Questions on CD players

Archived from groups: rec.audio.tech (More info?)

(Comments inserted)

"Michael McKelvy" <deskst49@peoplepc.com> wrote in message
news:62u0d.1003$az6.588@newsread2.news.atl.earthlink.net...
> 1. Is there any reason to believe that certain kinds of feet on a CD
> player will make it less susceptible to vibration? In a stand alone CD
> player is vibration even a problem?

A properly designed dc player shows little effect from small vibrations.
Many cheaper changers etc are worse about this. You can try lightly tapping
on the case while playing a disc, or pounding somewhat harder on the table
beside the player, gradually increasing, and at some point the player will
probably skip. At a lesser level, if one uses an oscilloscope to view the
tracking or focus error waveforms at the test points inside the unit, it is
obvious that external vibrations do affect the pickup while playing. I can
even SHOUT at the pickup and see the waveform of my voice superimposed. This
is because of the way pickups are designed, much like a speaker voice-coil.
This is rarely a problem, but I'm all for eliminating as much of this as
practical for technical reasons.

>
> 2. Error correction, does it correct all errors on a normal readable
> disk?
>

Yes. Even in fairly extreme cases, when not corrected, the errors are
concealed. Much worse and the player will stop, stutter, skip, etc.

> 3. Has there ever really been a problem with audible jitter in consumer
> players?
>

A matter of debate for audiophiles, but rarely if ever audible.

> TIA
>

You're welcome.


Mark Z.

Archived from groups: rec.audio.tech (More info?)

On Sat, 11 Sep 2004 03:12:02 GMT, "Michael McKelvy"
<deskst49@peoplepc.com> wrote:

>1. Is there any reason to believe that certain kinds of feet on a CD player
>will make it less susceptible to vibration? In a stand alone CD player is
>vibration even a problem?

Yes, but OTOH no, in that order.

>2. Error correction, does it correct all errors on a normal readable disk?

No, you'll typically get one sub-millisecond 'best guess'
interpolation every five minutes, and less than one 'mute' error per
CD, otherwise data recovery is *perfect*. Do you think that kind of
error level is audible?

>3. Has there ever really been a problem with audible jitter in consumer
>players?

That's a vexed question, but probaly not, with the possible exception
of some exotic 'high end' designs. The only noticeable pattern with
'high end' designs (aside from ludicrous pricing) is that this is
where you'll find the *really* incompetent designs.......
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Archived from groups: rec.audio.tech (More info?)

On Sun, 12 Sep 2004 10:17:31 GMT, "Michael McKelvy"
<deskst49@peoplepc.com> wrote:

>
>"Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
>news:na76k09qvk5flqumh0jog90a0pkcj54nps@4ax.com...
>> On Sat, 11 Sep 2004 03:12:02 GMT, "Michael McKelvy"
>> <deskst49@peoplepc.com> wrote:

>>>3. Has there ever really been a problem with audible jitter in consumer
>>>players?
>>
>> That's a vexed question, but probaly not, with the possible exception
>> of some exotic 'high end' designs. The only noticeable pattern with
>> 'high end' designs (aside from ludicrous pricing) is that this is
>> where you'll find the *really* incompetent designs.......
>> --
>Why am I not surpised? Only the "high end" would put a $100.00 cd player in
>a $500.00 cabinet and claim it was to improve problems with vibrations.

Mark Levinson put a $50 'CD jukebox' mechanism in a $10,000 cabinet,
and make all kinds of technobabble claims for it................

--

Stewart Pinkerton | Music is Art - Audio is Engineering

Archived from groups: rec.audio.tech (More info?)

"Stewart Pinkerton" wrote ...
> On Sat, 11 Sep 2004 03:12:02 GMT, "Michael McKelvy"
> <deskst49@peoplepc.com> wrote:
>
> >1. Is there any reason to believe that certain kinds of feet on a CD
player
> >will make it less susceptible to vibration? In a stand alone CD player
is
> >vibration even a problem?
>
> Yes, but OTOH no, in that order.
>
> >2. Error correction, does it correct all errors on a normal readable
disk?
>
> No, you'll typically get one sub-millisecond 'best guess'
> interpolation every five minutes, and less than one 'mute' error per
> CD, otherwise data recovery is *perfect*.

Note that "Red-Book" audio CDs have much looser error-correction
than the "Yellow-Book" format used for data CDs (which actually is
"perfect" ) after error correction.

> Do you think that kind of error level is audible?

I don't, but then my ears are only flesh-colored.
They're not even tin-color, much less *golden*. :-)

Archived from groups: rec.audio.tech (More info?)

On Sun, 12 Sep 2004 08:12:24 -0700, "Richard Crowley"
<rcrowley7@xprt.net> wrote:

>"Stewart Pinkerton" wrote ...
>> Mark Levinson put a $50 'CD jukebox' mechanism in a $10,000
>> cabinet, and make all kinds of technobabble claims for it...........
>
>But surely the quality of their ones and zeroes are superior? :-)

Well, of course! Ones are guaranteed to be between 0.9999999 and
1.000001, while zeroes are between 0 and 0.000001. Of course, the
receiver is perfectly happy if ones are between 0.67 and 1.5, and
zeroes are between 0 and 0.3, but that doesn't sell the 'high-end
magic', now does it? :-)

BTW, in case anyone wonders, the above was a joke, in that ML don't
actually guarantee that their digital datastream is better than that
of the cheapest Magnavox portable player. Because they couldn't, since
both use the same basic reading mechanism.............
--

Stewart Pinkerton | Music is Art - Audio is Engineering