Gustard H10 Mod 2 x Dual + 2 x Single SS Opamp
V5 OPA resulted in somewhat higher gain. applied -6db to amp to achieve roughly the same volume settings as stock. Biggest improvement noticed is in bass performance, HE-400i headphones lost their weakness in that area with this upgrade. Also modified amp final heatsink by adding case heat transfer block (work in progress).
Eric W.