MacBook sound balance changes on its own

I don't know what causes this, but I found and use https://www.tunabellysoftware.com/balance_lock/ which is free software to reset the balance when it goes off.

Had the same problem, when I centred the audio then changed volume it would drift to the right. I found going into the Audio Midi app, choosing the correct 2 channel audio out source (what ever the name of your headphones are but not the mic channel if you have one), change the format to 1 channel 16-bit integer, then change it back to 2 channel 32-bit again. After this the audio remained balanced.

This happened while using a PHL 45bu6900ch monitor via USB audio.

Solution: reboot your mac while having the correct volume balance in system settings

system settings volume balance

This is much rather a workaround. It seems it is resetting the balance falsy when changing the volume. However resetting it to center is what we all want (99,999%). Be aware that the issue might reoccur.

Furthermore my balance was altered in different ways depending on how I changed volume.

1. Using media buttons on keyboard -> Balance jitters around the center, not really noticeable, but you can see the slider jitter
2. Using volume slider in the top bar -> It immediatly resets the balance to the "default" ( value of balance during last shutdown) volume slider in top bar
3. Using the volume slider in system settings -> balance is not altered

I have never seen such an misbehaviour from apple products... This is almost microsoft quality 🤪

I've noticed that this will only happen when playing sounds from two different audio sources, such as two browser tabs playing sound simultaneously. I'm not sure as to why this is but I figured out that this was the cause in my case.

I suspect it's using the volume and balance from when it was last shutdown. My understanding is that, to change the volume of the power-on sound, you set your volume to the desired level, then use the GUI to power the macbook down. Doing that sets the volume in NVRAM so it knows what volume to use on bootup. It also likely saves other sound settings such as balance.

If you're like me, you seldom power down your macbook, preferring to use sleep or hibernation instead. You probably last powered it down via the GUI when your balance was off-center, and haven't done it since you replaced your headphones so it's still using that setting.