I was quite happy with the default AMP6 output stage on my iBasso DX150 (which is brilliant in and of itself), but got interested in a different flavour. I ordered the AMP9 and have been listening for a few hours now. The tube based output stage provides a very different lense onto the music, and the implementation of it I find simply delicious and done with taste and great integrity. I will spare you detailed descriptions of its sound characteristics, and of course appreciation may depend on individual taste (and set of headphones), but I find that this amp module is absolutely worth the invest if you're more of a pleasure seeker than a truth seeker when listening to music on your DAP. Splendid product!