cambridge audio amp , mission m71 soeakers , problem?

[robgilmo]

hi guys. i have just taken my old amp and speakers out of the garage where they have been in storage for 4 or 5 years. they were working ok when i packed them up.

they still work ok except when i turn off the amp it powers down after a few seconds however i get a thump from the left hand speaker just as the light fades out.
any ideas?

 

[RobHolt]

Should be nothing to worry about.
The power supply capacitors inside the amp act like a battery for a few seconds after you switch off, so the amp suns for a few seconds then dies.

If the amp still sounds ok and is electrically quiet in use, nothing need be done.

 

[robgilmo]

Thanks for the quick reply Rob , i understand the thumping can be normal but this is quite noticeable both on start up and when i switch it off except when i switch it off it also makes a sound like a stylus being dragged over a record , just for a split second.

 

[Dev]

I have the same issue with my amp. It's annoying but hopefully doesn't hurt the speakers. On my 2nd system, the amp has 2 sets of outputs. I just turn the speaker output to the spare before switching off to avoid the thump.

 

[robgilmo]

cheers Dev , its not so much the thump i am worried about , more the screeching sound. i keep thinking my turn table has just destroyed one of my records.

 

[RobHolt]

cheers Dev , its not so much the thump i am worried about , more the screeching sound. i keep thinking my turn table has just destroyed one of my records.

It results from different parts of the amp shutting down at different times.
Usually, as the supply voltage falls the power amp continues to function while op amp (chip) based parts of the circuit shut down. They don't shut down cleanly which is why you get squelching noises.

Still wouldn't worry.