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previous: Armand Great thread. I learn something new... -- 5/14/2003 10:31 AM view thread

Re: Help! Negative Feeback Switch Popping!

5/15/2003 4:49 AM
Enzo
Re: Help! Negative Feeback Switch Popping!
Armand  
I think he was popping for the reasons I outlined in my earlier post - he is switching DC levels abruptly in the signal path. That is amplified as a pop.  
 
This is a completely different source of popping from your power and standby switches. In both your case and his the switch is not the problem, only the agent of the problem.  
 
When you power down your switch breaks the power circuit. Some inductive kick from the power transformer kicks that up to a spark across the opening switch contaacts. Depending on where in the cycle the mains AC was when you opened the switch, the arc transient may be large - if you switch at peak - or minimal - if you switch at zero crossing.  
 
Your standby pop is related. WHen you flip to standby, you are breaking, usually, a high voltage DC line. It arcs the switch and your amp amplifies the arc as the caps discharrge.  
 
These pops are not usually anything threatening the amp in any way.  
 
The switch itself is irrelevant. No matter how "fast" the switch closes or opens, electricity move much much faster. You want to cut down on arcing. A cap across the switch might help. A varistor might help. A cap and/or varistor across the tranny primary might help.  
 
SInce the power supply in the amp does not discharge instantly, it amplifies the noise of that spark as it fades out. The arc is a fine source of broadband energy - it radiates a signal easy to pick up.

 
Replies:
Armand Thanks Enzo. But I'd like to know w... -- 5/15/2003 3:20 PM