I have the Lyr 2 and used the HD 650 extensively on it, one that came in the new packaging. The stock tubes are a bit dull in the bass compared to the Voskhod Rockets I use. I never had problems with the bass, everyone who has tried my system always comments on how physical and powerful the bass is. But honestly it could be my DAC and cleaner power improving the bass moreso than the amp, I remember feeling quite mixed about the Lyr 2 after getting it, it sounded dull after my previous amp, the hyper Ef2A but I did recognize the amp sounded better. I do remember the newer HD 650 sounding brighter than the older pair I tried. Though it could simply be pad wear differences.