From: joej1959@gmail.com   
      
   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?   
      
      
   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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