> I'm looking for a portable MD player (+/- recorder) with both
> LP modes -and- and very good DAC. I think the DAC in my Sony MZ-R50 is holding
> back the fidelity of the music (based on tests along the lines Francis was
> suggesting).
"Portable" and "very good DAC" are mutually exclusive for technical reasons. In
portable
electronic devices, low power consumption is the *primary* design issue since it must
at
relatively low voltages and currents to get reasonable battery life without having a
huge
battery pack. Very good DACs and analog stages require higher voltage and current than
is avaiable from batteries. Many home CD/MD players use bipolar 5 voltage power for
the
analog section. Better home stereo equipment uses bipolar 15 volt or even 24 volt
supplies.
Also, to get the lowest noise, low impedence circuits, requiring high current are
used. None
of this stuff is possible in a battery powered portable device.
Another consideration is interstage coupling capacitors. To get good low frequency
amplitude
and phase response, large value capacitors must be used. These are often physically
too
large for a poratable unit. Of course, the best approach is to use DC coupling with
servo
amplifiers to cancel the offset, but only very esoteric audio equipment implements the
complex
circuitry required to pull this off sucessfully.
My recomendation, if you want a very good DAC, is to use an outboard DAC where all of
the
power parameters have been optimized for the best audio performance. The built in DACs
in many CD/MD decks, while better than portables, are no match for esoteric, high-end
outboard DACs.
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