I contacted Mike of Headfonia.com a few months back to see if he’d be interested in reviewing the 627. He immediately told me that he was well aware of the Portaphile amplifiers but had never had a chance to audition one. I went over the design features of the amp and his first comment was, “did I understand you correctly, 4 hours run time? Is that a misprint?” and I responded, “Mike, that is not a misprint. I went on to explain that I have built the amp to maximize performance and while I can easily increase the runtimes by shutting down some of the performance features but it would be against my number one design goal, sound quality. For now, four hours is the best I can do. Please read the review and see what Mike had to say.