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





Optonica ST-4405 tuner

Optonica ST-4405 in an AM/FM stereo tuner ; featuring a stereo beacon, LED FM center channel tuning indicator, 5-step LED signal strength indicator, and an FM Air Check 400 Hz output tone for presetting of a recorder's level controls. One set of variable line level outputs is provided.
The front panell hasonly one control: for tuning. The output level control is lockated on the rear apron. Front panel switches are provided for power, AM, FM mono, FM Auto (mono/stereo), FM muting, hi-blend (MPX noise filter), and Air Check.
The FM antenna input is 75/300 ohms. A rod antenna and external connection are provided for Am. One unswitched AC outlet is provided.

Performance
Full limiting was attained with 4,8 µV. For 300 Ω and "Tee" antennas the monophonic high fidelity sensitivity (60 dB quieting) measured 10 µV. The stereo high fidelity sensitivity 955 dB quieting) was 70 µV.
At standard test level the stereo frequency response measured +1/-1,8 dB from 20 to 15,000 Hz. Distortion depended on the tuning adjustment beacause the "center channel indicator" illuminates over a relatively large tuning range. Monophonic distrtion ranged from 0,15%  to 0,25%  T.H.D. stereo distortion ranged from 0,15% to 0,3% T.H.D. the Signal-to-Noise ratio measured 71 dB. Stereo separation was +40 dB . Selectivity was good.
The maximum output level corresponding to 100% modulation of the transmiter was 0,8 volts.
The Air Check output level was 0,55 volts; 3,5 dB below the stereo and mono output level corresponding to 100% modulation of the transmitter. For particularly clean recordings we suggest the recorder be adjusted to indicate no higher than -4 dB (below 0-VU/0-dB) when feeding the Air Check signal
Though stations can be received 9with considerable noise) below 3,4 µV input, the LED FM center channel indicator requires at least 3,4 µV before it turns on. The 5-step signal strength indicator requires at least 5,5 µV before the first (lowest value) step illuminates.
AM tuner performance is generally average, with higher than average sensitivity to signals on the high end of the dial.

Overall dimensions measured:  16-15/16" (wide), 2-21/32" (high); 15-1/2" (deep). 
Weight is 11 lbs.

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