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

A&R Cambridge T21

The T21 Stereo FM Tuner
The qualities of the A60 amplifier series demand a tuner that is a complete partner. The T21 is that partner, an ideal match in looks, performance and price.

Great care has been taken in the design of the sound circuitry of the T21 to produce an unusually flat frequency response over the critical listening bandwidth. A "birdie" filter, fitted before the stereo decoder, considerably reduces the unpleasant whistles ("birdies") caused by closely positioned stereo broadcasts it also compensates for phase errors in previous stages which would otherwise add to distortion and crosstalk. A highly efficient ,ultiplex filter removes the 19 and 38 kHz high frequency tones produced by the stereo decoder circuitry, preventing damage to loudspeakers and interference with the bias oscillator in a tape recorder.

Overall, our design and production standards have been carefully maintained with the T21 tuner. We beliwve it is the perfect complement to our range of high performance, value-for-money sound equipment.
T21 also included in the tuning window is a single red LED as a stereo beacon. Tuning can be carried out by either the manuall tuning control or one of the five preset push buttons. Full station search with continuously variable tuning is provided by the rotary knob which has a pleasant and useful flywheel action. For the more frequently used stations each of the five buttons can be individually preset with the controls at the rear of the tuner. A mute facility is provided to remove background noise between the stations. To ensure that a station, once selected, remains accuraattely tuned in, an AFC (automatic frequency control) is fitted.

The  T21 can be used with any amplifier including of course, the A60 itself. A level controll knob on the rear of the tuner allows unwelcome variation in the output volume between the tuner and, say, a record deck to be equalised. Thus only minimal adjustment of the amplifier's volume control is ever needed. Both 75 Ω and 300 Ω balanced serial sockets are provided together with tuner matching plugs, allowing easy connection to all standard FM aerial systems.

Tuning Scale:  21 matched red LEDs in steps of 1 MHz, a gradual changeover in light intensity between adjacent LEDs allows frequency readings of typically 0,2 MHz to be achieved.
Tuning Range:  87,5 - 108,5 MHz
Signal Strength Meter:  bargraph scale using 5 LEDs, 2 red and 3 green
Tuning Meter:  3 LEDs, red-green-red
Stereo beacon:  single red LED
Aerial Inputs:
Socket for 75 Ω and 300 Ω antenna
Sensitivity (IHF):  1,3 µV
-3 dB Limiting Point :  10 µV
Capture Ratio:  1,5 dB
Alternate Channel Selectivity:  better than 60 dB
Repeat Spot Suppression:  better thann 80 dB
IF Rejection:  better than 80 dB
AM Suppression:  better than 50 dB 
(ref. 75 kHz deviation, 30% AM at 400 Hz, aerial signal  10 µV-10 mV)
Signal-to-Noise Ratio (CCIR/ARM weighted):
Mono :  better than 70 dB
Stereo :  better than 68 dB
Pilot Tone Suppression :  better than -50 dB
Subcarrier Suppression:  better than -40 dB
Total Harmonic Distortion (1 kHz):
Mono :  better than 0,15% (typically 0,08%)
Stereo :  better than 0,25% (typically 0,15%)
Channel Separation:  better than 40 dBf
Frequency Response:  20 Hz - 12 kHz  ±0,5 dB ( typically -3 dB at 15 kHz)
Channel balance:  within ±1 dB
Output Level:  continously variable 10 mV- 1 V at full deviation
Output Impedance:  less than 1 k Ω
Recommended Load:  better than 10 k Ω
Power Supply;  200 - 250 V  AC, 6 VA maximum; (or  100 - 120 V AC)
Deimensions (W x H x D):  450 x 60 x 240 mm (17-3/4" x 2-3/8" x 9-1/2")
Weight (net):  3,3 kg (7,3 lb)

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