The original, early AC30s used Haddon power transformer, which was 285-0-285VAC at 117VAC.

The Hammond 290MX is shown as 275-0-275 and accounting for loading with a GZ34, you might expect 275 * 1.20-ish = 330VDC or so, probably less (more if your mains is higher than the primary at 120VAC). They should be running at 47mA and that's 118% of max. But you cannot run them at 350V plates and screens and expect the tubes to live long biased to 50R shared. That is how God and Dick Denney intended it to be. AC30s run and sound best with the EL84s at 120% of max diss. That makes the B+ run 30VDC hot unless padded down with a variac or other trickery. I have a 117VAC clone PT in my Blonde Bassman. You will get higher B+, higher plate and screen voltage, and even greater dissipation. wound for 110VAC, 117VAC mains of yesteryear) will result in a higher B+ than the original, vintage amp ran at. Running 121.5VAC into a 'vintage wound' power transformer (e.g. Pete's mains voltage 243VAC = 121.5VAC USA. Measurements taken with a calibration checked Fluke 189' 243VAC Mains feeding 245V PT PRIMARY, HEATERS 6.41VAC at the EL84s. 'The Woden in mine puts out 586VAC with the HT unloaded, 560VAC at idle, 560VAC at max clean 25W, 554VAC at fully overdriven square wave 38W. I saved this quote from Pete PFD64 (speaking about the power transformer):

Voltages are very important to get right with these amps and the devil is in the details. I've attached the specification sheets for the 290MX and NX.

Vox ac30 cc2 schematic