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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?
128x128falconquest
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bombaywalla
1,958 posts
 
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.
almarg's avatar
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almarg
9,670 posts
 
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
 
stevecham
3,340 posts
 
It's not the player guys.  Such oscillations are downstream in the preamp or amp.
erik_squires
16,283 posts
 
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
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