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    contaparte's Avatar
    contaparte Posts: 2, Reputation: 1
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    #1

    Apr 2, 2016, 08:47 AM
    Potentiometer to on/off switch
    Is it possible to replace the potentio-meter from a speaker with a on/off switch that would activate or deactivate the speaker?
    smoothy's Avatar
    smoothy Posts: 25,492, Reputation: 2853
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    #2

    Apr 2, 2016, 09:55 AM
    No.

    A potentiometer is a three legged resistor with the center leg adjustable. Its required to be there electronically for the proper biasing and function of the amplifier circuit.
    contaparte's Avatar
    contaparte Posts: 2, Reputation: 1
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    #3

    Apr 2, 2016, 10:18 AM
    All right thanks!
    cdad's Avatar
    cdad Posts: 12,700, Reputation: 1438
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    #4

    Apr 2, 2016, 11:49 AM
    You can replace it with a switch but if you add a resistor to get the proper value it will always be at one volume and non adjustable except with an outside source.
    Appzalien's Avatar
    Appzalien Posts: 540, Reputation: 57
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    #5

    Apr 3, 2016, 01:39 PM
    Some potentiometers have two functions. The first is a switching mechanism to turn the power off and it would be at the lowest volume setting if you go any further it clicks and the power is shut off. The second function is as you turn the volume up the resistance gets lower and lower as the dials connector slides along a winding of wire. Near the off position the resistance is greatest and very little juice gets through to the speakers. In the other direction resistance is lower and a lot more juice gets through and the volume gets louder. If you replace the potentiometer with a switch all juice gets through and the speakers will be at max volume. If the volume works but you cannot turn the speakers off any more you can add a switch to manually turn them off and let the dial do its thing. If it doesn't function at all check for loose or broken wires at both ends at the dial and the board. They're not that hard to replace if you can find the right size and variable resistance. If you go to radio shack you might find what you need there. If you want to remove the dial make sure you draw a good diagram of what color wires go where before you remove it or cut the wires real close to the potentiometer so you leave a little color showing for later reference. They can be as round as a quarter and smaller than a dime in circumference and fairly deep as well but as long as it fits the hole and doesn't touch anything inside you can try almost anything. Sometimes you can take one out of an old radio or go trash searching around the neighborhood to see what you can find. The switching type will typically have two sets of connectors, one for volume and one for off and on.
    smoothy's Avatar
    smoothy Posts: 25,492, Reputation: 2853
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    #6

    Apr 3, 2016, 01:57 PM
    Quote Originally Posted by Appzalien View Post
    Some potentiometers have two functions. The first is a switching mechanism to turn the power off and it would be at the lowest volume setting if you go any further it clicks and the power is shut off. The second function is as you turn the volume up the resistance gets lower and lower as the dials connector slides along a winding of wire. Near the off position the resistance is greatest and very little juice gets through to the speakers. In the other direction resistance is lower and a lot more juice gets through and the volume gets louder. If you replace the potentiometer with a switch all juice gets through and the speakers will be at max volume. If the volume works but you cannot turn the speakers off any more you can add a switch to manually turn them off and let the dial do its thing. If it doesn't function at all check for loose or broken wires at both ends at the dial and the board. They're not that hard to replace if you can find the right size and variable resistance. If you go to radio shack you might find what you need there. If you want to remove the dial make sure you draw a good diagram of what color wires go where before you remove it or cut the wires real close to the potentiometer so you leave a little color showing for later reference. They can be as round as a quarter and smaller than a dime in circumference and fairly deep as well but as long as it fits the hole and doesn't touch anything inside you can try almost anything. Sometimes you can take one out of an old radio or go trash searching around the neighborhood to see what you can find. The switching type will typically have two sets of connectors, one for volume and one for off and on.
    I have to chime in here... because there is a huge misconception out there that a volume control is like a water valve holding back the water that wants to get out.

    That could not be further from the truth. First they can not handle much current before they burn up. A Potientiometer is not a rheostat... they may look remotely alike and operate in much the same way..

    But a volume control works to tell the amplifier to work harder to put more out. Or work less to put less out...

    For the non-electronic engineers... compare it to a gas pedal in a car... its hooked to the carb or throttle body and basically tells the engine to go faster or slower.

    Your engine isn't running full throttle all the time while using your brakes to determine how fast you can go.

    It control's voltage levels to the pre-amplifier... any current changes are coincidental. The pre-amplifier makes a low level audio signal bigger... the final amplifier is what puts the punch behind it. But its not controlled by the volume control at all.

    Also putting a switch on the output of an amplifier is likely to kill it over time... if going from a nominal 8 ohms load to infinite resistance doesn't kill it... the voltage spikes generated from abruptly switching it between the two will eventually.

    Turn the power on or off if you want to do it... but trying to do it in this manner is going to turn it into junk over time.
    cdad's Avatar
    cdad Posts: 12,700, Reputation: 1438
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    #7

    Apr 4, 2016, 01:31 PM
    This might be a good place to drop this here.

    Making an Audio Power Amplifier (Drive a Sub Woofer) | ElectroBoom

    This guy is funny.
    Appzalien's Avatar
    Appzalien Posts: 540, Reputation: 57
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    #8

    Apr 6, 2016, 12:46 PM
    A rheostat is typically used in a higher power type application like 110 volt AC and a pontentiometer in a lower voltage DC circuit. It's basically an adjustable resistor which you can see by connecting the middle of the three connectors to either one of the outer connectors to a volt ohm meter in the ohms position and adjusting the knob. You will see that the resistance changes as the knob is turned. Sure it may tell the amp to boost power but it does it with resistance change. I mentioned the switch as a second fix if his dial also turns off the speaker set. A potentiometer like that has the three connectors for resistance change and a separate section with two connections for the switch. If that's what he has then removing the two switching wires and adding a new switch would allow him to continue to use the volume control but be able to turn it off completely without unplugging it from the power. You mean a gas peddle is not a valve holding back gas that wants to get out to the carburetor?
    smoothy's Avatar
    smoothy Posts: 25,492, Reputation: 2853
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    #9

    Apr 6, 2016, 01:23 PM
    Quote Originally Posted by Appzalien View Post
    A rheostat is typically used in a higher power type application like 110 volt AC and a pontentiometer in a lower voltage DC circuit. It's basically an adjustable resistor which you can see by connecting the middle of the three connectors to either one of the outer connectors to a volt ohm meter in the ohms position and adjusting the knob. You will see that the resistance changes as the knob is turned. Sure it may tell the amp to boost power but it does it with resistance change. I mentioned the switch as a second fix if his dial also turns off the speaker set. A potentiometer like that has the three connectors for resistance change and a separate section with two connections for the switch. If that's what he has then removing the two switching wires and adding a new switch would allow him to continue to use the volume control but be able to turn it off completely without unplugging it from the power. You mean a gas peddle is not a valve holding back gas that wants to get out to the carburetor?

    Ah.. but the gas wanting to get out of the Cab isn't connected to the wheels...

    You are correct about the power switch section... if his does have one there...

    However amps that have their power switch at the volume control VS a separate switch don't have a "soft start" circuit basically because power comes on at a min volume level... Amps that have a separate power switch if you have ever noticed don't slam on hard... where you actually hear the speakers pop. That will kill a speaker over time. Speaker cones have mass and as such... can't move from a rest position to fully extended in zero milliseconds.

    Even percussion instruments like a drum does not have what equates to instantaneous rise time from zero to any certain output level like a square wave does... every audio signal through an amp is a sinusoidal wave, group of waves and harmonics of those waves.

    A square wave in theory is a sinusoidal wave with an infinite amount of harmonics.. but in practice an audio amp has a minimum designed response frequency and a maximum before rolling off to insignificant levels. SO in practice... you will never get a pure square wave through an amp and you can damage equipment trying.

    Also if you've ever looked at digital signals through an Oscilloscope... its really rare you will actually see a theoretical pure square wave either unless it's a really low speed device.

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