On Sunday, December 24, 2017 at 5:07:38 PM UTC-5, Phil Hobbs wrote:   
   > On 12/24/2017 04:46 PM, Steve Morris wrote:   
   > > On 25/12/17 07:21, tabbypurr@gmail.com wrote:   
   > >> On Sunday, 24 December 2017 19:47:00 UTC, Steve Morris  wrote:   
   > >>> I was wondering what would happen if I wired the output of a 100W audio   
   > >>> amplifier directly across a sizable (4700uF) electrolytic capacitor.   
   > >>>   
   > >>> It could be assumed the amp is push-pull and the cap is polarized.   
   > >>>   
   > >>> How would it react in terms of a test load?   
   > >>>   
   > >>> Steve Morris   
   > >>   
   > >> try sci.electronics.basics   
   > >>   
   > >    
   > > Do you post there too?   
   > >    
   > > Steve Morris   
   > >    
   > >    
   >    
   > Lots of us do.  No stigma attached, it's just not a design question.    
   > (Cross-posted to s.e.basics)   
   >    
   > The answer depends entirely on  whether the amp itself is stable with a    
   > pathological load like that, and (assuming that it is) what its input is    
   > and what the characteristics of the cap are.   
   >    
   > If the amp output is just sitting at zero volts, it isn't going to do    
   > anything dramatic to the cap.  If it oscillates, or if you put in a    
   > large AC signal, and the cap is a smallish polarized electrolytic (as    
   > opposed to a nonpolarized one), the cap probably isn't long for this    
   > world, unless the amp dies or current-limits first.   
   >    
   > The reactance of such a capacitor at (say) 10 kHz is   
   >    
   > Xc = 1/( 2 pi * 10kHz * 4.7e-6 F) = 3.3 milliohms,   
   >    
   > i.e. very nearly a short circuit.  The equivalent series resistance    
   > (ESR) is probably more than that, so the cap looks like a very low    
   > resistance.   
   >    
   > The net is that depending on the characteristics of the amp and what you    
   > put into it, your cap could be destroyed or could be completely unharmed.   
   >    
   > Actual audio people will probably have a better handle on how your    
   > average 100W amp will respond to such abuse.   
   >    
   > Cheers   
   >    
   > Phil Hobbs   
   >    
   > --    
   > Dr Philip C D Hobbs   
   > Principal Consultant   
   > ElectroOptical Innovations LLC / Hobbs ElectroOptics   
   > Optics, Electro-optics, Photonics, Analog Electronics   
   > Briarcliff Manor NY 10510   
   >    
   > http://electrooptical.net   
   > http://hobbs-eo.com   
      
   At least, use a light bulb.   
      
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