Channel Imbalance vs Volume position

[DeLub]

Hi,

I'm looking for a headphone amplifier to get and have been browsing through the reviews. I'm just not sure how to interpret the channel imbalance graphs like below. I would assume that the RMS level would be a function of the position of the volume knob measured in the degrees of rotation. However, here it is a function of time. How should this be interpreted? 0 sec is max volume, and 17s is min volume? Would that mean that at 8.5s the knob is in 12 o'clock position?

 

[maverickronin]

IIRC Amir is just manually turning the knob down from max to min and recording the results.

I don't think even AP has a knob turning attachment to give accurate angles.

 

[Atanasi]

The graph starts at 0 dB, which is the maximum level. The red line represents the attenuation, the blue dashed line represents the channel imbalance. Channel imbalance is considered acceptable if it is within ±0.5 dB. The horizontal and vertical solid blue lines indicate the point where this tolerance is crossed, and then you can check the corresponding attenuation from the red line.

Please note that amplifiers like L30 and A90 have also negative gains, which I don't think are accounted in the graph. The well-behaving attenuation is therefore a bit more than the measured amount.

 

[DeLub]

Thanks for clarifying.