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

Sony TC-K61

The Sony TC-K61 is an outstanding expression of Sony’s ability to deliver the latest and best in tape. The K61 provides the superlative speed constancy of Sony’s two-motor drive system, controlled by a logic microprocessor IC. The microprocessor, which receivers commands via feather-touch pushbuttons, executes them via transport solenoids. The result is smoother operation, gresater flexibility, and the capabilities for timer operation and remote control. Moreover, the K61 incorporates Sony’s exceptional Sendust and Ferrite record/play head, four-gap erase head, LED Peak Program Meters, and a host of electronic refinements. Yet for all its sophistication, the TC-K61 remains easy to operate - and reasonable in price.

Low-Distortion Electronics
Sony’s attention to detail is evident in the electronic design of the TC-K61. For example, the critical playback head amplifier uses a unique, patented, direct-coupled design, which improves phases linearity and lowers distortion. The power supply employs an FET-buffer circuit for constant-current drive, even when the household voltage itself varies. And the K61 provides a switch for low and normal Type Ibias, in addition to a four-position tape selector switch. Even the selection of electronic parts reflects Sony’s commitment to the best possible sound. The power supply incorporates fast-recovery diodes that minimize noise. The equalization amplifier uses expensive metal film resistors and polypropylene capacitors. Finally, the headphone/line output control uses a stepped attenuator, with discrete, potted resistors for the lowest noise possible.

 Sony Dolby IC
A high-quality Dolby noise reduction circuit typically requires about 100 separate parts, including transistors, resistors, and capacitors. Sony has replaced all of these parts with the newly developed Sony Dolby IC, the CX-174. Made with Sony’s unique “Process V” wafering technique, the Dolby IC exhibits exceptionally pure chemical composition. This helps the CX-174 realize lower distortion, wider dynamic range, and better tracking linearity.
In addition, conventional Dolby Circuits use a record/playback slide switch, which can introduce noise. In contrast, the CX-174 works in conjunction with a relay switch that is quieter and more reliable than the conventional slide switch. To further maintain this recording accuracy, the TC-K61 incorporates a switchable multiplex filter. When you record FM stereo broadcasts, the filter can be switched on to prevent the standard 19 kHz FM pilot signal from interfering with the Dolby system. At all other times, the filter can be defeated for optimum high-frequency response

Microprocessor-Controlled Transport
The sophisticated two-motor transport is, in turn, controlled by a microprocessor IC logic system. Feather touch pushbuttons provide convenient, foolproof mode selection. You can go quiclky from one mode to another, without going through Stop. The logic circuit checks each command for proper sequencing, and protects the tape and mechanism from undue stress. The logic circuit also facilitates ‘Punch-in” recording of new material onto a previously recorded track. End-of-side sensing for All-mode Auto-Stop can be accomplished with Sony’s non contact Luminous Sensor.

Two-Motor System
Because tape speed irregularity can be heard as wavering sound, unvarying tape drive is essential to high-fidelity cassette recording. For this reason, the Sony TC-K61 uses two discrete DC motors to move the tape across the heads. This division of labor eliminates any irregularities caused by variations in tape supply tension, and reduces the number of mechanical linkages needed in the transport mechanism. The spooling motor drives the reel hubs and provides fast winding. This high-torque motor works in conjunction with the magnetic clutch assembly to provide not only quick fast-forward and rewind, but also extremely gentle tape handling.
The second motor, which drives the capstan, incorporates Sony’s famous brushless and slotless (BSL) design for uncommonly even delivery of torque increases and decreases as a result of spaces - “slot” - between the electromagnets. This wavering-force effect is called “cogging”. Sony has eliminated cogging with the remarkable BSL motor. There are no brushes, no slots, and the magnetic force is smooth and constant. As an additional benefit, the absence of motor brushes makes the BSL motor unusually quiet and trouble-free.
As with the TC-K44, the K61 uses a frequency-generator (FG)servo system. In the K61, a tiny FG has been incorporated into the BSL motor. As the motor turns, the generator produces an AC signal whose frequency is proportional to the motor’s speed. In this way, the FG reports any speed irregularities to the servo control electronics, which in turn, governs the motor speed. Thus, even slight speed variations are corrected - before they can affect the sound.
This advanced drive system is completed by an oversize dynamically-balanced, anti-resonant flyhweel. The die-cast, zinc flywheel incorporates a nonmetallic compound to dampen resonance, and thus helps to minimize modulation noise caused by the transport mechanism. As a result of these precautions, the K61 can maintain smooth tape travel under a wide variety of temperature and mechanical load conditions. The audible pfoof of the system’s excellence is clear, unwavering sound, and a measured wow and flutter of only 0,04% (WRMS)

Auto-Space/Record Mute
To provide absolute silence between recorded selections, teh TC-K61 incorporates a unique Auto- Space/Record Mute control. The control can be used to automatically attain a timed, four-second space unwanted program material, such as FM commercials, with four seconds of silence, or insert longer or shorter gaps, as desired.

Auto Play and Memory Cue
Another convenience of the K61’s transport is Auto Play. Auto Play allows you to preset teh deck to transfer from rewind into play at the beginning of the tape, by simply touching the rewind and play buttons simultaneously. With the memory feature selected, the K61 can be put into rewind and it will stop automatically when the tape counter reads ‘999’. Or with Memory Cue, you can touch the rewind and play buttons simultaneously to have the deck rewind to ‘999’ and transfer into the play mode automatically.

Timer Operation
With an external timer, the K61 can be set to record or play back automatically, at a predeterminated time. You can have the K61 record FM broadcasts in your absence, or even wake to music from your high fidelity system. Unlike other timer provisions, the number of recording or playback operations in the unattended period is limited only by the capacity of the timer.

LED Meters with Two Types of Peak Hold
Like the TC-K44, the K61 incorporates Sony’s sixteen-segment LED Peak Program Meters, whose parallel-bar arrangement shows channel balance at a glance. In the K61 however, the meters’ range is calibrated from -40 dB to +8 dB, and there are two methods of holding the highest-peak indication. In the automatic mode, the peak-hold re-sets after 2,5 seconds, or when a higher peak is established. Or, if you wish, you can set the meters for manual hold, at the touch of a button.

Specifications TC-K61
Number of Heads: Two
Head Type (Rec/Play): S&F
Erase Head Type: 4-Gap Ferrite
Bias Adjustment: 2-Position Switch for Type I
Drive Type: Belt
Motor Type: Capstan - BSL; Spooling - High-Torque
Meter Type: Peak LEDs 16 x 2 parallel
Fast-Forward/Rewind Time (C-60): 80 sec.
Wow and Flutter: 0,04% (WRMS); 0,12% (DIN 45507)
Frequency Response (-3 to +3 dB, Re: -20 dB):
Metallic Tape : 30 - 17,000 Hz
FeCr Tape : 30 - 17,000 Hz
EHF Tape : 30 - 16,000 Hz
SHF Tape : 30 - 14,000 Hz
Frequency Response at Re 0 dB:
Metallic Tape : 30 - 13,000 Hz
Signal-to-Noise Ratio (Dolby NR Off, Re: 3% THD, Peak, IHF-A weighted):
Metallic Tape : 59 dB
FeCr Tape : 59 dB
EHF Tape : 57 dB
SHF Tape : 52 dB
Improvement with Dolby NR On : Up to 5 dB at 1 kHz, 10 dB at 5 kHz or Above
Total Harmonic Distortion (1 kHz, Re: 0 dB Record Level):
Metallic Tape : 1,0%
FeCr Tape : 1,0%
Crosstalk (1 kHz, tracks): 60 dB
Separation (1 kHz, channels): 35 dB
Erasure (400 Hz, incl. Mettallic Tape): 60 dB
Bias Frequency: 105 kHz
Meter Range: -40 , +8 dB
Line Input Sensitivity/Impedance: 77,5 mV/50 k Ohms
Mic Input Sensitivity/Impedance: 0,25 mV/Low
Line Output:
Level ‘Fixed’: 435 mV
Level ‘Variable’: 27,5 - 435 mV
Line Output: Load Impedance, Nominal: 50 k Ohms
Load Impedance, Minimum: 10 k Ohms
Headphone Output Level: 4,9 - 77,5 mV
Nominal Headphone Impedance : 8 Ohms
Power Requirements: AC 120 V, 60 Hz
Power Consumption: 26 W max
Dimensions (W x H x D): 430 x 130 x 290 mm (17" x 5-1/8" x 11-3/8")
Weight: 5,6 kg (12 lbs 5 oz)
Full-Function Remote Control: RM-50 (optional

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