Author Topic: DIY: Setting amplifier gains by ear  (Read 762 times)

August 04, 2013, 10:05 PM #0

Bmoney Offline

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In the absence of an o-scope and test tones, you can get your car audio amplifiers gains setup "really close" by ear.

1.  choose program material you're very familiar with - something cleanly recorded
2.  back all gains on all amps out to zero
3.  ensure crossover (if being used on the amps) are set correctly (another DIY to come)
4.  set all tone controls on radio to flat - turn off all boosts, gains, media expanders, etc. 
5.  play your chosen program material - set radio volume to approximately 75% of wide open (if volume goes to 100, set to 75, etc)
6.  if you're running deck power up front and you're setting up a sub amp, set the volume to the maximum undistorted volume (this will vary wildly from setup to setup). 
7.  for subwoofers - slowly back the gain in, listening very closely to the sub.  Don't worry about "volume" so much as "stress".  Listen intently for signs of distress.  As you back the gain in, you should get a clean increase in output.  The point where this increase stops is likely also the point where the sub begins to stress.  At this point, stop. 
7.1  for speakers, do the same.  But listen to those speakers...listen for stress.  Listen for distortion.  Any sign of trouble.  At this point, stop.
8.  turn the gain down just a touch
9.  play a few more dynamic tracks - making sure that you don't get any signs of distress on any of them

There you have it - the "tune by ear" method. 
Last Edit: December 11, 2014, 10:54 AM by Ænimal

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    DIY: Setting amplifier gains by ear
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    August 04, 2013, 11:03 PM #1

    jordisonjr Offline

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    After reading this, I've realized my understanding of gain was far from correct.
    Care to explain?
    Originally posted by Madbuzz41
    I'm not a fan of blowing for a long time anyways ; )


    [Mar 31 23:03:18] Basil:Dan go outside without your pants and let your beef curtains flap around in the wind like a windsock

    [Dec 11 14:00:38] alexatwork21:I

      August 04, 2013, 11:15 PM #2

      Bmoney Offline

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      what am I explaining again?

        August 04, 2013, 11:16 PM #3

        jordisonjr Offline

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        This thread shows how to set gain, but I'm sure majority of the people on here don't really know what gain is.
        Or maybe it's just me..
        Originally posted by Madbuzz41
        I'm not a fan of blowing for a long time anyways ; )


        [Mar 31 23:03:18] Basil:Dan go outside without your pants and let your beef curtains flap around in the wind like a windsock

        [Dec 11 14:00:38] alexatwork21:I

          August 04, 2013, 11:23 PM #4

          Bmoney Offline

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          Gotcha.  The simplest way to put it is this - in the aftermarket, radios come in all shapes and sizes...and all sorts of preamp output levels (the "strength" of the radios audio signal, measured in volts).  Weaker radios will have less than 1 volt of output.  Stronger preamps will have 4-5 volts or more.  Knowing this, amplifier manufacturers needed a way to match the amplifiers input stage with the radios output stage - and gain was born.  Higher voltage radio preamps require a lot less gain on the amplifier to reach maximum output - which usually yields quieter performance (less induced noise). 

          In essence - the gain is a setting that allows the radio and amplifier to reach maximum output at the same time.  If the gain on the amp is set too high, maximum output on the amp is reached far before "top volume" on the radio.  If the gain is set too low, when the radio is wide open, the amp will still have some horsepower left.

          The temptation is to set the gain "higher" to make things "louder".  The danger is that the amp will only make so much power - driving the inputs past this electrical limit yields a magical thing called clipping - where the amps power supply tries to reproduce the signal, but cannot (reaches electrical limit) and clips the tops and bottoms of the wave.  This clipping appears to a typical speaker as a form of destructive distortion.  This distortion builds as heat in the voicecoil in the speaker its driving - and leads to failure. 

          In almost every "blown speaker or sub" situation I've ever come across, the culprit was a maladjusted gain that drove the amp wildly into clipping - which killed the driver.  Power is NOT the enemy of a speaker - HEAT is  :)  Look close at most speakers power handling rating - some will advertise it as a "thermal" rating.  Its not that the speaker can handle "100w of power".  Its that it can dissipate "100w worth of heat".    :trollface:
          Last Edit: August 04, 2013, 11:28 PM by Bmoney

            August 04, 2013, 11:25 PM #5

            Bmoney Offline

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              DIY - setting amplifier gains by ear
              « Reply #5 on: August 04, 2013, 11:25 PM »