They are incredible in tetrode in my system.
If they’re not good in your system in tetrode, you have something wrong.
It is also no problem to bias them.
If you have a multimeter & a screwdriver, it’s really simple.
Before the 450MKII were purchased I had VTL 300 Deluxe mono blocks. Great amps but tube faults were a major pain. With the 450's tube faults are a breeze. When a tube goes, it's identified by a flashing little green light. The power to the amp is shut, with gloves the tube is replaced, if a fuse went its also replaced. I'm up and running in less the 5 minutes. Auto Biasing between the notes of the music, come on now that's too cool.
Hi guys. Interesting thread about VTL and tube faults. I own a S-200 and experienced my first tube fault. Unfortunately, the fault will not resolve by replacing the tube that indicated the fault. I've followed the reset process to the t and it still indicates a fault with a flashing green light. Any ideas?