The 5U4GB rectifier tube is the Mack-Daddy of 5U4 valves and our tube of choice in the production of all new Mesa amps featuring this tube Based upon classic 1950’s technology, the 5U4GB is a new and vastly improved 5U4 design that is extremely reliable and consistent, as well as much more compact - It is basically the size of a 6L6 power tube, so please take special care to install them in the correct tube position(s), especially when replacing
6L6’s at the same time - This tube produces a “traditional vintage sag” with the most elastic and compressed feel of the two 5U4’s that we offer - Amazing feel and exceptional overall quality make this our factory favorite