Strange Oscillation


Alright, I need to get to the bottom this. On a couple of CD's at certain passages, the music goes into an oscillation and won't quit until the volume is reduced or the disc stopped entirely. My playback source is an Ayre C-5xeMP, Plinius Tautoro pre and Plinius SA-103 amp. Interestingly this only happens on a few CD's and usually when there is a sustained chord such as from a keyboard note that is held or a sustained vocal. Two examples are Pink Floyd, Dark Side of the Moon, track one about mid point with the EMI Japan release CDP746001 Z. I also have the MFSL issue and it plays with no problem. Another example is Patricia Barber, Cafe Blue standard redbook release during a sustained high pitch vocal note and only at high volume. So what causes this to occur? It is obviously related to the CD itself since DSOTM MFSL issue plays just fine. Can anyone enlighten me?
Convert?fit=crop&h=128&rotate=exif&w=128falconquest
Hmm have you tryed isolating the player just for kicks differently.

oleschool,
I assume you mean from a vibration standpoint. The Ayre sits on a solid maple shelf almost 2" thick and from there is perched upon vibrapods. I really don't  think vibration is the cause but at this point can't rule anything out. What's interesting is that it happens only on certain CD's.
I have Cafe Blue, standard CD and cannot hear any high pitch vocal.  In fact, it is the one of the best recorded CDs used for demo in many stores. Can you point to particular song, minutes, seconds?

Vibrapods might protect CDP from vibrating shelve, but will do the opposite when CDP body vibrates.  Did you try to remove them?

Perhaps laser is weak (dirty).  Try to clean it.
kihanki,
No high pitched vocal? I am referring to the track "Too Rich for my Blood" (one of my favorites) at about 5:19 when Patricia hits that high note. So how does one go about cleaning the laser? I'm certainly open to trying that.
My only reason for saying iso was just a "try it thing" I have a cple cds when I am getting down I get nervous at certain points because they have let loose a serious ocilation in the left driver at dam near the exact time ( not clipping my amp not even close).I always figured i was pushing it too hard and overdriving the driver .But it again happens in a cple select cds .You seem to have iso I still would pull the maple and iso and try it if its not hard.I doubt thats it ,it’s probly in the cd.Do you have another setup or another freind to try it on? Not mine lol ... good luck

Falconquest, I just checked - it is clean. I used high volume on headphones and speakers.  There is a lot of sibilants, more vivid with headphones, but still clean.  5:19 high voice note is very clean.  You could clean laser with laser cleaning CD.  I was suspecting time jitter of digital signal, that converts to noise, but it would shows in unpleasant sibilants first.  I suspect, that you have some system or room resonance at this frequency.  Try to eliminate things.  Is it tweeter?  Is it in both channels?  Can you borrow another CDP or rip it and play it from computer or the phone?  Better yet, can you take this CD to a friend?  
kijanki, I think you are on to something when you mention system or room resonance because that's what it sounds like. It's almost like a feedback loop is occurring. If you think about it, the high pitch frequency output from the speaker may be establishing a resonance inside the CD player but since we're talking about a sound frequency vs. light frequency, I can't imagine they would interact. I get your idea of switching CD players etc. but in essence I have done that by switching out CD's. The MFSL DSOTM CD has no issue while the Redbook CD does. I can crank the volume on the MFSL CD with no problem. It has to be related to the CD itself. I'll try the cleaning idea and report back.
@falconquest Another idea would be to try that specific CD in someone else's system.
Falconquest - much of this thread points to issues unrelated to my comments below, but there are a couple of comments which made me wonder....

I do have first hand experience with a problematic Ayre amplifier and internal osculation issues.

The amp actually blew some internal components and the reason was the speaker cables, which had a sufficiently high capacitance, caused the amp to "oscilate" to a degree that some internal components were overloaded.

The cables in this case were from Cardas - replacing the cables with a pair of a lower capacitance resolved the issue completely.

The amp had previously been working with the Cardas cables, but the introduction of a high quality power cable was just enough to provide enough electrical energy to put it over the top.

The amp is now working perfectly well with the new power cable and a new pair of lower capacitance speaker cables.

BTW, the owner of the amp had also tried the Cardas cables on another high-current design amp and blew that amp also.

This oscillation issue is well documented on the web and effects only those solid state amps of a high current design - Ayre being one of them.

I don't know if this is your problem, but it is pretty easy to rule it out - simply try installing a different speaker cable.

Hope this helps


falconquest,
all good suggestions by other A'gon members. Here's another thing to try - use a black Sharpie to paint the outer rim of the CD (similar concept to using a Stoplight pen). I've done this to some of my favourite music CDs. Since the black line (the width of the Sharpie nib) is along the outer rim where there is no music/data content it will not affect reading the disk. What this black ring on the outer rim does is reduce/eliminate any laser reflection & multiple erroneous pick-up of data during read-back which is one source of distortion.
if it does nothing for you, you can use alcohol & erase this black ring & your CD will be back to its original looks.
Many of my CDs which have a transparent section at the center spindle hole have been colored black using a Sharpie in addition to a black outer ring. It might not make any difference but it helps cut down on laser reflection off the shiny disk. FWIW. YMMV.  
Yes, as Bombaywalla indicated a number of good suggestions have been made. And as the diversity of those suggestions shows, there are a lot of different possibilities that may account for the issue. Some further thoughts:

First, just to be sure, is the MFSL DSOTM truly just a redbook CD, or might it have an SACD layer as well, that may be what has been played without the issue appearing?

Second, given that the problem is both volume sensitive and note sensitive, the only effects I can envision that might be occurring are:

1)The player’s ability to track and/or read the disc is marginal, and vibration may be putting it over the edge when the problematic notes are played at high volume. (I would not assume that the two versions of DSOTM, one of which precipitates the problem and one of which does not, have been mastered identically). Good suggestions have been made above regarding this possibility.

2)Either the power amp or the circuitry in the preamp that is downstream of the volume control may be marginally stable, and certain notes may be putting it over the edge. (Again, I would not assume that the two versions of DSOTM, one of which precipitates the problem and one of which does not, have been mastered identically).

3)The amount of current drawn by the power amp when the problematic notes occur may be affecting the AC line voltage, and that fluctuation in line voltage may be affecting something that is marginal in the system.

Regarding nos. 2 and 3, if I’m not mistaken your power amp can be switched between class A and class AB operation. As an experiment, it may be worth trying it in whichever of those modes you have not been using.

Also, as an experiment it may be worth trying the listen/measure switch that is on the back of the Ayre CDP in whichever position you have not been using.

And it would certainly make sense to try the problematic CDs in the Oppo player you appear to have in your system.

Regarding Williewonka’s suggestion of trying different speaker cables, I agree that the application of excessive load capacitance to the power amp outputs could conceivably be involved. Especially given that your speakers have highly capacitive phase angles at certain frequencies, as well as low impedance. Although it appears from your system description photos that the cable lengths you are using are probably fairly short, which means that the unspecified capacitance of your Morrow cables is probably not especially high. In any event, as an experiment you could reduce the capacitance the cables present to the amp by a factor of two by disconnecting one of the two biwire runs, insulating the disconnected exposed terminations, and using jumpers on the speaker terminals.

Just some thoughts. Regards,
-- Al

falconquest,
an addition to my orig post keeping in mind Almarg's point #1 - if you can get a hold of a CD mat that experiment might also be useful. CD mats are often used to dampen vibration, squelch laser reflections & generally aid in producing clearer, more defined digital playback without overburdening the motor spinning the CD. I think this would be an additional good experiment, if feasible. Thanks.
P.S. to my previous post: My suggestion about cutting the speaker cable capacitance in half (as seen by the amp) assumes that one of the two biwire runs can be disconnected at BOTH ends, while leaving the other run in place and jumpering the high and low frequency speaker terminals. Disconnecting one of the runs at just one end, such as at the speaker terminals, will not result in a significant change to the cable capacitance that is seen by the amp.

Regards,
-- Al
 
It's not the player guys.  Such oscillations are downstream in the preamp or amp.
Interesting. One thing to do is to try it with the speakers disconnected.  Play through the piece, in a manner you are sure creates the problem, then connect the speakers.  Is the oscillation there? If so it's entirely electronic.  If not, it's electro-acoustical at least. :)

Best,


Erik