CD Transport Rumble

[J.B. Wood]

Does anyone know what might cause an audio CD transport mechanism to to
issue a rumbling noise when playing a commercial CD? I've got beaucoup
commercial CDs (mostly classical) in my collection and I've noticed this
only on one CD (in this case a Philips label), even though it otherwise
plays OK in the CD player. That CD doesn't appear to be warped or
abnormal upon visual inspection. Thanks for your time and comment.
Sincerely,
--
J. B. Wood e-mail: arl_1...@hotmail.com

[Jeff Liebermann]

Off balance CD. I've had it happen when someone attached a stick-on
label to a CD. At high RPM's, the CD will vibrate. I've also seen a
damaged hole in the CD cause the drive clamping mechanism to lock at
an odd angle, also causing vibration. If it's only one CD, try to
make a copy of the CD. If there is something wrong with the CD, the
copy should play normally.

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Dave Platt]

>Does anyone know what might cause an audio CD transport mechanism to to
>issue a rumbling noise when playing a commercial CD? I've got beaucoup
>commercial CDs (mostly classical) in my collection and I've noticed this
>only on one CD (in this case a Philips label), even though it otherwise
>plays OK in the CD player. That CD doesn't appear to be warped or
>abnormal upon visual inspection. Thanks for your time and comment.

I've seen a few CDs where the center hole wasn't "to spec". It was
either slightly undersize, or had bits of plastic "burr" on the edges
of the hole. As a result it would not drop down on the drive spindle
properly, and the CD would sit at a bit of a slant and would wobble
when spinning.

Going around the inside of the center hole with a small piece of
fine-grit sandpaper, to break off any burrs from the molding/stamping
process, and then cleaning the CD carefully to remove any sanding dust
and grit (rinse under running water) has usually worked out. In cases
where it doesn't, I'd "rip" the CD and burn an exact copy, store the
original and use the copy as a play disc.

[Jon Elson]

I had a CD player that started to do something like this. Passages with
only high notes came through well, passages with low notes just dissolved
into something that could be called a rumble. It was odd, the beginning of
the CD played perfectly, at the end the audio was totally inaudible. It was
not a time thing, you could skip to the end of the CD and it would
immediately be bad, skip to the beginning and it was fine.

After some poking I discovered the (brush) motor was shot, there were spots
where the motor would not start.

I just replaced the whole player, it was quite old. But, it was a very
interesting defect that I still don't understand. CDs start at the middle
and spin fast, then slow down as they work out toward the edge. Motor speed
seemed to have something to do with the problem.

Jon

[Jon Elson]

And, reading the thread again, maybe the OP was talking about audible noise
from the transport, not noise in the audio output, which was what I was
thinking at first.

Jon

[olds...@tubes.com]

On Mon, 15 May 2017 13:58:52 -0500, Jon Elson <jme...@wustl.edu> wrote:

>I had a CD player that started to do something like this. Passages with
>only high notes came through well, passages with low notes just dissolved
>into something that could be called a rumble. It was odd, the beginning of
>the CD played perfectly, at the end the audio was totally inaudible. It was
>not a time thing, you could skip to the end of the CD and it would
>immediately be bad, skip to the beginning and it was fine.

I had a cheap CD player (boombox) that only played the first 3 or 4
songs on any CD. It was not worth sticking money or time into it. I put
it in the barn for a barn radio (the radio worked fine). And bought
another CD player.

I think the OP was talking about the CD itself making noise, not the
sound from the speakers. He said it's classical music. If it was rock
music, he probably would not even hear that noise. But I do wonder if
the center hole is not exactly centered. I'm sure that could happen....

[J.B. Wood]

On 05/16/2017 02:35 AM, olds...@tubes.com wrote:

> I think the OP was talking about the CD itself making noise, not the
> sound from the speakers. He said it's classical music. If it was rock
> music, he probably would not even hear that noise. But I do wonder if
> the center hole is not exactly centered. I'm sure that could happen....
>

Hello, and thanks to all who responded. I took a closer look at that
problem CD and indeed the center hole is off center. Not much but
ostensibly enough to elicit the observed effect in the CD player.

[tabb...@gmail.com]

Higher speeds are less affected by motor dead spots, at low speed it would see much more rotational speed variation.


NT

[Jon Elson]

tabb...@gmail.com wrote:

It was odd, the beginning
>> of
>> the CD played perfectly, at the end the audio was totally inaudible. It
>> was not a time thing, you could skip to the end of the CD and it would
>> immediately be bad, skip to the beginning and it was fine.
>>

>

> Higher speeds are less affected by motor dead spots, at low speed it would
> see much more rotational speed variation.
>
>
> NT

Yup. I knew what an interpolation sounded like on that player, a little
chirp when a block of data would not error-correct. This was different, but
maybe the player's chip set had some different method of covering up buffer
errors that tried to fake the data. And, I could easily see at the lower
speed that it could get lots of buffering errors if the speed was unstable.

Jon

[olds...@tubes.com]

On Tue, 16 May 2017 06:27:49 -0400, "J.B. Wood" <arl_1...@hotmail.com>
wrote:

Yep, I had that feeling.....
The result of mass production....

Make a copy of it, and play the copy from now on. I'd copy at the
slowest possible speed because of that "wobble".