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An argument for fuses and maybe power cables in power amplifier

There are a lot of discussion about fuse but I don't remember a thread that include

an actual circuit.

The circuit below is called a rectifier which converts AC voltage from the wall to DC voltage that feeds to audio power amplifier.  All if not most power audio amplifier uses this topology.  Some have bigger transformer, some have more capacitors, some have higher voltage output but most are more or less the same.  Audio amplifer uses a lot of current so they don't use a regular which may even degrade the supply, therefore most will just use what you see below as a rectifier circuit.

You can see from the circuit the current comes from the wall, the AC source far left, to the fuse, F1 5A upper left, go through the transformer then to the diode rectifier, D1 D2 D3 D4, then finally to the 25+/- supply source which then will feed to the power audio amplifier.  

So you can see the fuse is clearly in the signal path.

As for the power cable, it is harder to understand.  Most power cable are already  beefy enough to handle the current so having an even beefier cable will help is something that needs further reasoning.

andy2
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rodman99999
6,171 posts
 

The why after market power cords make a difference?  Lots of theory... Actual testing using testing equipment? Just my ears. I don’t watch oscilloscope screens or listen to test tones.  Just music, using my ears. 

                                       And: that's ALL that matters!

                                                     YMMV

                                                           +1

      Some people just don't seem to understand; there are a plethora of variables.

                                                  Happy listening!

kijanki's avatar
kijanki
4,432 posts
 

Linear power supply is really a primitive switcher operating at 120Hz.  Current is drawn from the mains in narrow spikes of high amplitude, that become wider when load increases.  In addition rectifiers become reverse polarized at the peak of the voltage conducting for a moment in the opposite direction creating narrow spike that couples to any, even smallest inductance in the circuit.  

The fact that current is drawn in narrow spikes has serious consequences.  Transformer has to be larger than one with resistive load, because higher rms to average current ratio is causing bigger losses in windings, while high frequency content increases core losses (eddy currents, hysteresis).  These narrow current spikes of high amplitude travel thru fuse and power cable making things very complex.  

As for the power delivery, it should be obvious from the definition of electric current (flow of electric charge), that the exactly same amount of electric charge leaving one leg of power supply comes back in another.  Power has to be delivered different way.  Current in the wire creates magnetic field around conductor while presence of load makes voltage drop - an electric filed.  These fields cross each other like X-Y axis while Z axis perpendicular to them shows direction of the power delivery (Poynting vector).  Power is absorbed by the load from electromagnetic wave.

To improve linear power supply circuit I would look for “soft” rectifier (like Hexfred) , that, after conducting for a moment reverse polarized, don’t snap back too fast (wider spikes are better).  I would also look for low inductance electrolytic capacitors, like “slit foil” type.  0.1uF capacitor in parallel helps, but with large inductance of main capacitors can create parallel resonance circuit and possible ringing.

 

asvjerry's avatar
asvjerry
4,738 posts
 

@rodman99999 .....*slow clapping* { it's late....the cats are asleep}

Thenk you, Dr. Whiplash..... ;)
 

Some people just don't seem to understand; there are a plethora of variables.

....and, given that bit of clarity; 'X' = Infinity, macro v. mega, everywhere in everything...even in the 'nothing' of space....

   They know
 What is What
         BUT
They Don't Know
   What is What
     It just suks

Back to the Theories! *G*👍

Actually, rodman9x5, that was actually entertaining.....
 

rodman99999
6,171 posts
 

@asvjerry -

   They know
 What is What
         BUT
They Don't Know
   What is What
     It just suks

            Funny!     AND: a snowflake had me deleted, just recently, for saying, "it's like teaching a box of rocks, to sort your socks!", in their exhausting, er.. I mean: exhaustive thread.

                                   Put another way:  

            The problem with naysayers isn't that they're ignorant.

             Rather: it's they're knowing so much that's incorrect*.

                            *The very heart of Dunning-Kruger

                                          Happy listening!

 

                              ps: The nines are exponential.   

 

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