A handheld product combining a high-segment DAC with USB front-end together with Nutube as the principal amplification stage. Provides full software controllability of all tube parameters. Feedback-less design offers the warmest, brightest acoustic sound, mainly intended for classical music listening, especially enhancing “basso continuo”. Entirely USB-powered for maximum portability. Conceived and designed by Dr. Ludovico Minati (lminati@ieee.org). Design materials available here.