What happens inside an amplifier?

Discussion in 'General Audio Discussion' started by birchoak, Jun 11, 2018.

  1. birchoak

    birchoak Hi-Fi Nut Subscriber

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    In my never-ending journey to understand vintage electronics, I find myself looking for footholds, concepts I do actually understand, to help me decipher what I don't understand. When I was a photographer, someone told me, "All a camera does is hold the film flat so that the lens can focus an image on it. You are painting with light." I never forgot that, and understanding the overall concept really helped to guide me through f-stops, shutter speeds, film speed, etc.

    Can anyone explain what happens to electricity as it enters a vintage receiver/amplifier and makes its way through the various circuits? Feel free to explain as if to a small child: Mr. Electron is in a big hurry! He is also very lazy and will always take the easiest, quickest ground, even if the path is through your finger! What in the hell is going on in there? Why is there a bridge rectifier? Why do we need so many damned caps?

    Even if it pains your great mind, please oversimplify so that a mere mortal may comprehend what's going on behind the green curtain (Wizard of Oz reference; nothing naughty). I know the difference between AC and DC and not a heck of a lot more than that.
     
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  2. mhardy6647

    mhardy6647 AK Subscriber Subscriber

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  3. mhardy6647

    mhardy6647 AK Subscriber Subscriber

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    Oh, the other thing you should know, if you don't, is Ohm's Law.

    E = I * R

    E = voltage (volts)
    I = current (amps)
    R = resistance (ohms)

    Power (P, in watts) = I^2 * R = E * I

    Those interrelationships enable pretty much everything in electricity and in electronic circuits.

    [​IMG]
     
  4. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    Maybe this is an oversimplification.
    Power from your wall is converted from AC current to DC current.
    It creates a reservoir or energy to be used.
    The low level signal (for sake of leaving out the eq curves on lps lets take a line source.
    The low level signal acts as the control of a very sensitive valve. As the frequency and the volume (amplitude) of the signal changes, so does the flow of the stored up energy (the reservoir ) is released in proportion to the original signal to your speakers. A little bit of signal releases a lot of signal. Clear as mud right?
     
    Last edited: Jun 14, 2018 at 12:37 PM
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  5. petehall347

    petehall347 the brandy coffee man Subscriber

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    a small amount of alternating electric current pulses enter the amplifier then it gets added to along the way ending up with a much larger alternating electric current to make the speakers move in or out thus resulting in the air being moved around playing the music . there are a few designs of audio amplifiers but all end up at the speakers making the sound .
     
  6. darkblue94

    darkblue94 It wasn't me. Subscriber

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    At least one time in my case it was a loud bang and flash of light followed by the dreaded magic smoke. Not recommended. :yikes:
     
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  7. Ken Boyd

    Ken Boyd Lunatic Member

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    Depends on if your vintage is SS or Tube but both simply take a small signal voltage that comes in from your source, takes power from your panel thru a receptacle and uses that power to copy the small voltage coming in and boast it to levels that push a linear motor as close to possible of that small signal to push air, just like the air that pushed the microphone diaphragm that recorded the music.
     
  8. autoanalog

    autoanalog Justin Credible Subscriber

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    3324DE3A-CFB2-4C9F-8CDB-E2EEAF094CB4.jpeg

    Some say that electrons inside an audio amplifier undergo something akin to a religious experience.
     
    Last edited: Jun 11, 2018
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  9. birchoak

    birchoak Hi-Fi Nut Subscriber

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    I love that cartoon! I don't think most people would get it, so it makes me feel smart LOL.
     
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  10. birchoak

    birchoak Hi-Fi Nut Subscriber

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    This really helps. Nice and simple, tells me the big picture. Linear motor = speaker, right? Beautiful summary, and when you talk about pushing air I really get it!
     
  11. birchoak

    birchoak Hi-Fi Nut Subscriber

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    The amp is replicating the signal but also enlarging it, like enlarging a print from a photo negative?
     

     

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  12. birchoak

    birchoak Hi-Fi Nut Subscriber

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    I will give them a look, but hearing someone try to explain it in a few sentences would help me more--I need an overarching, view-from-outer-space take on what that amplifier is doing to the AC entering it.
     
  13. birchoak

    birchoak Hi-Fi Nut Subscriber

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    Please wait a moment, OP's brain rebooting after system crash.
     
  14. birchoak

    birchoak Hi-Fi Nut Subscriber

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    Oh, I know the magic smoke well, my friend. Shut off your Harman Kardon 630 Twin before inserting the PRE/MAIN jumpers.
     
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  15. the skipper

    the skipper Amateur Curmudgeon Subscriber

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    So, what you're asking is basically "Teach me all about electronics in one simple post." It ain't gonna happen. It's a bit more complex than that.

    NJ Phoenix gave you a pretty good nutshell summation as to WHAT happens in post 4. A small voltage controls a large voltage. Now, as to exactly HOW it happens, well, that will take a bit of knowledge in basic electronics, and that will take a bit of effort on your part.. You might want to read and digest the books suggested by Mr Hardy in post 2.
     
    Last edited: Jun 11, 2018
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  16. BinaryMike

    BinaryMike Pelagic EE Subscriber

    Maybe this will help: An amplifier performs much the same service for an input signal as the engine in a car performs for the small movements of your right foot --- they both increase signal power by several orders of magnitude.
     

     

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  17. musichal

    musichal poet emeritus Subscriber

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    It's all magic. Electricity only works because so many of us believe in it.
     
  18. mhardy6647

    mhardy6647 AK Subscriber Subscriber

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  19. lini

    lini just me...

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    birchoak: Basically you could regard any amplifier as an adjustable/controlled power supply (or rather voltage supply in case of (small) signal transmission, in which power transmission is pretty negligible and only of secondary interest...), the output of which is primarily adjusted/controlled by an external signal, that's fed to a suitable input the "power supply"/amplifier provides for that purpose, and which is optimised for the requirements of both at least one certain control signal source type and at least one certain type of load (or receiving device in case of signal transmission).

    Greetings from Munich!

    Manfred / lini
     
  20. lini

    lini just me...

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    Oh, and before anyone would ask: Passive pre-amps indeed wouldn't fit to that definition, due to not really being amplifiers at all. However, that term nevertheless isn't that wrong, if one understands it in a somewhat different sense - 'cause not only would passive pre-amps still provide two important functions that regular, active pre-amps also provide, namely volume control and source selection, but one could also understand "pre-amp" in the sense of "the device before (= pre) the (actual power-)amp" (providing some control funtions for the signal that goes to the power-amp, without being an amp itself...).

    Greetings from Munich!

    Manfred / lini
     

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