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





Ampex ATR-700

 When you introduce a new model to succeed the most respected line of portable recorders in audio history, it had better be something special. It must be more than a new recorder  - it must be a significant improvement, ATR-700 is both.
For more than 20 years, Ampex 500 and 600 series recorders have distinguished themselves under the most demanding conditions. Long regarded as the professional's choice for reliability in the field, their reputationfor ruggedness and performance has made them the standard of excellence by which other portable recorders are measured. Through the years, progressive generations of these solid machines have proved themselves around the world and in every conceivable professional application, from on-location sound recording for motion pictures to studio recording and on-the-air broadcasting.

ATR-700 for the audio pro who needs a recorder he can trust or the institution demanding professional performance.
Here's a machine with concert hall quality in a road show package. It fils the need for more versatility and built-in convenience with many standard features that either aren't available or cost extra on other compact recorders. It's a professional in every respect - as a portable broadcast recorder, editing recorder, or remote recorder.
 Every ATR-700 includes 2-channel electronics. So, if you order a single-track machine and develop requirements for 2-channel capability, simply plug in the appropriate heads. Head stacks are precision manufactured and offer plug-in flexibility to permit individual replacement and configuration changes. And they're located for easy access, too.
The capstan servo D.C. motor is of the direct drive type, providing the advantages of greater torque with improved operational control and speed accuracy.
Pick the speed pair that best suits your needs 3¾ and7 ½ or 7½ and 15 ips. No matter which version you choose, you get added flexibility and command with the built-in variable speed control.
A universal power supply makes the ATR-700 truly cosmopolitan. A voltage selector permits operation on AC power anywhere in the world. The optional portable case lets you take it with you - or use the rack mount adapter for easy installation in standard 19-inch racks. Precision operation is assured in both vertical and horizontal positions.
 Electronic motion sensing affords safe and rapid transition between operating modes. You can move from shuttle speeds to playback and cice versa without touching the stop button.
Synchronous reproduce is standard. This feature lets you record a second channel in sync with the sound on the forst channel.
Automatic shut-off is actuated by the tape tension arm, and a cue control permits manual defeat of one of the automatic tape lifters for monitoring at shuttle speeds.
Separate switches are located on the front panel for bias, equalization and reference level, so you can maximize performance with the professional tape of your choice. An edit button permits spilling tape in playback to simplify editing operation.
Three reel sizes can be used with the ATR-700, and the front panel reel selector gives proper tension  for  5" / 7" and 10½" reels
 Additional features help to make ide easier, such as non-glare, back-lighted VU meters, balanced mic input with switchable 20 dB attenuator, and a bult-in 4-in, 2-out mixer with master gain control. A pause  button provides added cueing flexibility and quickstarts, while the pinch roler automatically swings away when in "stop" mode to allow easy threading. Modular design with plug-in PWA's permits ready acces to vital electronics and greatly simplifies mintenance. For extra convenience, an extender board with integral test points is included as standard equipment. Designed in versatility also means reliable operation under a wide range of environmental conditions - to meet the needs of users with special requirements or tough field applications. ATR-700 has the personality of a "seasoned pro".
 New versatility.
3 record/reproduce fromats 93-head configuration)
- Full track (1 channel 
- 2-track (2 channel) 
- ¼ track 92 channel)
All versions include 2 channel electronics
Position for a fourth head
Choice of 2 speed pairs
Universal power supply
Separate 3-position switches for biass, equalization, and record level selection
Adjustable pitch range (variable spped control)
NAB/IEC equalization (switchable)

New Convenience
Feather-touch transport controls
Handles 10 ½", 7" and 5" reels
Switchable reel size (tension) selector
Tape lifter defeat lever (cue control)
Edit button for dump edit in play mode
Rapid-response electronic motion sensing
3 mounting configurations
Fully remotable, electronically controlled transport
Professional XLR input/ouutput connectors
4-digit tape counter with rewind-stop memory

Improved Performance
3-motor tape drive system with capstan-servo D.C. motor
Synchronous reproduce system improved over-all performance for frequency response. S/N, crosstalk, flutter and wow, erasure depth
Full IC logic circuitry
End of tape auto shut-off (tension arm actuated)
Specifications
Tape Speed:  Switchable two speeds; 3¾ and 7½ in/s  or 7½ and 15 in/s. adjustable pitch range ±5%
Reel Sizes:  5", 7" and 10½" per ANSI and NAB standards
Reel Hub Size Selector:  2 positions; large or Small reel hubs
Tape Width:  ¼"
TapeSpeed Accuracy:  Within ±0,3% at both speds
Wow and Flutter (weighting is NAB measured by the reproduce method):
0,08% WRMS at 7½ and 15 in/s
0,12% WRMS at 3¾ in/s
Shuttle Time:  approx. 90 sec. For 1200-foot reel in either direction
Tape Drive System:  Three-motor direct drive
Capstan Motor:  DC servo motor, direct drive
Head Configuration:  3 heads for erase, record and reproduce,
1-track 1-channel ( has basic 2-channel electronics);
2-tracks 2-channel
¼-track 2-channel.
Tape Timer (accuracy is within ±10% max error): max 99 minutes and 59 seconds (for higher speed)
Line Output:  +4 dBm, 600 Ω, balanced (can be set up for +8 dBm)
Max. Line Input:  =24 dBm
Line Input:  -10 dB (0 dB = 0,775 V), 100 k, unbalanced
Mic Input:  -70 dB (0 dB = 0,775 V), 600 Ω, balanced with switchable;  -20 dB attenuator
Max. Mic Inputs (attenuator Off):  -30 dB (0 dB = 0,775 V)
Input Connector:  Cannon XLR-3-31
Output Connector: Cannon XLR-3-32
Equalization:  NAB or IEC switchable or rear panel
Record/reproduce Frequency Response:
15 in/s :  40 Hz - 100 Hz ±3 dB and 100 Hz - 18 kHz ±2 dB
7½ 1n/s :  40 Hz - 100 Hz +3-2db and 100 Hz - 15 kHz ±2 dB
3¾ in/s :  40 Hz - 7,5 kHz ±2 dB
Distortion (THD) maximum:  NAB equalization, 15 in/s
0,3% at 400 Hz , 185 nWb/m
4,0% at 15 dB above 185 nWb/m
Eq/Bias/Level:  Separately switchable for different tapes
Switch Position Rec Eq./ Rec Bias/ Rec level (456, 406, 641 Ampex tape)
3 :  3M250 / 3M250 / 456/3M250 (=6 dB)
2 :  406 / 456/406 / 406 (+3 dB)
1 :  456/641 / 641 / 641 (185 nWb/m 0 dB)
Erasure:  70 dB at 400 Hz  =10 dB reference
Signal-to-Noise Ratio (overall, A weighted):  NAB equalization referred to 6 dB above 185 nWb/m
¼ track :  55 dB
2 track :  60 dB
IEC equalization referred to 329 nWb/m
2 track :  58 dB
Frequency Response For Synchronous Reproduce:
100 Hz - 12 kHz, ±4 dB at 15 in/s
100 Hz - 8 kHz, ±4 dB at 7½ in/s
Synchronous reproduce S/N (overall A weighted):  NAB equalization referred to 6 dB above 185 nWb/m
¼ track :  40 dB
2 track :  45 dB
Headphone Output:  10 k Ω minimum load, unbalanced, standard 3-conductor stereo phone jack =0,8 volt ±2 dB
Record level Calibration, 0 vu=:  0 dB referred to 185 nWb/m of tape flux
Position 1 :  -0db
Position 2 :  +3 dB
Position 3 :  =6 dB
Power Requirements:  100/120/220/240 V ±110%, 50/60 Hz switchabile
Power Consumption:  159 Watts
Dimensions (H x W x D):  548 x 40 x 254 mm (21-5/5" x 17-3/8" x 10-1/6")
Weight:  approx. 28 kg (62 lb)


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