
caused by interaction of cartridge impedance with the network. Precision
resistors and capacitors are used to hold RIAA equalization eror to a maximum
of ±0,2 dB. Records sound the way they should, no matter which cartridge you
prefer to use.
Versatile
tone controls and filters
Bass and
treble controls on the Plus 55 are of the Baxandall feedback type, and combine
wide adjustment range with an almost total absence of interaction; even at
maximum cut or boost, their effect on th emiddle of the spectrum is less
than1/2 dB. You can adjust bass and treble without upsetting the tonal balance
of the rest of the music.
The Plus 55
is provided with an 8 kHz high filter useful for removing hiss and scratches
from noisy programs, and a 12 dB/octave subsonic filter to remove record warp
and arm resonance signals.
These
inaudible signals can consume large amounts of amplifier power, creating
distortion of audible bass and putting a severe load on woofers. The loudness
control provides moderate bass and treble boost at low volume settings to
compensate for the ear's reduced sensitivity to these frequencies.
Two tape
deck inputs with dubbing
The Plus 55
allows recording and monitoring with two tape decks, as well as dubbing from
one to the other at the push of a button.
Power Apm
Section
High Speed
DC amplifier
Except for
the DC blocking input capacitor, the Plus 55 power amplifier is totally direct
coupled from first stage to speaker terminals. Frequencies from 5 to 150,000 Hz
are reproduced with virtually no phase distortion. Musical signals are
reproduced exactlly as recorded, for the ultimate in realism.
Exclusive
Sanyo Hybrid IC power stage
Sanyo's
pioneering work in high power integrated circuit design now makes it possible to put the entire power output stage
of one channel of the Plus 55 in a single compact hybrid IC. Using a fully
complementary, Darlingto-connected circuit configuration, the power stage
achieves ultra-low distortion, outstanding waveform symmetry, plus a fast 60
V/µs slew rate to prevent transient distortion. Close mounting of the hybrid
components on a copper plated aluminum substarate assures ideal thermal
tracking of all components, for better bias stability and greater
reliability than an equivalent discrete
circuit.
LED power
indicators
These
attractive 5-LED 'bar graph' displays give instantaneous indication of right
and left channel output level. The LED's response time is far faster than any
mechanical meter, and special 'peak-stretching' circuits make sure that even
extremely short transisnts are visible to the eye. Amplifier output and
possible overload canbe monitored precisely and easily. A range switch
increases the sensitivity of the indicators by 10 times, for useful readings at
low listening levels.
Speaker A/B
switching
Allows
connection and operating two pairs of speakers separately or simultaneously.
Ecxcellent performance with 4 Ω loads permits running most popular speakers in
parallel without loss of power or sound quality.
4-way output
protection
A protective
relay locked between teh amplifier output and the speaker terminals operates to
disconnect the load under any of the following conditions.
When the
unit is first turned on ( after a 5 second delay for the circuits to stabilize
the speakers are reconnected)
When the
heat sink temperature becomes too high for safe operation ( due to inadequate
ventilation or sustained overload)
When special
protection circuits sense the presence of a DC voltage at the outputs (which
can quickly damage speakers)
In addition,
current monitoring circuits operate to instantly shut down th epower stage if,
for any reason, the output current should reach an unsafe level.
Specifications:
Amplifier
Section
Continuous
Power Output (minimum sine wave RMS per channel at 8 Ω, 20 - 20,000 Hz no more
than 0,04% T.H.D.): 55 watts into 8 Ω;
60 watts into 4 Ω
Maximum
Total Harmonic Distortion (from 250 mW to rated power into 8 Ω, 20 - 20,000 Hz,
Aux input): 0,04%
Intermodulation
Distortion (rated power, Aux input, 60 Hz : 7 kHz= 4 : 1): 0,04%
Input
Sensitivity/Impedance:
Phono : 2,5 mv/47 k Ω
Aux, Tape 1
and 2 : 150 mV/47 k phm
Frequency
response:
Phono (RIAA
standard curve): ±0,2 dB
Aux, Tape
: ±0,5 dB (20 - 20,000 Hz); ±1 dB (10 - 40,000 Hz)
Signal-to-Noise
Ratio (IHF-A weighted)
Phono (at 10
mv): 87 dB
Phono (at
2m5 mV) : 75 dB
Aux, Tape :
95 dB
Damping
factor: 40 (1 kHz, 8 Ω)
Residual Hum
and Noise at Speaker Outputs: 0,6 mV
Transient
Response (Slew Rate): 60 volts per microsecond
Phono
Maximum Input Capacity (1 kHz): 150 mv
RMS
Tone
Controls
Bass : ±10 dB at 100 Hz
Treble
: ±10 dB at 10 kHz
Loudness
Control (Vol. -30 dB)
100 Hz / 10 kHz :
+8 dB /+3 dB
Filters
Subsonic (30
Hz) : -12 dB/oct
High (8 kHz)
: -6 dB/oct
Output
Voltage
Tape Rec 1
and 2 : 150 mV
FM Tuner
Section
Frequency
Range: 88- 108 MHz
Usable
Sensitivity [mono]: 10,8 dBf (1,9 µV)
50 dB
Quieting Sensitivity
Mono : 13,7 dBf (2,7 µV)
Stereo
: 37 dBf (39 µV)
Maximum
Signal-to-Noise ratio
Mono : 75 dB
Stereo
: 70 dB
Total
Harmonic Distortion [Mono]:
At 100 Hz
: 0,2%
At 1 kHz
: 0,2%
At 6 kHz
: 0,35%
Total
Harmonic Distortion [Stereo]:
At 100 Hz
: 0,35%
At 1 kHz
: 0,3%
At 6 kHz
: 0,4%
Frequency
Response: 20 Hz - 15,000 Hz, +1 -2 dB
Alternate
Channel Selectivity (at ±400 kHz): 75 dB
Capture
Ratio: 1,2 dB
AM
Suppression Ratio: 55 dB
Stereo
Separation [1 kHz / 10 kHz] : 45 dB / 35
dB
Spurious
Response Rejection (98 MHz): 80 dB
Image
Rejection ratio: 70 dB
IF Rejection
Ratio (98 MHz): 90 dB
Muting
Threshold: 5 µV
AM Tuner
Section
Frequency
Range: 525 - 1620 kHz
Usable
Sensitivity (Ferrite External Antenna):
300 µV/m - 30 µV
Signal-to-Noise
Ratio (at 5 mV/m): 45 dB
Selectivity: 35 dB
Image
Rejection ratio (1000 kHz): 50 dB
IF Rejection
Ratio (1000 kHz): 45 dB
General
Section
Power
requirements: AC 120V, 60 Hz / Ac 220 -
240 V 50/60 Hz
Power
Consumption: 200 W
AC Outlets
[switched/unswitched]: 1 x 100 W max./ 1
x 100 W max.
Dimensions
(W x H x D): 18-7/8" x 5-1/4"
x 11-1/2"