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 C 939

The more experience you've had with tape decks, the more you're likely to appreciate the Dual C939's performance and versatility. Apply the most demanding musical tests; sustained piano tones for flutter; extreme highs and lowes for frequency response; soft passages for Signal-to-Noise ratio - and you will hear no diference between the original disc and tape made on the 939. all of which brings to life the 939's impressive specifications for wow and flutter (0,05%), Signal-to-Noise (65 dB) and frequency response (20-17,000 Hz). Now we'd like to take you through the 939's astonishing array of design and operating features.
Auto/reverse playback, bi-directional record. The 939 reverses automatically in play-back - a C-90 will play 90 minutes without interruption. There's continuous play too. Recording is bi-directional. When the tape reaches the end, youu just reverse direction.
With any other deck you either live with unwanted sounds on a tape or erase them abruptly - without hearing what you're doing until it's too late.
With the 939's unique fade/edit control you can fade out those annoyances gradually, smoothly and permanently. And then fade back into the music. While listening. Because it's all done during playback.

Drive system and tapeheads like no other.
Dual's powerful Continuous-Pole /synchronous motor,, two capstans and two drive belts maintain speed accuracy within 0,5% . A C-90 cassette fast-winds in lust over a minute, the time other decks need for a C-60. hard permalloy tapeheads are used for their extended life and superior magnetic linearity. The four-track record/playback head switches electronically when the tape changes direction, it never shifts position. The result; perfect tape alignment in both directions at all times.

LED Record-Level Indicators
Meter needles can't move fast enough to keep up with musical signals. Which is why the 939 uses instantaneous reacting LED record-level indicators. And they lilt to the best viewing angle.

The Dual C939 meets or exceeds the requirement of DIN 45 500 for domestic HiFi equipment. The data given base upon the current DIN reference tapes.
Tape Speed:  4,75 cm/s
Deviation from Correct Speed:  less than ±1%
Wow and Flutter:  weighted RMS :  less than ±0,07%
To DIN for reproduction only :  less than ±0,10%
To DIN for recording/reproduction :  less than ±0,10%
Frequency Response (ref-to DIN tolerances)
Fe Standard Tape :  20 -14,000 Hz
CrO₂ Tape :  20 - 16,000 Hz
FeCr Tape :  20 - 17,000 Hz
Distortion K3 at 333 Hz (ref.to 0 dB VU)
Fe Standard Tape :  less than 1,2 %
CrO₂ Tape :  less than 1,8 %
FeCr Tape :  less than 1,0 %
Signal-to-Noise Ratio (weighted)
With Dolby NR
Fe  Tape : better than 63 dB
CrO₂ Tape : better than 63 dB
FeCr Tape : better than 65 dB
Without Dolby NR
Fe Tape :  better than 53 dB
CrO₂ Tape : better than 56 dB
FeCr Tape :  better than 58 dB
Channell Separation at 1000 Hz
Between Stereo Channels :  better than 30 dB
In Oppositie Direction :  better than 60 dB
Erasure at 1000 Hz
Fe Tape :  better than 70 dB
CrO₂ Tape : better than 65 dB
FeCr Tape :  better than 70 dB
Oscillator (push-pull oscillator):  80 Hz
Inputs ( Sensitivity at 0 dB VU)
Microphone :  0,30 mV/10 k hm
DIN Connector :  0,45 mV/4,7 k Ω
RCA Jack :  70 mV/ 82 k Ω
DIN Connector :  0 -700 mV/1,8 k Ω
RCA Jack :  0 - 700 mV/1,8 k Ω
Headphones :  4 - 2000 k Ω adjustable
Fast Winding:  C-60 less than 60 sec.
Complement:  4 Ics; 49 Transistors; 30 Diodes; 1 Darlington photo cell; 28 LED's
Power Requirements:  100 -125 V / 220 - 240 V, 50/60 Hz
Power Consumption:  approx. 35 VA

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