My QA490 seems to have gain mismatch between channels

1

Greetings,

I finally got some time to try doing IEM measurements on QA490 (previously I was only using it for impedance measurements of headphones). It appears to me that gains of left and right mic channels are differ by about 4 dB. To verify that I used the same IEM, coupled it with the first mic, saved FR as an overlay, re-plugged cable going to QA401 L+ input to Out R of QA490, coupled the same IEM to the right mic and adjusted it to make sure that the traces look similar. As you can see, they indeed look similar but shifted by about 4 dB:

L-mic-vs-R-mic-same-headphone
L-mic-vs-R-mic-same-headphone720×480 56 KB

This looks like a calibration problem with QA490 to me. Is there an easy way to fix it, without sending the unit back for calibration?

2

Hi @mnaganov, there’s not a calibration that could be readily applied and the match should be better than what you are showing here. I think your test is definitive–something is up. Can you please contact us at the support alias (below) and Jan will help arrange next steps.

image

3

Thanks @matt and Jan! After recalibration the measurements done by the left and right mics of QA490 are much closer. This is the same experiment on the recalibrated device:

L-mic-vs-R-mic-same-headphone-after-recalibration
L-mic-vs-R-mic-same-headphone-after-recalibration720×480 61.8 KB