I've been experiencing a strange issue where the volume in my monitors connected to the outs of my Apollo 16 mkII is drifting to the right speaker and then slowly drifts back to the center again and then back to the right over the course of 15 mins or so when I first start up. After a while, it seems to stabilize. I am using a MacBook Pro in Logic X with Yamaha HS7 monitors.
- I swapped the monitors, and the effect was the same: the left monitor loses volume to almost nothing slowly, then it comes back. The transition is always about 15-20 seconds.
- I swapped monitor cables, and the effect was the same.
- I swapped just the connection to each monitor, thereby swapping the L & R picture, and the effect was reverse: the right monitor lost volume instead.

All of that makes me believe there's an issue with my Apollo's stereo outputs. However, I haven't tested any of this outside of my DAW or with another daw. My headphone mixes are not affected at all. This is only happening with my monitor outs.

Any ideas?

Bumping this up. Just curious if anyone has any ideas.

Hi Graham,
this sounds like hardware issue. I can't easily imagine any common software or DAW issue, which can cause the problem. On the other hand, some failing cap at one channel (and associated temporary decrease of output level) will be more probable cause, according to gradual nature of that.

If you have free pair of physical outs, you can certainly try to connect monitors there and reroute monitor bus at console there. If you find, it's fine, then only main outs are affected. I don't know how often that happens, but if you want to have some proof for that (say for some RMA), then I would connect affected outputs back to inputs using some loopback cable, run some sine generator from DAW and record that back to another track.

I don't know, how old the interface is, but if you'll be sure, it's HW issue, I would try to apply warranty there.

Michal

Did you ever figure this out because my Apollo 8 Quad has the same exact problem!

I did! It was indeed a hardware issue. I contacted UA back in 2019 and sent in my unit for repair. It cost $155 plus shipping back to me. Below is what they shared with me from the repair notes. I hope it’s helpful!

“Summary - Service tech verified problem with unit reported.
Unit fail Monitor out Left channels intermittently
Cause: Bad PGA
Burn in test complete and unit retested. Unit passed all tests.
Parts - IC,PGA,PGA2311,SOL-16 - QTY -1 - $5.13”