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





Dual C839 RC cassette deck

The Dual 839 is so different from all other cassette decks that, rather than list its many features, we'll guide you through them as if the 839 were in front of you.
First, the 839 is bi-directional in record and playback. This doubles the length of every cassette. You'll notice there's no door between you and the cassette compartment. Insert a cassette and it will lock in precise alignment.
That's Dual Direct Load and lock system. (a subtle but important touch; any slack in the tape is immediately taken up.)
Follow us carefully on his next one. Even when the tape is in motion, you can pull it out and replace it with another,  and the previous mode resumes automatically. Useful? When the tape nears the end at a crucial moment, you can have a new tape in place without missing beat.
The 839 is just as innovative in playback. If a tape made on another deck is too sharp or too flat, no problem. Playback pitch can be varied over an 8 percent range.  And previously recorded tapes with clicks, pops and disc jockey interruptions can be cleaned up electronically - smoothly and permanently. Dual's fade/edit control lets you do that with complete confidence, because it functions in playback.
Back to recording. He peak-level LED indicators react faster than any other metering system. And more accurately, because they're equalized. They read the full processed signal - including the high frequency boost other decks add but only Dual reads. No more risk of overloading a tape into distortion.
There's still more. Much more. Full metal record and playback. 6-way bias/equalization. Two-motor, twin-capstan drive system.
Computer logic solenoid-activated controls. Switchable multiplex filter. Switchable limiter. Line/mic mixing. Two-way memory stop with automatic replay. Headphone level controls. And operation by external timer or optional wireless remote control.
What about the 839's audible performance? The specifications can give you a hint. Wow and flutter ±0,3 percent WRMS. Frequency Response from 20 Hz to 20 kHz, ±3 dB. Signal-to-Noise  is better than 69 dB
Specifications
Type:  Single cassette tape deck
Track System:  4 Tarack, 2 Channel Stereo
Heads:  1 for Record/Playback;  2 for Erase
Tape Speed:  4,75 cm/s
Pitch:  Control range ±4%
Wow and Flutter :  ±0.03% (WRMS)
To DIN, playback only :  ±0,06%
To DIN, recording/plauback :  ±0,09%
Frequency Response  9ref. To DIN tolerances):
Standard Fe Tape :  30 - 18,000 Hz
CrO₂ Tape :  30 - 19,000 Hz
FeCr Tape :  30 - 19,000 Hz
Pure Metal Tape :  30 - 20,000 Hz
Signal-to-Noise Ratio (with Dolby NR)
Fe Tape : 64 dB
CrO₂  Tape :  64 dB
FeCr Tape :  67 dB
Metal :  67 dB
Channel Separation 9at 1000 Hz)
Between Stereo Channels :  35 dB
Between Channels (in opposite direction) :  60 dB
Erasure (at 1000 Hz):  70 dB
Oscillator Frequency (push/pull oscillator):  105 kHz
Inputs Sensitivity/Impedance:
Microphone Jack :  0,25 mV/10 k Ω
Amplifier/Receiver DIN Jack :  0,5 mV/6,3 k Ω
Amplifier/Receiver RCA Jack :  40 mV/82 k Ω
Outputs Load/Impedance
Amplifier/Receiver DIN Jack :  0-580 mV/10 k Ω
Amplifier/Receiver RCA Jack :  0-580 mV/2 k Ω
Headphones Jack :  4 - 2000 Ω
Fast Wind Time (C-60 cassette):  65 sec.
Line Voltage:  115 volt and 230 volt
Line Frequency:  50/60 Hz
Power Conssumption:  40 W
Dimensions (W x H x D):  440 x 150 x 360 mm

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