It is not, though I have a few of the 5Z4G tubes as well. This is the second tube listed in dubstepgirl's rectifier thread. It is really, really good. I had the 5Z4G in for some time before getting a used U52 for about 150 bucks. At that price, I doubt it can be beat. And I start to wonder how much better a maxed WA5 would be than a maxed WA6. One of these days I'll make it to a meet and maybe get to see.
http://www.head-fi.org/t/694525/dubstep-girls-massive-5ar4-5r4-5u4g-rectifier-review-comparison-rectifer-tube-rolling-thread#post_10053310
Thanks for the info, I've never heard of the Brimar U52.
I often wonder myself about how much better a WA5/LE sounds compared to a WA6…maxed or not.
I actually liked the WA6 more than the WA6-SE.
If you ever get the opportunity to hear the 5/LE, please fill me in on your impressions.
I have a feeling we're going to be in some trouble for wondering about this.