P
Phil Allison
Guest
Hi to all,
A friend showed me his new personal CD player bought from Tandy yesterday -
an Aistar for $30. Comes with headphones and has 60 seconds of "anti shock"
and also as "bass boost" switch. Stick in a CD, pop on the phones and voila
music - but something sounded not right.
Tried some better grade phones ( same 32 ohm impedance) and the sound was
actually worse - fuzzy, edgy in an odd way. OK - so off to the test
bench and tried my Denon test CD and the *line output* viewed on a CRO.
A 1001 kHz test tone looked a bit furry - probably some HF residual in the
supersonic range, I though.
A 100 Hz square was almost perfect.
3150 Hz and 9999Hz test tone looked furrier than the 1001 Hz tone.
** OK - now back to the headphones and simply listening:
The 1001 Hz tone was furry because of wide band noise (hiss) - very audible
at maybe 30 dB below the tone.
The 9999 Hz tone sounded like several high frequency tones at once - bit
like a nail being scraped on a sheet of metal - plus the aforementioned
hissing noise.
BTW All the sine wave tones on the Denon CD are precision, 16 bit
digitally generated so test and sound perfect on a normal home CD player or
DVD player.
Some solo piano music was then tried on the Aistra and sounded just awful -
with a rough distortion like that from a worn stylus playing a worn and
noisy LP. This machine carries the usual Compact Disc Digital Audio logo -
but the makers obviously threw the Red Book standard right out the damn
window !!!!
My best hunch is that in order to make the 60 second "anti shock" music
memory cheap - not all 16 bits of each audio sample are stored but maybe
only 6 or 8 of them. This would cut 10.6MB of storage otherwise needed down
to 5.3 MB or less - plus explain the high noise levels.
Other DSP tricks maybe involved too of course.
The unit came with no specs whatever - a bad sign I suppose !
Are there similar units that have normal CD player performance ??
What do they cost ??
.............. Phil
A friend showed me his new personal CD player bought from Tandy yesterday -
an Aistar for $30. Comes with headphones and has 60 seconds of "anti shock"
and also as "bass boost" switch. Stick in a CD, pop on the phones and voila
music - but something sounded not right.
Tried some better grade phones ( same 32 ohm impedance) and the sound was
actually worse - fuzzy, edgy in an odd way. OK - so off to the test
bench and tried my Denon test CD and the *line output* viewed on a CRO.
A 1001 kHz test tone looked a bit furry - probably some HF residual in the
supersonic range, I though.
A 100 Hz square was almost perfect.
3150 Hz and 9999Hz test tone looked furrier than the 1001 Hz tone.
** OK - now back to the headphones and simply listening:
The 1001 Hz tone was furry because of wide band noise (hiss) - very audible
at maybe 30 dB below the tone.
The 9999 Hz tone sounded like several high frequency tones at once - bit
like a nail being scraped on a sheet of metal - plus the aforementioned
hissing noise.
BTW All the sine wave tones on the Denon CD are precision, 16 bit
digitally generated so test and sound perfect on a normal home CD player or
DVD player.
Some solo piano music was then tried on the Aistra and sounded just awful -
with a rough distortion like that from a worn stylus playing a worn and
noisy LP. This machine carries the usual Compact Disc Digital Audio logo -
but the makers obviously threw the Red Book standard right out the damn
window !!!!
My best hunch is that in order to make the 60 second "anti shock" music
memory cheap - not all 16 bits of each audio sample are stored but maybe
only 6 or 8 of them. This would cut 10.6MB of storage otherwise needed down
to 5.3 MB or less - plus explain the high noise levels.
Other DSP tricks maybe involved too of course.
The unit came with no specs whatever - a bad sign I suppose !
Are there similar units that have normal CD player performance ??
What do they cost ??
.............. Phil
