As promised, to update the post, this method along with a Furutech power cord has eliminated the buzz from every tube I've tried so far.
On a somewhat related note, received 6SN7 adapters today and have been listening since morning. To say the sound is disappointing is an understatement: slow, diffuse, opaque, no weight and slam, very weak lows, virtually non-existent highs, no chest on male vocalists, the impact of a feather. It's a sad state of affairs when a TV anti-oscillation tube kills my best 6SN7s in this circuit, and it only cost $5 a pop. The 6SN7 is the only tube type I've tried in this amp that a GZ34 had no positive effect on. I'm sticking with 6CY7s and a NOS pair of Philips 6FD7 fat bottles.
A RCA 6DR7 grey plate is the only tube I've found that makes the Brimar 5Z4GY sound half-way decent. In terms of clarity, detail, and dynamics with realistic timbre a #83V rectifier kills it. Hell, a CRC 5V4G actually brings most of the applicable frequencies to the table with power and scale behind them. A third the cost of the Brimar. Yea, the Brimar has a highly dimensional and spacious midrange, but that's it. Nothing else to offer. At least it's not as dreadful sounding as 6SN7s in this amp. I'm not thrilled after spending the money, waiting, only to be met with disappointment. Forgive me for being cynical, something tells me that some of folks recommending these tubes may not have heard them.