It actually seems a bit random, but pretty easy to reproduce with the 42dBV attenuation enabled and 15-18dBV on the output, in loopback.
This is how I expect it to look:
In the screenshots above, left and right channel track each other pretty well with regards to THD.
Now look what happens next:
Suddenly the left channel has noticeably worse THD than the right channel.
I have not touched anything in the physical setup between the screenshots, or changed any of the settings.
On the Analyze page I can run measurements and the THD result will stay consistent, until I stop and press "Set" (with no changes to the settings). When starting measurements again, it might switch from the good THD to the bad THD, or the other way around.
So something happens when pressing "Set". Maybe the hardware state becomes inconsistent?
It's always the left channel. When it goes into a weird state, I tried changing the inputs, so the left output goes into the right input, and the right output goes into the left input. The result did not invert, the issue was still there on the left channel.
The issue also happens at lower attenuation settings, but the difference between the channels get smaller as the attenuation lessens. As can be seen from the amplitude sweeps it looks fine at lower output, and gets worse as the output increases.
When doing sweeps it also seems to get into the same state until it's finished. It will either be the good or the bad result.
I'm attaching 2 log files, showing the console output from the 2 different screenshots on the analyze page:
It actually seems a bit random, but pretty easy to reproduce with the 42dBV attenuation enabled and 15-18dBV on the output, in loopback.
This is how I expect it to look:
In the screenshots above, left and right channel track each other pretty well with regards to THD.
Now look what happens next:
Suddenly the left channel has noticeably worse THD than the right channel. I have not touched anything in the physical setup between the screenshots, or changed any of the settings.
On the Analyze page I can run measurements and the THD result will stay consistent, until I stop and press "Set" (with no changes to the settings). When starting measurements again, it might switch from the good THD to the bad THD, or the other way around.
So something happens when pressing "Set". Maybe the hardware state becomes inconsistent? It's always the left channel. When it goes into a weird state, I tried changing the inputs, so the left output goes into the right input, and the right output goes into the left input. The result did not invert, the issue was still there on the left channel.
The issue also happens at lower attenuation settings, but the difference between the channels get smaller as the attenuation lessens. As can be seen from the amplitude sweeps it looks fine at lower output, and gets worse as the output increases.
When doing sweeps it also seems to get into the same state until it's finished. It will either be the good or the bad result.
I'm attaching 2 log files, showing the console output from the 2 different screenshots on the analyze page: