I own a SX700, so I don't have a subwoofer output. But I was intrigued by your issue. I have been testing the Microsoft AI Copilot of late and figured I would ask it about your issue....
I own a Yamaha PSR- SX900 keyboard. When I plug in my headphone jacks the internal speakers mute as they should, but my subwoofer does not. Why???
Hello, this is Bing. I’m sorry to hear that you are having trouble with your subwoofer. There are a few possible reasons why your subwoofer does not mute when you plug in your headphones. Here are some suggestions that might help you solve the problem:
Make sure you are using the correct output jack for your headphones. According to the PSR-SX900/SX700 Owner’s Manual, you should use the PHONES jack on the rear panel of the keyboard, not the AUX OUT jacks. The PHONES jack automatically mutes the internal speakers, but the AUX OUT jacks do not.
Make sure you are using the correct input jack for your subwoofer. According to the [KS-SW100 Owner’s Manual], you should use the PHONE-RCA cable that came with the subwoofer to connect it to the keyboard. The cable has a stereo mini plug on one end and two RCA plugs on the other end. Connect the stereo mini plug to the SUBWOOFER OUT jack on the rear panel of the keyboard, and connect the RCA plugs to the INPUT jacks on the back of the subwoofer. The SUBWOOFER OUT jack automatically mutes the subwoofer when you plug in your headphones to the PHONES jack.
Make sure the volume of the subwoofer is not set too high. You can adjust the volume of the subwoofer using the VOLUME knob on the back of the subwoofer. If the volume is too high, you might still hear some sound from the subwoofer even when it is muted by the headphones. Try lowering the volume until you hear no sound from the subwoofer when you plug in your headphones.
What I am gleaning from this is that somehow the subwoofer jack/cable is unique and if not using the correct one it may not mute. Or the actual Yamaha SubWoofer is required along with the cable is required. I guess that is plausible? It does state it should mute, as your keyboard is new, Yamaha and dealer support should be available to you. In any case best of luck getting this resolved! And congrats on the new keyboard. My 700 is fabulous; your 900 is even more so.
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