Generally we have been using this one to good effect since it give a bit of extra juice to the hub: https://www.amazon.com/gp/product/B078MNW25Q/ (see the thread List of USB Accessories that work with Hypno
Generally we have been using this one to good effect since it give a bit of extra juice to the hub: https://www.amazon.com/gp/product/B078MNW25Q/ (see the thread List of USB Accessories that work with Hypno