SOLVED: My USB audio is stuck in MONO

[DrKev]

Like the title says, I'm stuck in mono for any USB audio devices. The built in speakers and headphone out are still stereo. I have two USB ports and I get the same result with both of them.

I'm running Mojave 10.14.6 on a 2012 MBP. I've got two audio devices, a Yamaha THR5 amplifier, and Roland Quad Capture.

At first I thought it was a Reaper issue, but then discovered it applies to any audio output, from Reaper, or web browser or media app but only through the USB devices.

I canot for the life of me figure this out.

Yes, I have been through the Audio Midi Setup, the system Sound preferences, and the audio settings in Accessibility preferences (it is NOT set to mono output there).

Even google is getting fed up of my searches for info.

Anyone got any ideas?

[DrKev]

190 views and no answer. I appreciate you all looking. If I find an answer I'll be sure to post it here for future reference.

[solger]

Originally Posted by DrKev

I've got two audio devices, a Yamaha THR5 amplifier, and Roland Quad Capture

At first I thought it was a Reaper issue, but then discovered it applies to any audio output, from Reaper, or web browser or media app but only through the USB devices.

Can you post more details about how the entire audio signal chain (from input to output) looks like in this case?


Some general things that come to mind:

• Have you already ruled out a faulty audio cable or adapter?
• And for testing purposes: does creating and using an Aggregate Audio Device (https://support.apple.com/en-us/HT202000) make any difference?

[DrKev]

Originally Posted by solger

Can you post more details about how the entire audio signal chain (from input to output) looks like in this case?

There is nothing to tell you because I have stripped everything down to its simplest configurations and still have the problem.

I plug earphones directly into the MacBook, I have stereo.
I plug earphones into the USB devices, I have mono (summed L+R)

It makes no difference how they are connected: I usually have them both connected on a single USB hub but even if connected individually directly to the Macbook, via either of its USB ports, the problem still exists.

Yes, I have ruled out faulty cable.
Yes, I have tested each device separately and within aggregate audio devices.

[solger]

Originally Posted by DrKev

I plug earphones directly into the MacBook, I have stereo.
I plug earphones into the USB devices, I have mono (summed L+R)

What's the model name of the earphones that are connected to the USB devices?
And just to clarify: was using the same earphones on these USB devices working fine before?

If you're using an adapter to connect the earphones to the USB device: have you also already ruled out a faulty adapter? Or that the earphones are perhaps accidentally used with a mono adapter?

And for testing purposes: is the issue the same when listening, for instance, through the main outputs on the Roland Quad Capture (connected to speakers or another device) - instead of using headphones?

[DrKev]

Originally Posted by solger

If you're using an adapter to connect the earphones to the USB device: have you also already ruled out a faulty adapter?

And for testing purposes: is the issue the same when listening, for instance, through the main outputs on the Roland Quad Capture (connected to speakers or another device) - instead of using headphones?

THAT's IT!

FAULTY HEADPHONE ADAPTER!

I don't normally have external speakers connected, but as soon as I did they worked perfectly. Either, *only* the headphone outs on both devices were affected (not possible), or it was a headphone issue.

For the last 30 years, either as a musician or scientist, I have been teaching people that the first rule of troubleshooting is "physically verify ALL the stupidly obvious stuff FIRST".

This will be yet another good teaching moment.

THANK YOU, SOLGER! Your assistance is greatly appreciated.

[solger]

Great to hear that the mystery is solved