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





B&W DM 330i


Bowers and Wilkins DM330i
Stand-mount/Bookshelf loudspeaker system
Product Summary
The DM330i is a 2 1/2-way closed-box stand mount/bookshelf loudspeaker system.
Super sensitive, with high acoustical output yet affordable.
Technical highlights
Modal analysis techniques revealed a simple bonding technique of corner joints could improve rigidity and reduce coloration.
New thinking on crossover design has also led to the provision of higher safe power handling and fuse protection overload.
The driver chassis have non-magnetised castings for all the bass midrange units ensuring resonance free high-level sound of the highest amplitude.

Specifications:
Drive Units:
1 x 26 mm high-frequency driver with dome/coil construction of special polymide material
2 x 200 mm nominal piston dia and 26mm high temperature voice coil with critically impregnated composite short fibre cone
Frequency Response:   48 Hz to 20 kHz (± 3dB)
Sensitivity:  91 dB spl (2.83V, 1m)
Power Handling:  10W – 100W
Dimensions (H x W xD):  857 X 290x 320 mm
Finish:  American Walnut or Black Ash vinyl

Dual C809


Specifications:
The Dual C809 fulfills or exceeds the requirement of DIN 45 500 for domestic HiFi equipment. 
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 ±0,12%
To DIN for recording/reproduction :  less than ±0,16%
Frequency Response (ref-to DIN tolerances)
Fe Standard Tape :  20 -15,000 Hz
CrO₂ Tape :  20 - 15,000 Hz
FeCr Tape :  20 - 16,000 Hz
Distortion K3 at 333 Hz (ref.to 0 dB VU)
Fe Standard Tape :  less than 0,7 %
CrO₂ Tape :  less than 1,5 %
FeCr Tape :  less than 0,7 %
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 56 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 70 dB
Erasure at 1000 Hz :  better than 70 dB
Oscillator (push-pull oscillator):  80 kHz
Inputs ( Sensitivity at 0 dB VU)
Microphone :  0,2 mV/10 k Ω
Receiver/Amplifier
DIN Connector :  0,6 mV/10 k Ω
RCA Jack :  65 mV/ 45 k Ω
Outputs
Receiver/Amplifier
DIN Connector :  560 mV/8 k Ω
RCA Jack :  580 mV/1,0 k Ω
Headphones :  4 - 2000  Ω adjustable
Tape Motion Monitoring:  Electronic
Complement:  2 Ics; 30 Transistors; 13 Diodes; 2 LED's; Z-diode; 1 Silicon bridge rectifies; 2 G-Fuses 400 mA slow-blow
Power Requirements:  100 -125 V / 220 - 240 V, 50/60 Hz
Power Consumption:  approx. 10 Watt

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