This kit is for a Prosonic Head and includes a JJ GZ34 and a matched pair of JJ 6L6GC's in a cooler grade to get the Class A bias setting just right. The front end uses four ECC83S's with one balanced for the phase inverter in V4. Get a great clean & more definition in the drive channel.
All you need to adjust the bias on a Prosonic is a bias probe and a multimeter or the Eurotubes "Pro One". All of these are are available in the "Related Products" tab. You can use the "Generic JCM800" bias video for reference. While the Prosonic is quite different, the process and tools are identical. We typically bias Prosonic's in the A/B mode between 36 to 44mA with the JJ 6L6GC's. The bias pot is located inside the chassis. The video below explains the difference between bias probe types.