From: legg@nospam.magma.ca   
      
   On Sun, 25 Sep 2022 19:40:36 -0700, Jeff Liebermann    
   wrote:   
      
   >On Sun, 25 Sep 2022 11:23:10 -0700 (PDT), Joe Jaramillo   
   > wrote:   
   >   
   >>I have the same problem on a C 430.   I’ll be playing either quiet or loud   
   and then a hear A rumbling noise that kind of trails off for a bit and then   
   comes back. Did you ever find out what the root cause was?   
   >   
   >There's an important clue in the text:   
   >"It goes away when you plug headphones"   
   >   
   >My guess(tm) is it's some form of microphonics.  That's where the   
   >speakers cause some electribuc component to vibrate, which then causes   
   >audible noises in the speakers.  If the gain and phase of the   
   >amplifier is correct, it will produce low frequency feedback, which is   
   >the rumbling noise you hear.  If the noise was a high pitched squeal,   
   >then it would be high frequency feedback.   
   >   
   >In your case, you have a "C 430".  That might be a Yamaha NX-C430   
   >speaker system.  The system does not have any built in amplifier(s),   
   >so there's nothing wrong with the speakers.  I suggest you remove your   
   >speakers from the amplifier or receiver case, and the microphonics   
   >will likely be reduced or stop.   
      
   You might check boards for degrading adhesive employed in tack-on or   
   harness security, in this case - after the volume control section.   
      
   RL   
   >   
   >Incidentally, you're only 19 years too late to catch the original   
   >posters.   
   >   
   >>On Wednesday, March 12, 2003 at 9:56:01 AM UTC-8, Michael and Janet Inman   
   wrote:   
   >>> I have a Yamaha CLP-411 Clavinova that is about five years old. It has   
   >>> developed an occasional rumbling sound that comes from both speakers.   
   >>> It only lasts a few seconds at a time, is unbelievable loud, very low in   
   >>> pitch, and sounds just like wind noise on a microphone. Seems to happen at   
   >>> random times although more common when someone is playing it. Volume   
   >>> control position has no effect on the noise volume but does sometimes seem   
   >>> to affect the timbre of the noise. It goes away when you plug headphones in   
   >>> (you don't hear it in the headphones).   
   >>> Without the benefit of a service manual/schematic, I have tried to trace   
   the   
   >>> analog audio signal with an oscilloscope to at least determine from which   
   >>> stage the noise is coming. I'm suspecting it's originating in the power amp   
   >>> section - the amps are IC "bricks", one for each channel but since it's in   
   >>> both speakers equally I'm thinking it's not them. Due to the sheer volume   
   >>> of the noise it actually loads the power supply to a point where signals at   
   >>> all stages are affected. I did change the filter cap in the dc supply. No   
   >>> improvement.   
   >>> I did read some newsgroup accounts of noise in the Clavinovas being due to   
   >>> dirty contacts in the volume control... I'm picking up some contact cleaner   
   >>> today and will try that but I'm not too optimistic about it.   
   >>> Any experience with this problem or guidance much appreciated.   
   >>> Mike   
      
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