This amp is a great amp. However, if you change OPA AMP to OPA 627, it will become a more amazing amplifier. However, please note that opening the lid may void the warranty. The resolution of the sound is high in the entire range from the treble to the bass, and changes in the triangle sound and small sounds such as the sound of playing the bass can be heard well. The bass is tight and powerful. It's a really great amplifier.