Aune B1s Headphone Amplifier (Silver)

I have a stack of portable amps and this one stands out. It brings my Sennheiser HD 600 headphones to life. It’s almost as good as my plug in amps and a lot more convenient to use.

Maybe I received a defective unit. If not, it is seriously underwhelming.I used a galaxy S4 as a source and paired with in-ear Sennheiser momentum. These buds are extremely easy to drive and should have reached uncomfortably high volumes amplified. Instead, with gain set to low, overall volume was lower than with the phone alone even with volume maxed out on both source and amp. With gain set to high, I was able to boost volume above levels of Galaxy S4 alone but sound was distorted.I then tried my Audeze EL-8C headphones (the reason for the purchase in the first place). Again, no discernible volume boost except at max volume with high gain and high current settings which cause major distortion.I'm disappointed because the item seemed promising. However, in retrospect, there are no recent reviews available online for this item, the manufacturer's website isn't fully functional, and the specifications provided with the product do not match the specifications listed elsewhere on the web.