speaker isolation

Hello,

I made a portable enclosure for a car radio that has a negative ground but the left and right speaker outputs have isolated grounds from each other and the chassis.

I needed to common out the (-) from the left and right speakers in order to attach them to the common connection on the headphone jack. I successfully connected each of the (-) outputs from the left and right speakers using non-polarized 47 uf electrolytic capacitors and joined the ends of the caps to the headphone jack.

All is well when the jack is floating and un mounted, but when I mount the jack to the chassis, even though the audio output is great, I get annoying loud "clicks" and "pops" when I wiggle the headphone plug/jack, most likely because of the caps discharging/charging.

Other than figuring a way to physically isolate the headphone jack from the chassis, is there a way to drain the charge using resistors, and if so, what values do you suggest?

Thank you for your help,

Ivan

Oh boy. The speaker outputs from the car stereo are H-bridge type, the return is not grounded but driven. Grounding any lead / part of it will eventually ruin the car stereo output amplifiers. The headphone jack is an even more exotic circuit. Float all the output terminals and just live with it.

not

If you only need to drive a headphone, you don't need the full power the brigde can deliver. What you can do is connect the each speaker "+" output through a electrolytic capacitor (+ to the output) to the L and R channel of the headphone and connect the common of the headphone to the *ground* of the radio (not to either "-" of the speaker outputs). This way, you only use half of each output bridge.

Meindert

About 8 ohms series with each capacitor. lowers the output a bit though.