Model: HPA-01a is the first release of the HPA series line. At this time, all of our resources are focused on perfecting this product.
In the near future, we will be offering this product with a tone control option, which will allow the user to adjust bass, treble, and mid-range according to their specific tastes. (This option is found only on a selected few Portable HeadPhone Amplifiers, let alone ones of this extremely portable size.)
We welcome you to check back with us from time to time to see what we may be offering down the line.
Gabriel, Stephane, George.