HP stands for High Power . . . and HeadPhones! It’s easy to get more power from a tube.  Run it harder.  You will see claims of up as high as 100 watts from a pair of KT120’s.  Initially, the customer is happy.  More power is better, right?  Well … talk to the same customer in a year.  PrimaLuna amps are famous for long tube life, running cool, and being absolutely the easiest amplifier to own.  What we’ve done is increase the power and output transformer size, added another Adaptive AutoBias board, and all the supporting circuitry required to run eight power tubes instead of four.  Doubling the power and increasing bass slam.  Customers can use almost any tube on the market. EL34, KT88, KT120 and even KT150’s. The new headphone amp may be the best you ever heard.  Why?  It’s running from all the power tubes!  An elegant, well designed circuit allows you to switch from speakers to headphone as you wish.  Also if you love private listening, this amp will wow you!