Next, the A1 sounds a bit warmer than some other amps. I noticed this especially in comparison with the Grace m902 when listening to the Sennheiser HD800s. But, and this is a critical caveat, you need to read my to really understand this. That’s because the A1 is a high output impedance amp (about 100 ohms), and such amps should sound different than low output impedance amps (like the Grace) on some headphones. On other headphones this difference will be minimal. So, I have to caution that this sonic attribute may or may not show up for you.
Finally, the A1’s treble region sounds a bit drier than that of some other amps. By this I mean that the amp exhibits a very small amount of grain on treble sounds, at least when used with some headphones. Through the Sennheiser HD800s, for example, I felt the Grace m902 headphone amp showed a little more treble “micro-smoothness” than the A1 did. That said, however, I found this difference less noticeable when listening through the T1, so some of this may be attributable to frequency response differences caused by the different amps highlighting certain specific attributes of various headphones.