QUAD 405 power off noise

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Like pfiuuuuu....and than thump...and woofer cone movements....
Check Bernd Ludwig's text ....google it.
It is because op amp shuts down before rest of the amp....
You can modify a lot....add a lot ....or just leave as is. It is nothing wrong with your amp it is just old Quad.
Cheers, Taj
 
My experience of a Quad 405 Mk 1 clone was good, without any unpleasantness at power up or down. However, when I played about with replacing the LM318 op amp with something more modern, I got thumps at power up and, I think, even a squeal of oscillation at power down.
 
I'm afraid yes.
Did you check supply voltage at op amp? It should be +-15V. I don't know about 134 op amp but if it draws too much current...
Check datasheet or measure it. And be careful. Don't short something.
If noise bothers you it is possible to install some sort of dc protection using relay which act as power on delay as well. There is plenty of such ideas around. Just google it. Again ,,Bernd Ludwig,, text. It is a lot useful information there.
Cheers
 
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