My music source is a Jolida JD-100 CD player which is running a pair of Tungsol 12AX7 tubes in the output stage. The Jolida has a decent MOSFET headphone amp built in, but I felt that to get the best out of my Focal Elears I needed a dedicated headphone amp. A Matrix M-Stage HPA-1 headphone amp served the purpose well in that its neutrality maintained the characteristic warmth of the tube output stage without breaking the bank. I felt that this was a good base with which to try a serious replacement for the OPA2134PA. I replaced the Op Amp with a Burson V6 Vivid Dual and immediately noticed that the bottom end seemed tighter and more extended without having an exaggerated low end bump in the response. Mids appeared neutral whilst the smooth and controlled highs and seemingly improved separation contributed to a slightly more expansive sound stage. I’m confident that this is close to the best I can get out of the HPA-1 without stepping up to a fancy Burson headphone amp!