I sometimes use my QC35 headphones to listen to my turntable through a receiver using the aux cable and a 6.35 mm to 3.5 mm adaptor. I noticed that the sound is muffled when the headphones are turned off, but when it is turned on, it sounds fine. I don't have this issue when I use the aux cable with my phone. Has anyone else had this problem? What could be causing it?
Thanks for your post and welcome to the Bose Community. Hope that you're enjoying your QC35 headphones!
When the headset is powered on, proprietary Bose signal processing is enabled, which will adjust your audio experience with music that is played. The resultant output of audio will naturally vary between the range of devices that you connect the headset to and the connection method. In addition to this, many turntables may require a preamp to amplify the audio being output. This may be why when the headset is connected to a different device, they sound as expected when the headset is powered off.