On ears will never be comfortable. No matter how good it sounds, it just pisses me of that I can't listen for a long time. placement is also a hit or miss. Overall, it's just a hassle. I settled with Sony WH-1000XM3 as my go to mobile headphone. It's got the sound, comfort and features to boot.
They are audiophile myths. These headphones are not as power hungry as they want you to believe.
Possibly due to HE-6 which is indeed very inefficient and power hungry, being made by Hifiman and a planar dynamic driver, has most audiophile misleadingly recommend high power amplifier.
The default gain for O2 is 2.5X and 6.5X. The output voltage remain the same(7V). Having more Gain is irrelevant if the max output volume is the same. It is actually bad because it means, you can easily drive the amp into clipping and channel imbalance at their worse.
Most people clip the...