What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Sansui SF-1

Omni-Radial Sound Field Speaker System

The sound-in-theround speaker system. For the person who wishes his 4-channel sound system to truly be be sound-in-the-round, Sansui is pround to introduce a system that takes this new music form to its thrilling sound pinnacle. The SF-1 Omni-Radial Sound Field Speaker System is not just another omnidirectional speaker, but a completely new concept in 360 degree sound, for it employs speakers facing both upwards and downwards and makes use of specially-designed reflectors to diffuse the reproduced sound in complete horizontal and broad vertical directions. 

This 2-way 3-speaker system produces a vibrant and reverberant 4-channel system. Among its virtues, it has been designed to accurately reflect the very important, but often overlooked "indirect" sound waves of music reproduction. And these indirect waves are the vital element of the live concert hall sound field. The authentic "live" sound effect that so many speaker systems promise but so few deliver. In addition, sound diffusion is extended in the SF-1 by the use of a new porous foam acoustic diffuser placed behind the Kumiko fretwork grille, a device which also helps to attain ideal dispersion of sound in the very high frequency range. Beautifully designed and finished (like its larger twin speaker system,the SF-2), the SF-1 cabinet is made of solid natural wood and hard chipboard, specially treated to resist heat or stains. The system is actually an expensive piece of fine furniture - and looks it. From the most respected name is stereo, Sansui.

Sansui's Sf-1 system is designed to achieve rich ambience by radiating sound in a full 360 degrees so that it will be reflected off of more surfaces, and so that the distinctively directional signals in the sound will intermingle with the reflected sounds with fine time or phase lags.
How does it achieve this sound radiation?

The SF-1 features a unique tetrahedron construction. Its two woofers and single tweeter are on the same vertical axis.
Sounds emanating by them are dispersed in complete 360-degree horizontal directions - and in broad vertical directions as well - by a top and bottom reflector. When the sounds reach the grilles located on the four sides of the system's enclosure, their vertical distribution is broadend even more by a newly developed porous foam acoustic diffuser.
The result of this new technology is something totally unique in sound. No matter where you place the SF-1, sound literally envelops you from all directions, in a sense, you swim in sound, and it's an experience that does indeed make you wonder why someone hasn't thought of this speaker idea before. Another advantage of the SF-1: you may place it anywhere. No longer are you confined to the corners of your room as you decide where to place your speakers. Freedom, unlimited, for one thing. Sound unlimited, for another. And wouldn't you know that Sansui discovered it.

Two Woofers:  There is one 165 mm (6-1/2") woofer that faces upwards and another that faces downwards. Sound from them is dispersed by top and bottom reflectors in all directions, the better to reflect off of more surfaces (walls, ceiling, floor) and the better to enhance the great sense of ambience and naturalness which the SF-1 provides.
Sealed Tweeter:  This is a 58 mm (2-1/4") diameter unit completely sealed in the back by an over-sized cover to prevent it from interfering with the woofer located directly beneath it. The usually narrow dispersion of the tweeter sound is dispersed in a full 360 degrees by the top reflector above it. Overall, the speaker boasts excellent transient response and sound transparency.
Crossover Network:  The SF-1, despite its compact size, is truly an advanced system, far more versatile than any other omnidirectional speaker in its class or price range. Its crossover network possesses a 6 dB/oct. cut-off characterictic that enables the speaker system to prevent phase deviations between the woofers and tweeter and to provide a very smooth transition between these two different types of speakers. This network is equipped with a volume-type attenuator for the tweeter so that you may adjust that speaker's output level to suit room acoustics and your own listening taste.
Porous Foam Acoustic Diffuser:  This new type of material replaces the usual speaker system cloth cover. It is advantageous for any number of reasons, but especially because it enhances the sounds taht are vertically dispersed by the top and bottom reflectors and helps to diminish their harshness and bite. The end result is a mellow, natural, evenly distributed sound field that you would usually experience only during a live musical performance. 

Heat and Stain Resistant Cabinet:  The SF-1 is a beautiful piece of furniture as well as a beautiful sound experience. Built of solid natural wood and hard chipboard, its cabinet is specially finished on the surface to resist heat and stains. It will not discolor or fade if you accidentally place a coffee cup on it. In form and function, it is very near the peak of omnidirctional speaker systems, and is only exceeded in quality by Sansui's large system , the SF-2.
8-Meter (26-Foot) Long Connection Cable:  To allow you to position the speaker system anywhere in your room, the SF-1 comes with an 8-meter long connection cable. This is the expensive soild cabtyre type cable that gives added strength and effectively shields out noise.

Woofer :  2 x 165 mm (6-1/2") cone type
Tweeter :  1 x 58 mm (2-1/4") cone type
Power Rating:  45 W (Peak)
Impedance:  8 Ω
Sensitivity:  90 dB/W at 1 m
Frequency Range:  55 - 20,000 Hz ( in anechoic chamber)
Crossover Frequency:  2,000 Hz
Crossover Network:  2-way 6 dB/oct.
Dimensions (W x H x D):  370 x 563 x 370 mm (14-9/16" x 22-3/16" x 14-9/16")
Weight:  12,0 kg (26,5 lbs) net; 14,3 kg (31,5 lbs) packed
Finish:  Solid natural wood open pore.

Sansui AU-9900

The AU-9900 is one of the largest and most advanced of any integrated stereo pre/power amplifiers yet introduced in the popular Sansui AU Series, instruments created to deliver the famed Sansui tonal quality al. The high power output levels demanded by today's true audiophiles.

Parallel Push-Pull Power Output Section.
The power amplifier section of this robust stereo component features a diferential amplifier and a 3-stage Darlington system designed in the parallel push-pull format. The results include a continuous power output of 80 watts, min. RMS, per channel, both channels driven into 8 ohms, over a 20 Hz to 20 kHz bandwidth with no more than 0,08% total harmonic distortion.

Stablized, Well-Regulated Power Source
The power supply section is one of the most stable and dependable ever developed, providing plus-minus symmetrical voltages to all circuits as needed. Oversized power capacitors help provide extra stability, while the use of an advanced toroidal transformer further assures better power regulation and exceptionally low induced hum.

Excellent R.I.A.A. Equalization
The phono equalizer consists of two amplifying sections each with a differential amplifier. High frequency roll-off  is made by the CR type circuit and low frequency turn-over is made by the NF type circuit, most accurately and with very low distortion.

Effective Triple Tone Control
Sansui's popular Triple Tone Control circuit is featured in the AU-9900 to provide the best, most flexible tonal adjustment control yet developed. Twelve  trans istors are used in the circuit, itself built around an initial stage using, a differential amplifier. The individual controls for Bass, Midrange and Treble are made still more convenient by the selectable turnover switches for Bass (600 Hz, 300 Hz or 150 Hz) and Treble (8 kHz, 4 kHz or 2 kHz).

Quadruple Protection Circuits
Changes in temperature, line voltage supply or shorts in speaker leads or terminals are instantly detected and can cause no damage to the power transistors or connected speakers thanks to the use of four separate protection circuits. These are: [1] a temperature sensing circuit, [2] a DC voltege detection circuit, [3] an ASO (Area of Safety Operation) circuit, and [4] an overload detection circuit.

Tone Defeat Switch
Like the AU-20000 and AU-11000, this integrated amplifier provides the convenience of being able to cancel all tone control adjustments instantly with a Tone Defeat Switch
Two-Stepped Low/High Filters
The low Filter has positions for 12 dB/oct. attenuation at 20 Hz or 60 Hz;  the high Filter is selectable for 6 dB/oct. cut-off at 7 kHz or 12 dB/oct. cut-off at 12 kHz

Other Valuable Features
Teh AU-9900 provides every convenience needed for professional and semi-professional use, included are a hand-trimmed precision volume comtrol, input/output terminals for up to two stereo decks, with full monitoring and deck-to-deckdubbing, a quick-access Tuner Switch, Mode Switch, Level Selector (0 dB/ -10 dB/ -20 dB) and an Audio Muting Switch.

Power Output (min. RMS, both ch. driven, 20-20,000 Hz, no more than 0,05% T.H.D.):
80 watts per channel into 4 and 8 ohms
Load Impedance: 4 and 8 ohms
Power Bandwidth:  20 - 20,000 Hz (at or below rated min. RMS power output and T.H.D.)
Total Harmonic Distortion (overall from AUX): less than 0,05% (at or below rated min. RMS power output and T.H.D.)
Intermodulation Distortion (70 Hz : 7 kHz = 4:1 SMPTE method):
Overall (from AUX) less than 0,05%
Frequency Response (at 1 watt):
Overall (AUX to power output) 10 to 50,000 Hz +0 dB, -1 dB
RIAA Curve Deviation (Phono):  +0,3 dB, -0,3 dB (30 to 15,000 Hz)
Channel Separation (at rated output 1,000 Hz):
Phono 1 and 2 :  better than 55 dB
Tuner :  better than 60 dB
Aux 1 and 2 :  better than 60 dB
Power Amplifier:  better than 70 dB
Tape Monitor :  better than 60 dB
Hum and Noise (IHF):
Phono 1 and 2 :  better than 65 dB
Tuner :  better than 80 dB
Aux 1 and 2 :  better than 80 dB
Power Amplifier:  better than 100 dB
Tape Monitor :  better than 80 dB
Input Sensitivity/Impedance:
Phono 1 :  2 mV, 4 mV, 8 mV / 30 k, 50 k, 100 k Ω
Phono 2 :  2 mV/ 50 k Ω
Max.input Capability:  more than 300 mV rms 0,1% distortion
Tuner :  130 mV /50 k Ω
Aux 1 and 2 :  130 mV / 50 k Ω
Tape Pb  1 and 2 :  130 mV (PIN)
Tape Pb 2 :  130 mV (DIN)
Recording Output:
Tape 1 :  130 mV (PIN)
Tape 2 :  130 mV (PIN); 30 mV (DIN)
Bass :  +10 dB; -10 dB at 30 Hz
Midrange :  +5 dB, -5 dB at 1,500 Hz
Treble:  +10 dB, -10 dB at 20 kHz
Tone Selectors:
Bass :  150 Hz, 300 Hz, 600 Hz
Treble:  2 kHz, 4 kHz, 8 kHz
Low :  -3 dB at 20 Hz (12 dB/oct); -3 dB at 60 Hz (12 dB/oct)
High :  -3 dB at 7 kHz (6 dB/oct); -3 dB at 12 kHz (12 dB/oct)
Muting:  0 dB; -20 dB
Level Set: 0 dB; -10 dB; -20 dB
Power Requirements
Voltage :  100; 120; 220; 240 V , 50/60 Hz
Consumption:  180 watts Rated
Dimensions ((W x H x D):  460 x 160 x 375 mm (18-1/8" x 6-5/16" x 14-49/64")
Weight [net/packed]:  18 kg (39,7 lbs)/ 20,3 kg (44,8 lbs)

Sansui TU-9900

Professional class tuner for superior stereo receeption under any kind of broadcast conditions.
The   elegance of these tuners speaks for itself because they are deigned to complement the amplifiers you choose. Sansui's indepth research contributes a lot and has helped keep phase distortion down and FM selectivity high, for all of the tuners in the range. The control this tuner gives over an incoming signal puts it into a class way above that of an ordinary FM stereo receiver. With the TU-9900it's very much like having a private line between the tuner and the FM stereo broadcasting studio. The TU-9900 is the ultimate in tuner sophistication. But the same Sansui thought goes into all of the Tuners. This tuner not only look good. Slanted tuning dials, separate signal/tune meters, smooth dial mechanisms and many other convenince features make them a pleasure to use.

Dependable Plus-Minus Power Supply
Musical reproduction from broadcast sources depends heavily on correct and accurate power supply circuitry. The TU-9900 'finst of the Sansui TU Series' incorporates an elaborate feedback type stabilized power supply section for this very reason. It is of the plus-minus dual supply type to guarantee ideal circuit performance at all times.
Superlow Distortion, 0,06%
A wide-band ratio detector and a PLL circuit in the FM multiplex demodulator are employed for lower phase deviation. The TU-9900thus boasts aa very low distortion figure of 0,06% (mono) and 0,08% (stereo) in FM operation to bring its performance up to the quality required by the very best amplifier components.
Selectable FM IF Bandwidth
To enhance both the tonal quality and the reception ability of the TU-9900, Sansui has provided a switch to select either a Wide or Narrow FM IF bandwidth. In the former, two 6-pole LC block filters are put on line to improve the sound quality; in the latter, a narrow-band ceramic filter is added for more effective rejection of adjacent signals.
Automatic Noise Canceller
When receiving weak (or remote) stations, this circuit automatically blends the left and right signals in optimum proportion to the strength of an incoming broadcast to deliver the same noise-free reception of any station regardless of its strength.

High-Performance FM Front-End
The TU-9900 features a sensitivity of 1,5 µV (IHF) thanks to its linear-frequency 5-gang variable capacitor and the three dual-gated MOS FETs and a transitor employed in the high-performance FM front-end.
Quality AM Reception
AM broadcast are received cleanly and quietly with the lowest noise or interference possible thanks to the use of a double-tuned circuit and a dual-element, dual-coil ceramic filter in the AM section.
Positive Action Tuning
The feel and accuracy of the special tuning mechanism in the TU-9900 will be appreciated for years of hard and frequent use. It features an oversized tuning knob a special tension mechanism, and a heavyweight, high-inertia sintered iron flywheel.
Special Features for Tape Recording
Tape buffs will appreciate these three special features:
1.A built-in recording test signal generator is provided to facilitate pre-recording calibration of optimum recording levels.
2.A low-pass filter is included to prevent the carrier frequencies of FM broadcasts from interacting with the bias frequencies of decks in use, thus avoiding the annoying "beat" noise otherwise heard. The filter can be defeated by a front panel switch when not recording.

Other Important Features:
The TU-9900 has an FM Antenna Attenuator Switch to cut down the strength of excessive incoming signals; a Multi-Path Detection circuit to help align antennas, highly accurate Twin Tuning Meters, FM Muting Switch, Dolby FM output terminals, and an Output Level Control.

FM Section
Tuning Range:  88 - 108 MHz
Sensitivity:  1,5 µV (IHF); 0,9 µV (DIN)[1 kHz, mod.30%,S/N26 dB]
Max. Input Capability:  more than 130 dB
Quieting Slope:
Mono Wide :  37 dB 1,5 µV, 51 dB 3 µV
Narrow :  37 dB 1,5 µV, 51 dB 3 µV
Stereo Wide :  39 dB 10 µV, 53 dB 50 µV
Narrow :  40 dB 10 µV, 54 dB 50 µV
Total Harmonic Distortion
Mono Wide :  less than 0,06% (at 1 kHz); less than 0,06% (at 50 Hz); less than 0,08% (at 10 kHz)
Narrow :  less than 0,05% (at 1 kHz); less than 0,05% (at 50 Hz); less than 0,08% (at 10 kHz)
Stereo Wide :  less than 0,08% (at 1 kHz); less than 0,1% (at 50 Hz); less than 0,15% (at 10 kHz)
Narrow :  less than 0,8% (at 1 kHz); less tha 0,8% (at 50 Hz); less than 1,2% (at 10 kHz)
Signal-to-Noise Ratio
Mono :  better than 80 dB
Stereo :  better than 76 dB
Wide :  better than 55 dB (at 400 kHz); better than 22 dB (at 300 kHz); better than 5 dB (at 200 kHz)
Narrow :  better than 90 dB (at 400 kHz); better than 60 dB (at 300 kHz); better than 20 dB (at 200 kHz)
Capture Ratio:
Wide :  less than 1,0 dB
Narrow :  less than 3,0 dB
AM Suppression:  better than 58 dB
Image Frequency Rejection:  better than 100 dB at 98 MHz
IF Rejection:  better than 110 dB at 98 MHz
Spurious Response Rejection:  better than 110 dB at 98 MHz
Spurious Radiation:  less than 34 dB
Stereo Separation: 
Better than 50 dB at 1 kHz (30 dB at narrow)
Better than 40 dB at 50 Hz (30 dB at narrow)
Better than 40 dB at 10 kHz (30 dB at narrow)
Frequency Response:  30 to 15,000 Hz, +0,5 -0,8 dB
Antenna Impedance; 
Balanced :  300 Ω
Unbalanced : 75 Ω
FM Antenna Attenuator:  -30 dB
AM Section
Tuning Range:  535 - 1605 kHz
Sensitivity (Bar Antenna):  45 dB/m at 1,000 kHz
Selectivity:  better than 70 dB at 1,000 kHz (±10 dB)
Image Rejection:  better than 100 dB/m at 1,000 kHz
IF Rejection:  better than 100 dB/m at 1,000 kHz
Total Harmonic Distortion:  less than 1% at 80% Modulation 100 dB/m
Semiconductors:  39 Transistors; 3 FETs, 7 Ics, 39 Diodes, 1 Zener Dioda; 5 LEDs
Power Requirements:  100,120, 220, 240 V, 50/60 Hz
Power Consumption:  20 watts rated
Dimensions (W x H x D):  460 x 160 x 310 mm (18-1/8" x 6-5/16" x 12-1/4")
Net :  9,6kg (21,2 lbs)
Packed :  11,3 kg (24,9 lbs)

Sharp Optonica ST-3636

Optonica ST-3636 features:
FM IF AMP. Section
FM Front-End Circuit
FM IF  Band with Selector Circuit
FM Tuning Auto-Lock Circuit
FM Detection Sections (Quadrature Detector Circuit)
Hi-Blend Circuit
Low-Frequency Amplifier Circuit
Power Supply Circuit
Audio Muting Circuit

FM Detector Circuit. This unit employs "Quadrature Detector" based on newly developed IC, which is substituted for ratio detector and Foster-Seeley's detector that have been sp far used. The basic structure of quadrature detector circuit is as shon.

Multipath Detection Circuit
Multipath Distortion. In any of electric-wave signals broadcasting including FM waves, it would be ideal if the signals emitted by abroadcasting station were caught by a receiver's antenne as they midway. Actually saying, however, there are practically some obtacles (like mountains and  skyscrapers, etc.) between the transniter side and the receiver side, which have the emitted signals undergo a phenomenon of waves reflection, leading to that the signals become distored variously when caughtby the receiver's antenna
A simple exampleconcering this distortion is that in the mountainous area or large cities full of higher buildings, the TV stes get produced images be doubled (this called a ghost). This phenomenon is a sort of multipath distortion and it is caused by the there is a time delay betweenthe direct waves and reflected waves. In the case of radio sets, this is reffed to as that the reproduced sounds contain distortions; particularlyas for stereo broadcasting signals, since their band width is rather wider and so they are apt to be interferred by various objects, not only the distorted sounds are produced but also the stereo separation characteristics will suffer. These phenomena are named a multipath distortion.

Multipath Distortion Detection. Multipath distortion are classified into the two, that is, phase distortion which is found out by the frequency discriminator and AM distortion which is removed by the limiter circuit; the latter AM distortion is actually subject to detection by the multipath detector circuit.

FM Stereo Demodulator Section
Features of PLL Stereo demodulator Circuit.
This set incorporates a stereo demodulator circuit that comprises ICs with the PLL (Phase Locked Loop) system applied. The PLL FM demodulator circuit is provided with such characteristics as mentioned  below.
In order to demodulate stereo composite signals, it is necessary to take a 19 kHz pilot signal out of the stereo composite signals and to make it a 38 kHz signal.  Most of the conventional methods to obtain such a 38 kHz signal are frequency doubling ones which utilize a nonlinearity of the elements. Compared with the conventional type, the recently developed IC-ed demodulator provides more sufficient separation effects.  However, since it also requires 2 or 3 coils like the conventional one, if even one of them is dislocated from the initially adjusted point due to a secular change the separation effects will be deteriorated. Moreover there is such a contradiction that the more the efficiencies of the coils are increased enough to withstand the outer pulse signals like automobil ignition noises, the more the coils suffer secular changes.
To eliminate such disadvantages as above, PLL system is employed in the method to make a 38 kHz signal using a 19 kHz pilot signal.

Variable Air Check Calibrator Circuit
Theis circuit is to make appropriate the recording level in advance when recording FM broadcast into the tape deck or equivalent.
The circuit  is reffered to as this variable air check calibratoe circuit and it is composed of an air check oscillator circuit, air check meter indication circuit and further a circuit by which, when the air check/muting switch is set to 'air check on' position during FM reception, the indication mode of the signal/air check meter will be changed from 'signal level' to 'air check level' indication.

FM Section
Tuning Range:  87,6 -108 MHz
IF:  10,7 MHz
Sensitivity (at SN 26 dB, 40 kHz deviation):  1,4 µV
Frequency Response:  30 - 15,000 Hz +1,5 -3 dB
Image Rejection:  110 dB (at 98 MHz)
IF rejection:  100 dB (at 98 MHz)
Selectivity [normal/wide]:  72 dB / 30 dB
Capture Ratio [normal/wide]:  2,5 dB / 1,5 dB
AM Suppression:  45 dB
Signal-to-Noise Ratio:  65 dB (40 Hz deviation)
Distortion [normal/wide]
Mono :  0,6% / 0,25%
Stereo:  0,8% / 0,4%
Stereo Separation:  42 dB (1 kHz)
AM Section
Tuning Range:  520 - 1620 kHz
IF:  455 kHz
Quieting Sensitivity:  400 µV/m
Image Rejection:  55 dB (at 1400 kHz)
IF Rejection:  50 dB (at 600 kHz)
Distortion:  1,5%
Audio Section
FM Output Voltage
Variable : 0 - 0,55 V
Fixed :  0,35V
AM Output Voltage:
Variable :  0 - 0,35 V
Fixeed :  0,2 V
Circuit:  Superheterodyne system, 2-band with PLL stereo demodulator
Featured:  FM muting, FM multipath detection, variable air check calibrator, FM auto lock, FM IF band selector circuit
Semiconductors:  28 Transistor, 36 Diode (1-zener diode); 4 ICs, 3 FET (dual gate, MOS type); 3 LED
Power Source:  AC 110/220/240V, 50/60 Hz
Power Consumption:  24 W
Dimensions (W x H x D):  442 x 144 x 373 mm
Weight:  7,5 kg