From the looks of it we probably have the final release (based on SatoshiMatrix receiving another unit with the same sound issues). Unless Tofu can confirm that the final release has no hum/buzz what so ever, perhaps this is what we have like it or not. :/
I second the part about being grateful to Hyperkin, it's 16 years overdue but it's fantastic to have it here and we can only look forward to what comes next in this series and improved models in the future. Best regards to Tofu, his colleagues and everyone at Hyperkin!