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 speakersare 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 661 Receiver

 Sansui 661 FM/AM Stereo Receiver
When Sansui announced the price of this revolutionary new FM/AM stereo receiver, many high-fidelity experts were greatly surprised, just as you were. The name Sansui has long meant innovation and excellence in sophisticated audio electronics. But it has also meant, usally, that any high-fidelity equipment bearing the Sansui name also carried an expensive price tag.   But now, thanks to a startling innovation called CBM (Circuit Board Module) developed specifically by Sansui for finest professional studio equipment, you can forget price and concentrate on the outstanding Sansui quality and performance of the all-new 661.
This is a budget-prieced stereo receiver that delivers "expensive" tonal quality and performance. Its power amplifier is of a very advanced all-stage direct-coupled OCL design providing RMS continuous power of 27 fully useable watts per channel (total music power 110 watts) with a surprisingly wide power bandwidth of 15 to 40,000Hz with very low overall distortion. Its MOS FET equipped tuner and highly versatile preamplifier and control sections with two stereo tape record/monitor circuits stereo AUX inputs and much more would normally mean a far higher price tag. Check out the details of these and other features of the Sansui 661 - your best bargain in Sansui stereo excellence.

 Improved performance and Reduced Costs with Sansui's CBM
Sansui's CBM (Circuit Board Module) technique greatly increases electronic capability and dependability, reduces wiring and size and significantly lowers the expense of quality-controlled mass-production of highly sophisticated electronic circuits. In tur, this means that the construction and chassis assembly of the 661 can be performed in less time and at greater savings to you. The 661 incorporates four CBM units, one each for its tuner, preamplifier, power amplifier and power supply sections. Many ordinary receivers with considerably higher prices require up to a dozen complicated and potentially troublesome circuit boards to achieve the same results.

FM Fronted with FET and Linear Variable Capacitor
A dual-gate low-noise MOS FET (metal oxide semiconductor FET) and a frequency-linear variable capacitor are used in the RF amplifier stage of the FM tuner in the 661. These combined with its 3-transistor converter stage composed of a local oscillator and buffer circuit, each regulated by a separate constant-voltage power supply provide excellent distortion characteristics, superior signsl-to-noise ratio and very high FM sensitivity.

FM IF Amplifier with Two Bi-resonator Ceramic Filters
The 661's IC-equipped FM IF amplifier provides high station selectivity and reception of both local and distant FM signals with exceptional clarity. The super-wide selectivity bandwidth (1,1MHz peak to peak) and the sharp cut-off ceramic filters in its circuits have vastly improved the dynamic range of the FM section.

 Newly Developed IC Equipped FM Multiplex Demodulator
The 661's new FM multiplex demodulator features a high-density IC for improved stability. Stereo separation is better than 35dB and THD in stereo FM reception is less than 0,7%. An FM de-emphasis switch inside the chassis allows the 661 to be easily converted for ideal reception of FM signals anywhere in the world.

AM Tuner Section
The enhanced selectivity and sensitivity of the AM tuner in the 661 results from the use of newly-developed, highly selective coils and a bi-resonator ceramic filter in its IF amplifier stage. The tuner's design also eliminates the annoying whine and boom of AM reception.

Stabilized FM/AM Tuner Power Supply with Ripple Filters
Both the FM and the AM sections of the 661 benefit from the elimination of ripples and fluctuations in power supply thanks to a new stabilized supply technique. This results in a greatly improved signal-to-noise ratio, as well.

Smooth-Tune Mechanism and Linear Tuning Scale.
An attractive easy-to-raed black-out dial panel of glare-free smoked glass is provided on the 661. Its tuning scale is FM linear, calibrated in equal sections of 250kHz each for easy and fast reading. An oversized, brightly-lighted signal-strength meter facilitates both AM and FM tuning. The smooth tune dial mechanism in the661 has been engineered to incorporate an extra-large flywheel, special tension mechanism and dial string of no-stretch/no-shrink polyester for stability under all temperature and humidity conditions.

 Direct Coupled Low-Noise Phono Equalizer
Carefully-selected low-noise silicon transistors are used in the phono equalizer amplifier of the 661 to provide excellent signal-to-noise ratio, minimum distortion and wide dynamic range. Its phono overload capacity an important factor in any phono equalizer for it determiners the ability of the unit to respond properly to all signals no metter how strong or weak, is as high as 150mV RMS (420mV p-p), allowing a wide dynamic range and reducing THD to less than 0,5%

More Precise Control of Tone
The bass and treble tone controls in the 661 are of the CR type in a carefully-engineered design to minimize distortion and provide more precise control of tone coloration.

Two Tape Record/Monitor Circuits with Reprinting and Stereo AUX
The 661 feature two separate tape recording and monitor circuits. Thes are capable of handling two stereo tape decks at the same time and permit tape-to-tape reprinting from Tape-1 to tape-2 at the touch of a switch. Tape-1 can be connected either through the pin-type jacks provided or through the DIN socket while Tape-2 can be connected directly or coupled with  a 4-channel adaptor (decoder). Separate tape monitor controls are provided  on the front panel. The 661's stereo AUX circuit also can come in handly for connecting an extra tape deck, cartridge tape player, additional tuner or a number  of other units.

 Independent Power Amplification
The all-stage direct-coupled OCL semi-complementary power amplifier provided in the 661 affords dependable and extremely clean stereo power to drive even the largest of stereo speaker systems. The differential amplifier in the largest of stereo speaker systems. The differential amplifier in the initial stage and the dual plus/minus power supply system greatly improves the performance of this advanced system. You have at your command a full 27 watts of continuous RMS power per channel (into 8 ohms at 1kHz, both channel driven). Its power bandwidth is surprisingly wide -from 15 to 40,000Hz- while its THD and Intermodulation figures are both held to a low, low 0,5% or less.

Superior Power Supply and Power Protection Circuits
Since the power supply for the 661's power amplifier is entirely independent from those which feed its preamplifier and tuner sections, two oversized capacitors of 4700µF each and an extra large, closely-regulated power supply transformer see that this supply remains stable and always available. The vital power transistors in the all-stage direct-coupled OCL power amplifier are protected from damaging power surges with several elaborate power protection devices. These include four quick-acting fuses and a positive action relay circuit. The latter also acts to protect your valuable speakers from damage or from the annoying "popping" noise by providing a momentary delay between the time the 661 is switched on and the release of any signal to those speakers.

Other SpecialFeatures of the 661 Receiver
Stereo/Mono Mode Switch - which also by-passed FM multiplex demodulator when it is turned to Mono position.
Balance Control - to provide continuous balance of left and right channels.
Loudness Switch - adjusts for low-volume listening
High Filter - to eliminate tape hiss and record surface noise.
Stereo Headphone jack - for private listening
FM Muting Switch - to eliminate inter-station noise during FM tuning.
Terminals for Two Pairs of Stereo Speakers - A and B with position for A,B or A + B
Two AC Outlets (one switched)
Attractive Champaigne-Gold Front Panel - with user-oriented control display
All-Wood cabinet- -with cushioned no-mar feet.

Audio Section
Power Output (at rated distortion)
Music Power (IHF) : 110 W (4Ω, 1kHz);  75 W (8Ω, 1kHz)
Continuous Power
Each Channel Driven : 40/40 W (4Ω, 1kHz);  32/32 W (8Ω, 1kHz)
Both Channels Driven : 27 +27 W (8Ω, 1kHz);  20 +20 W (8Ω, 20-20,000Hz)
Total Harmonic Distortion (at rated power output):
Overall (fromAUX) : less than 0,5%
Intermodulation Distortion (at rated power output, 70Hz : 7,000Hz = 4 : 1 SMPTE method)
Overall (from AUX) : less than 0,5%
Power Bandwidth (IHF):  15 to 40,000 Hz
Frequency Response (at 1 Watt power output)
Overall (from AUX) : 15 to 30,000 Hz,  +1  -2 dB
Equalization (at tape rec output):  RIAA Curve (30 to 15,000 Hz ±1 dB)
Load Impedance:  4 to 16 Ω
Damping Factor:  60 (8Ω)
Channel Separation (1kHz at rated power output)
Phono : better than 45 dB
Aux : better than 45 dB
Hum and Noise (IHF)
Phono : better than 70 dB
Aux : better than 80 dB
Input Sensitivity and Impedance (1kHz for rated poer output)
Phono : 2,5 mV/ 50 kΩ (Max. Input capability 150 mV at rated distortion)
Aux : 100mV/50 kΩ
Play Pin Jacks : 100 mV/50 kΩ
Rec/Play DIN Socket : 100 mV/50 kΩ
Tape-2 (4-ch adaptor)
Play Pin jacks : 100 mV/50 kΩ
Recording Output
Rec Pin Jacks : 100 mV
Rec/Play DIN Socket : 30 mV
Tape-2 (4-ch adaptor)
Rec Pin Jacks : 100 mV
Switches and Controls
Bass : +10 dB, -10 dB at 50 Hz
Treble : +10 dB, -10 dB at 10,000 Hz
Loudness : +10 dB at 50 Hz;  +8 dB at 10,000 Hz
High Filter : -10 dB at 10,000 Hz (6 dB/oct)

Tuner Section
FM Mode
Tuning Range:  88 to 108 MHz
Sensitivity (IHF):  2,2µV
Total Harmonic Distortion
Mono : 0,5%
Stereo : 0,7%
Signal-to-Noise Ratio:  better than 60 dB
Selectivity:  better than 50 dB
Capture Ratio:  2,5 dB
Image Rejection:  better than 55 dB at 98 MHz
IF Rejection:  better than 60 dB at 98 MHz
Supurous Response Rejection:  better than 60 dB at 98 MHz
Spurious Radiation:  les than 34 dB
Stereo Separation:  better than 35 dB at 400 Hz
Frequency Response:  30 to 12,000 Hz;  +1 -3 dN
Antenna Input Impedance:  300Ω balanced (75Ω unbalanced)
AM Mode
Tuning Range:  535 to 1,605 kHz
Sensitivity (Bar Antenna):  50 dB/m at 1kHz
Selectivity:  better than 28 dB at 1MHz
Image Frequency Rejection:  better than 80 dB/m at 1Mhz
IF rejection:  better than 80 dB/m at 1MHz

Power Requirements
Voltage : 100,117, 220, 240 V  50/60 Hz
Consumption : 70 W (rated), 210 VA (max.)
Dimensions (W x H x D):  444 x 135 x 300 mm (17-1/2" x 5-3/8" x 11-13/16")
Weight:  10 kg (22,0 lbs ) Net;  12,4 kg (27,3 lbs) Packed

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