If your B+ is over 550 volts buy NOS
These are okay in Ampegs, but I have to use real 7027As in my Evans, Sho Bud and other clean loud amps. A real 7027A should take 650 VDC B+ no problem. 600 VDC is the plate design max for a 7027A. This is more like a 6L6GC than a 7027, and not at all like a 7027A. Anyone who has taken a hammer to JJ tubes will find a few interesting things. The glass envelope is well made. The plates are okay, but the 6L6, 7027, and EL34 all have the same cathode. JJ tubes have a reputation of being quite tough, when you get a good batch. Unfortunately the quality is inconsistent. They drive my to fits of rage a few times a year. At least this seller and another seem to cull out the weird 6L6GCs that draw oddball plate currents. My local supplier was using a Maxi Matcher, with no regard to anything but matching pairs. They make some fine tubes, but this is not one of their better ones. I wish Tung Sol (New Sensor) would do a genuine 660 VDC absolute max 7027A!