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I've researched this for a while now and can't find any answers for the life of me.. How can I add a headphone jack to an audio amp with speakers that disables the speakers when headphones are plugged in? There are only two possible explanations I can think of: there would have to be some sort of physical switch that cuts the speaker lines when headphones are plugged in, or something would have to be coded in a chip to disable the speakers. Can someone tell me how it's done?

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    \$\begingroup\$ Have you not come across a 5-pin headphone jack? \$\endgroup\$ – Ignacio Vazquez-Abrams May 27 '17 at 15:33
  • \$\begingroup\$ How does a 5 pin headphone jack disable speakers? \$\endgroup\$ – MH0517 May 27 '17 at 16:01
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    \$\begingroup\$ electronics.stackexchange.com/questions/95575/… Lots of audio amplifier IC have a mute pin, headphone detect mutes the speaker PA \$\endgroup\$ – sstobbe May 27 '17 at 16:20
  • \$\begingroup\$ There are 2 NC SPST switches inside them. \$\endgroup\$ – Ignacio Vazquez-Abrams May 27 '17 at 16:22
  • \$\begingroup\$ @sstobbe my amp does in fact have a mute pin. What pin on the headphone jack do I wire the mute pin to so the speakers will mute? \$\endgroup\$ – MH0517 May 28 '17 at 21:14
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On the mechanical option for disconnecting speakers...

This is as old as the hills...probably 1960's.

1 is GND 2 is AmpL and normally connected to 4 SpkrL 3 is AmpR and normally connected to 5 SpkrR

When you plug the headphones in, 2/3 are sprung away from 4/5 to disconnect the speakers and are now connected to the headphones. Unfortunately, all of the speaker power is now being thumped into the headphones. If the headphones have a different/higher impedance to normal speakers, as they certainly do these days, it sounds trebley.

enter image description here

On the electronic option...

Here's an example circuit, showing one way of doing it. When the headphones are plugged in, the resistors pull the detect voltage to high and constant. This signals to the amplifier circuit to deliver a signal suitable for headphones.

enter image description here

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  • \$\begingroup\$ Contact is "normal closed" when no plug is in, and when plugged it opens. Better tie the 100k resistor to Vcc rather than GND and remove the other resistor. \$\endgroup\$ – Todor Simeonov May 27 '17 at 16:46

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