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I have a set of speakers with an additional stereo headphone output on the front. As it is now, when the headphones are plugged in, the speaker mutes, giving output to the headphones alone.

I want to stop this headphone jack from muting the speakers when something is plugged in.

Obviously this is a typical design of a speaker/amp with a headphone jack. In my case, I just happen to want to change that. I opened it up and have see everything there, but I don't know exactly what I'm looking at. I can solder if I'm sure that I'm sure it's a solution.

Check out the pictures & diagram / schematic. Is this possible? Somehow to disengage the MUTE function?

Front of Speaker

Closeup of Headphone Jack Board

Back of Speaker

Speaker Diagram

View Inside Speaker 1 (headphone jack board on bottom left)

View Inside Speaker 2

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3 Answers 3

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What you seek may not be possible, or if it is, you need schematics instead of the signal flow diagram.

What the headphone connector does is that when there is no phones inserted, the connector shorts the mute pin together with left and right audio signals of the phones. Which means it also shorts the left and right signals together.

When heeadphones are plugged in, the connector disconnects the mute wire from left and right signals.

As the left and right signals for the phones must be small voltage signal around 0V GND, it might be enough that you permanently connect the mute wire to ground, but it might not be a great idea to leave it connected to the left and right audio signals then.

Try measuring with a multimeter what voltages are on left, right, and mute wires when connector is unplugged and inserted. Or, find the real schematics.

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The pad labeled "HP DET" is what is telling the power amp to turn on or off. Desolder the wire, find another pad that it connects to with the headphones removed (RCH or LCH, by the look of it), and re-attach the wire there.

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  • \$\begingroup\$ I quickly tried connecting a wire to make contact to the LCH & HPDET on the back of those pads as pictured (since they are right beside each other it was easy) and the speakers turned back on, but the headphones muted... Any ideas if that helps elaborate how this works? \$\endgroup\$
    – Noah Taher
    Commented Mar 14 at 19:30
  • \$\begingroup\$ @NoahTaher As in my answer, it might need to be connected to both L and R to determine the mute status. But now it seems your problem isn't deactivating the mute but wire up a subwoofer, which you can do otherwise by adding outputs taken from e.g. headphone amp inputs. \$\endgroup\$
    – Justme
    Commented Mar 15 at 10:46
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It might be easier to get a "line (RCA) to headphone (3.5mm)" amplifier and plug it into the "LINE 2" jacks. Then, you use the volume control on the source to adjust both the speakers and the headphones. Which you might have to do it my way anyway because what you are trying to do provides no way to independently control the relative volume between the headphones and the speakers.

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  • \$\begingroup\$ So, the LINE 2 is actually an input, not an output :( sadly. I actually want to add a subwoofer post-volume on the monitors using the headphone jack - that's my goal. \$\endgroup\$
    – Noah Taher
    Commented Mar 14 at 23:52
  • \$\begingroup\$ @NoahTaher Well that explains your weird use case - I was wandering why someone would want to wear headphones while at the same time blasting the same audio content through the speakers! First, the "LINE 2" is intended to be an input, but according to the schematic, it's depicted as an output. You should check that. Second, if I'm wrong, you're going to have to get a "Y" splitter so the signal can get to the speakers and the sub - volume, again, will be controlled by the source device. Easiest way, and gives you independent control of both satellites and sub(s). \$\endgroup\$
    – MOSFET
    Commented Mar 15 at 4:06
  • \$\begingroup\$ @NoahTaher You should have mentioned you want to attach a sub that is post-volume control. Then the problem is not how to modify the headphone output to not mute, as you likely don't want to connect the sub to a headphone amp circuit, it may have some bass filtered out as you would not want to pass too low frequencies to headphones. \$\endgroup\$
    – Justme
    Commented Mar 15 at 7:27
  • \$\begingroup\$ @MOSFET That is a signal flow diagram as seen for audio gear - all inputs are on left and outputs are on right. \$\endgroup\$
    – Justme
    Commented Mar 15 at 7:28
  • \$\begingroup\$ @Justme I see a differential line driver from "LINE 1" feeding "LINE 2". But if what you are saying is correct, if used together, LINE 1 inputs and LINE 2 inputs could be used as a mixer? \$\endgroup\$
    – MOSFET
    Commented Mar 15 at 7:36

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