Sony MDS-JE440 Manual Do Utilizador

http://www.sel. sony.com/SEL/rmeg/
mediatech/techspec/techMD.html.

Conventional MO recorders employ

a fixed magnetic field, switching the
laser beam on and off. With this sys-
tem, a portion of the disc must be com-
pletely erased before you can record
on it. This requires separate erase and
record passes, doubling the time it
takes to make a recording, or separate
erase and record lasers, which signifi-
cantly increase the complexity and the
cost. The MiniDisc overcomes this
problem by keeping the laser beam
constant and varying the magnetic
field. 

In playback, a low-level laser beam is
used, one that does not heat the disc.

The changes in magnetic polarity
cause the polarization angle of the re-
flected light to change. Pre-recorded
MiniDiscs are manufactured using a
molding process, but the reflections
from the molded surface are compati-
ble with the MiniDisc’s laser pickup.
All MiniDisc players are designed to
play both pre-recorded and recordable
MiniDiscs. 

HHB, manufacturer of some of the

finest professional CD and MiniDisc
recorders and media available, has pub-
lished an excellent guide to the various
current digital recording formats. This
document is available for download in
.PDF format. Go to http://www.hhb.co.
uk/usa.htm, and click on “Brochures,
Manuals and Ads,” then click on
“Brochures.” Look for “A Guide to

Choosing and Using Digital Audio
Recording Media.” 

Photo 2 shows a Sony Premium Gold

MiniDisc, which is housed in a small
plastic cartridge measuring only 2 

¹³₁₆

×

2 

¹¹₁₆

″

. These premium MiniDiscs are

manufactured with a shock-absorbing
mechanism that reduces the transmis-
sion of vibrations made by the recorder
or player to the disc itself. They are
available five to a pack for around $15 in
retail stores. Sony and several other
manufacturers make cheaper media for
less critical applications.

Photo 3 shows the inside of the MDS-
JE440. Nearly all of the circuitry is con-
tained in proprietary Sony surface-
mount integrated circuits. The A/D and
D/A converters use Sony’s Wide Bit
Stream technology. The A/D converters
are 24-bit, and the Hybrid Pulse D/A
converter operates in conjunction with
an 8

×

oversampling digital filter. 

Surface-mount IC op amps are used

for the analog amplification circuitry.
My unit was supplied with 4570 types—
these are not listed on the NJR 
website, but it is probably safe to as-
sume that they are superior to the
usual 5532 or 4558 types still found 
in some consumer gear. The MDS-
JE440 contains a conventional (i.e.,
non-switching) power supply. 

Photo 4 is a close-up of the mecha-

nism. The laser assembly faces upward,
toward the bottom of the MiniDisc. The
magnet assembly is located above the
laser assembly. 

Photo 5 shows the same close-up

with a MiniDisc inserted, and the play-

audioXpress  October 2001 75