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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2\$\begingroup\$ Have you not come across a 5-pin headphone jack? \$\endgroup\$– Ignacio Vazquez-AbramsCommented May 27, 2017 at 15:33
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\$\begingroup\$ How does a 5 pin headphone jack disable speakers? \$\endgroup\$– MH0517Commented May 27, 2017 at 16:01
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1\$\begingroup\$ electronics.stackexchange.com/questions/95575/… Lots of audio amplifier IC have a mute pin, headphone detect mutes the speaker PA \$\endgroup\$– sstobbeCommented May 27, 2017 at 16:20
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\$\begingroup\$ There are 2 NC SPST switches inside them. \$\endgroup\$– Ignacio Vazquez-AbramsCommented May 27, 2017 at 16:22
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\$\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\$– MH0517Commented May 28, 2017 at 21:14
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1 Answer
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On the mechanical option for disconnecting speakers...
This is as old as the hills...probably 1960's. (An interweb search for '3.5mm socket changeover buy' leads you to some.)
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.
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.
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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\$ Commented May 27, 2017 at 16:46
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\$\begingroup\$ @TonyM Sorry to bump this old question, but do you have a searchable name for said "old as the hills...probably 1960's" connector? \$\endgroup\$– winnyCommented Feb 20, 2020 at 9:58
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\$\begingroup\$ @TonyM I just samt a search term for the passive-break-or-make-contacts-upon-insertion, not specific product recommendation. Thanks for the link! \$\endgroup\$– winnyCommented Feb 20, 2020 at 12:17
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\$\begingroup\$ @winny, you're welcome, thanks for upvoting this answer. \$\endgroup\$– TonyMCommented Feb 20, 2020 at 16:55