What happens inside an amplifier?

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

  1. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    Love the foot on the accelerator analogy. Another one I've heard is a hand controlling a water spigot. A small turn one way or the other increases or decreases a stream of water from a trickle to a fire hose. Imagine the hand turning rapidly back and forth in time to the music.
     
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  2. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    "It goes in here, it goes around and around, and it comes out here."
     
  3. damacman

    damacman Blown and Injected Subscriber

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    In the spirit of the same explanation your friend gave ... An amplifier takes small signals and turns them into larger ones by increasing their amplitude.
     
  4. z-adamson

    z-adamson AK Subscriber Subscriber

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    Turn your attention to the dictionary...

    TO AMPLIFY...............

    • increase the amplitude of (an electrical signal or other oscillation).
    • cause to become more marked or intense.
    An amplifier does this ^^^^

    How? Well, that gets complicated. First of all, I am underqualified to go into detail and second of all, even is I was qualified, it would be too much to simplify and put into an internet forum post.
     
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  5. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    I think some of us are trying too hard to compress technical info into a small package. Forget the technical info. OP is looking for 'painting with light' analogies.
     
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  6. birchoak

    birchoak Hi-Fi Nut Subscriber

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    (In Austin Powers voice) Yeah, Baby! That's what I needed!
     

     

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  7. birchoak

    birchoak Hi-Fi Nut Subscriber

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    Yes, thank you. Analogies. And believe me, I know that it takes a tremendous amount of experience & knowledge to be able to provide analogies for something this complicated. That's why I turned to you folks. I could give you carpentry analogies because I'm a carpenter.
     
  8. birchoak

    birchoak Hi-Fi Nut Subscriber

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  9. gdmoore28

    gdmoore28 Super Member

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    I kid you not - read this book. You will be educated in an understandable way, and you will laugh your yaya off all the way thru.

    Oh - and he'll also explain how an amplifier works.

    [​IMG]

    GeeDeeEmm
     
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  10. Powertech

    Powertech Active Member

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    An interesting angle on transistors I was one told about.
    The word 'transistor' comes from transfer resistor. As a small voltage varies at the base connection, the resistance between the collector and emitter will vary. If the power supply is connected to the collector, a small variation in voltage at the base, a large variation in voltage appears at the emitter at a constant ratio. Hence, the circuit amplifies.

    I thought that was quite a tidy explanation.
     
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  11. cpt_paranoia

    cpt_paranoia Active Member

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    Very good analogy, especially in terms of the concept of power amplification (by controlling a power source, be it electrical or ICE).

    Provided you have a right foot that can move very quickly...

    It also provides an analogue for feedback; we use engine tone or speedo to provide feedback to our right foot, thus controlling what we actually want to achieve.

    Vacuum tubes are named as their exact fluid control analogues; valves. Transistor behaviour can be explained by the same analogue; a flow-control valve. Diodes can be explained by non-return valves.
     

     

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  12. Ray Gianelli

    Ray Gianelli AK Subscriber Subscriber

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    @birchoak

    In the end an amplifier essentially modulates the power supply by the input signal:

    PS.png
    When a signal is input into a complementary amplifier, the positive going part of the signal rises to the positive rail and will push the speaker cone outward. As the signal goes through the zero volt point and goes toward the negative rail, the speaker cone will be pulled in.

    If the signal is too high it will hit the limits of the power supply rails and can go no higher. When viewed on an oscilloscope, the tops and bottoms of the sine wave would be cut off, hence the term "clipping".

    That's about as simple as I can get it.
     
  13. birchoak

    birchoak Hi-Fi Nut Subscriber

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    Oh man, thank you! I do best with a dash of humor, so this might be a good fit!
    Book ordered from Amazon!
     
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  14. SaSi

    SaSi Seriously Illogical Subscriber

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    How about this analogy:
    The amplifier is a power supply that takes power from the AC outlet and modulates it using the input signal, to create a more powerful version of the input signal and drive the speakers.

    All that the various circuits of a power amplifier do is prepare the input signal to drive the output transistors that take the power supply power and create the output.
     
  15. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    When I first read the OP’s post, the car analogy was the first thing to pop into my head too. Along the lines of using gasoline and an engine to make your foot (and hopefully you still attached to it) travel faster than it can by itself.

    Speaking of this topic, does anyone remember the electronics book from the 50s/60s that was linked here a while back in PDF form? I think it was in like 4 parts/sections or something. I remember downloading all of it to my phone to read and refer to, but during my latest update to iOS i accidentally ‘reset as new’ and ended up losing those along with a number of different service manuals for equipment. I’ve got the service manuals since most were either from AKDatabase or HiFi/Vinylengine, but I can’t seem to track down the thread where a member posted them.

    If you remember the thread or can share the links I’d appreciate it, and I think it might help the OP and others understand some stuff too. Thanks!
     
  16. lini

    lini just me...

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    Actually I don't quite like the analogy of "painting with light" for photography - in my view "painting with light" would rather fit to creating an image on a CRT monitor.


    Ray: I think "controlling" (a power supply output by an input signal) would be more precise than "modulating" - but that might be more of a functional description than an analogy, anyway. The same might go for "creating an enlarged facsimile of an electric input signal". Currently I'm thinking of one of the lever contraptions, with which one can draw something, while a second pen would simulataneously draw a larger copy - used as a seismograph (e.g. with a paper roll transport mechanism similar to that of for example a barograph). But while that would fulfil the aspect of something being turned into something larger, this would rather be more similar to a transformer, as it just transforms the initial input energy - so that would still not cover the aspect of the initial energy controlling a larger (or at least more robust) energy to form its enlarged (or at least more robust) facsimile. Hmmm, difficult...


    Greetings from Munich!

    Manfred / lini
     
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  17. Natitude

    Natitude Super Member

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    :jump:
     
  18. BassKulcha

    BassKulcha Unrepentant Anachrophile Subscriber

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    Rey, you may be thinking of Norman Crowhurst’s Basic Audio:
    https://archive.org/details/Basic_Audio_Norman_Crowhurst_1959_Volume_1


    I actually purchased a vintage hard-bound copy online from ABE books. I find it much more enjoyable to read than the PDF. Highly recommended...
     
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  19. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    That’s it! IDK why I was thinking it was specifically electronics, but that’s definitely the book I was referring to.

    Thank you!
     
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  20. ev13wt

    ev13wt Super Member

    AC enters your unit. Voltage gets lowered to whatever the system is designed to use. Lets say 70V.
    Full-wave rectification converts both polarities of the input waveform to pulsating DC.
    Caps smooth out the pulses so you have a steady stream of DC.

    An AC signal also enters your unit. This is the music signal. It is very tiny and cannot move a speaker back and forth (AC, back and forth, speaker back and forth...)

    The amplifier has a little device that basically sees the tiny AC input and uses large DC current. Like power steering, small inputs simply get a helping big push. A form of this in aufio is you have two power steering helper units, one does the left turns and one the right turns.

    Problems with this stuff:
    As the music signal passes though "zero", it can distort. Like steering, the middle point is usally where you can move the steering wheel a bit but nothing happens. (sort of like that)
    The current needed by the transistor varies, and the power supply must be able to deliver high current very quickly and smoothly.
     

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