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

Akai CD-D1 cd player

The CD player Akai CD-D1 -

Incorporates a large number of well designed ergonomic features. One feature that  particularly liked is that the disc holder is manually closed rather than electronically closed; this relies on the natural response of most users to "push the darn thing closed" and not to look for another switch with which to close it. In the centre of the panel is the display module which is divided into four horizontal layers. The top layer provides mode information, telling you whether the unit is in standby, pause or play mode. The second level of the digital display tells you the number of the selection that is actually playing. If the unit is not playing a zero is displayed. The third row provides the elapsed playing time in minutes and seconds. The programming keys on the right hand side of the panel also tell you the time in minutes and seconds at which the start of a cycle or sequence should commence. The bottom section is a quasi -analogue display which shows the position of the recording head using an array of light emitting diodes. The control switches consist of one double sized 'play' button with its own self indicating LED. four buttons for 'Stop - Eject', 'Pause', 'Fast Forward' and 'Fast Rewind' and two buttons labelled 'PLS' for automatic location of either the previous selection or next selection on the disc.


On the right hand side of the console are ten keys for keying in numerical data, a 'set' switch, a 'cancel' switch and six elongated keys. The top elongated key is for the selection of 'phrase', a term commonly used by all the manufacturers meaning the selection of the time or section in seconds.

The 'index control' is used on those compact discs that have the display IN:DEX. These discs, which are not currently available, will allow you to select the music sequence number and select a particular segment within that sequence. This is achieved by selectively pressing the 'index' key then pressing the sequence number. As none of the discs that I was playing had the IN:DEX display I could not check this function. The 'time' switch tells you the residual playing time on the disc, the 'memo call' allows you to check what you have stored as memory instructions, the 'repeat' switch allows you to repeat one sequence over and over again and the 'total time' switch tells you the total time on the disc. On the back of the unit is a volume control with which you can adjust the player's output level to match your amplifier's auxiliary input requirements. This unit also has a pair of gold plated phono sockets which is a common feature on all the CD players reviewed.

The performance characteristics of the Akaí player are excellent. The frequency response is ±0.2 dB from 20 Hz to 20 kHz and the replay linearity is almost perfect from 0 dB to -60 dB, 0.5 dB high at -80 dB and 1.4 dB high at -90 dB. The A -weighted signal-to-noise ratio both with and without emphasis is 106,4 dB  which is significantly better than claimed for the unit by Akai.  The channel separation from right to left is better than 103,9 dB at 100 Hz, better than -95 dB at 1 kHz, better than -89 dB at 10 kHz and better than  -92 dB at 20 kHz.


The distortion levels at 0 dB are 0,0034% at 100 Hz, 0,0021% at 1 kHz and 0,0027% at 10 kHz.

The distortion level increases as the signal level decreases, so that at -80 dB (reference 0 dB level) the distortion level is 12%. This was just about the highest level of distortion recorded from any machine, although I must make it clear that these distortion levels would be totally inaudible and during the subjective testing we could not detect them. Functionally, the performance of the Akai CD -D1 could not be faulted and I really liked the neat control format and the multiple design features. The best demonstration discs produced a scintillating sound which impressed everybody who heard it.



Disc :

Scanning Velocity:  1,2 - 1,4 m/s

Revolution:  Counterclockwise (viewed from pick-up side)

Track Pitch:  1,6 microns

Disc Diameter/Thickness:  120 mm / 1,2 mm

Signal Format:

Quantization:  16 bit linear/channel (2's Complement )

Sampling Frequency:  44,1 kHz

Channel Modulation Code:  E.F.M.

Channel Bit Rate:  4,3218 Mb/s

Error Correction:  CIRC

Frequency Response:  20 Hz - 20 kHz ±0,5 bd

Signal-to-Noise Ratio: more than 90 dB

Dynamic Range:  more than 90 dB

Channel Separation:  more than 90 dB

Harmonic Distortion:  less than 0,005%

Wow and Flutter:  Quartz Accuracy

Output Level:  2,0 V RMS (100% mod.)

Play / Start Time:  approx. 2 seconds

F.FWD / F. REW Time:  approx. 4 seconds

Random Access Time:  average 3 seconds

Power Requirements:  120 V, 220 - 240 V 50/60 Hz

Dimenisons (W x H x D):  440 x 145 x 320 mm (17,3" x 5,7" x 12,6")

Weight:  7,4 kg (16,3 lbs)

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