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.

Specifications:
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
Receiver/Amplifier
DIN Connector :  0,45 mV/4,7 k Ω
RCA Jack :  70 mV/ 82 k Ω
Outputs
Receiver/Amplifier
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

I like 

Akai GX 260D


The GX 260D means the machine is fitted with Akai's unique Glass and Crystal Ferrite head. This head is completely unique to Akai. The core of the head is  a "single crystal" gem set in pure glass of terrific hardness. Because the gem set in pure glass of terrific hardness. Because the gem is a single crystal, it has no composite particles that can break off and damage he head. (Inn a way, it's rather similar to the jewel action in a watch - except that Akai would be the only watch - maker to use it.)
So, the head remains wear-free for life. In fact, Akai guarantee it. If the GX head on your Akai machine wears out in normal use during the lifetime of the machine, we will repace it without charge.
And in the meantime, the GX head gives you outstanding performance because the head and the tape are kept in perfect contact at all times - even high frequency distortion is very greatly reduced.

The GX 260D has four heads - 2GX recording/ erase heads and 2 GX playback heads. It features automatic or manual revers for both recording  and playback.
It has 3 motors - one self-lubricating hysteresis synchronous capstan drive motor, two eddy-current outer-rotor reel drive motors. The advantage of the centre capstan drive motor is that it ensuress identical performance in both tape directions.
The GX 260D offers you line output  level control. It lets you add echo effect to any recording. And, of course, it has all the facilities for sound-on-sound, sound-with-sound, and microphaone/line mixing.
There's also a yape/Source montor,  a Tape Selector Switch and Automatic  shut-off.

Specifications:
Track System:  4-track, 2-channel stereo/monaural
Reel Capacity:  up to 7" reel
Tape Speed:  7-1/2 and 3-3/4 ips
Wow and Fluter:  less than 0,06% WRMS at 7-1/2 ips; less than 0,1% WRMS at 3-3/4 ips
Frequency Response: 
Low Noise Tape :
30 - 26,000 Hz (±3 dB) at 7-1/2 ips
30 - 20,000 Hz (±3 dB) at 3-3/4 ips
Regular Tape :
30 - 23,000 Hz (±3 dB) at 7-1/2 ips
30 - 18,000 Hz (±3 dB) at 3-3/4 ips
Distortion:  less than 1,2% (1,000 Hz, 0 VU)
Signal-to-Noise Ratio:
Activated Tape Selector Circuit :  Better than 57 dB
Inactivated tape Selector Circuit :  Better than 54 dB
Erase Ratio Cross-Talk:
Mono :  better than 60 dB
Stereo :  better than 45 dB
Bias Frequency:  100 kHz
Heads:  two GX recording/erase combination heads, two GX playback heads
Motors: 
One :   4/8-pole self-lubricating hysteresis synchronuous capstan drive motor;
Two :  Eddy-current outer-rotor reel drive motors
Fast Forward / Rewind Time:  75 sec using 1200 ft tape
Output Jacks:
Two Line :  1,23 V, 0 VU/100 Ω (required load impedance more than 20 k Ω)
One Phono :  30 mV/ 8 Ω
Input Jacks:
Two Line :  50 mV
Two Microphone :  0,3 mV/4,7 k Ω
DIN Jack:  0,5 V/25 mV
Power Requirements:  100 V to 240 V AC, 50/60 Hz
Dimensions (W x H x D):  17,5 " x 18,6" x 8,9"
Weight:  45,8 lbs

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.

Specifications:
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
Performance
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)

TEAC A-X5030


Integrated Stereo Amplifier A-X5030
Features:
High-power drive capability
Switchable subsonic filter
-20 dB muting switch
Loudness compensation switch
Center-detented bass and treble tone controls
Balance control
Dual speaker terminals and independent speaker A/B switches
Heavy-duty binding-post speaker terminals
Large insulator feet.

Another example of TEAC dedication to delivering the finest possible quality in these amplifiers is the fact that each unit is individually calibrated for optimum performance.
In the A-X series amplifiers, the output stage idling current is determined by a precision trimmer rather than the usual fixed resistor. This is adjusted to provide optimum idling current - and therefore an absolute minimum of crossover distortion - during the final testing and inspection stage. You can rest assured that the amplifier you receive is fine-tuned to deliver super sound quality.
All-Mechanical Short-Path Signal Switching
Many modern amplifiers use semiconductor switches to control signal routing. These like any other electronic part, can degrade signal quality. TEAC has used only top-quality mechanical switches ensuring reliable, distortion-free signal routing. Furthermore, switches handling low level signals are positioned as close as possible to the corresponding rear-panel terminals to minimize the signal path length and are remotely controlled via the panel knobs. This means that noise and interference pickup is minimized for extra signal purity.
 Source Direct Switch
When you want an extra margin of signal purity, the Source Direct switch can be engaged to bypass the tone, balance, loudness controls, muting and subsonic filter controls, giving you the shortest, most direct signal path possible for all input sources.
Versatile Input and recording Capability
Independent input and Rec selectors let you monitor one source while simultaneously recording another. The Rec selector also offers tape-to-tape recording capability. The A-X5030 accept of 6 base input sources like; phono, tuner, CD, tape 1/DAT, tape 2, AUX, and additionally features Adapter/Tape 3 terminals that can be used to connect a third tape deck or an external adapter such as a graphic equalizer or surround processor. The A-X5030 also features a high-performance internal MC phono cartridge head amplifier and an MM/MC phono selector switch.
Heavy-Duty Binding-Post Speaker Terminals
Since speaker cables can have a significant effect on the sound, the TEAC amplifiers are equipped with heavy-duty binding-post terminals that will easily accept high-quality speaker cables while providing solid reliable contact.

Specifications:
Continuous Power Output (RMS):
At 8  :  75 W + 75 W (20 - 20,000 Hz, 0,02% THD)
At 4  :  100 W + 100 W (20 - 20,000 Hz , 0,04% THD)
DIN Power Output:
At 8  :  85 W + 85 W (1 kHz)
At 4  :  120 W + 120 W (1 kHz)
Dynamic Power Output:
At 8  :  100 W + 100 W
At 4  :  150 W + 150 W
Total Harmonic Distortion (Continuous Rated Output Power):
At 8  :  0,007% (1 kHz)
At 4  :  0,01 % (1 kHz)
Input Sensitivity/Impedance:
Phono (MM) :  2,5 mV/ 47 k Ω
Phono (MC) :  0,25 mV/100 Ω
CD, Tuner, Aux, Tape :  150 mV/30 k Ω
Signal-to-Noise Ratio (IHF--A):
Phono (MM) :  80 dB (5 mV)
Phono (MC) :  67 dB (0,5 mV)
CD, Tuner, Aux, Tape :  101 dB
Frequency Response:
Phono (RIAA) :  20 - 20,000 Hz ±0,5 dB
CD, Tuner, Aux, Tape :  5 - 100,000 Hz -3 dB
Dimensions (wxhxd):  435 x 155 x 354 mm
Weight:  10,5 kg