Thank you for suggestion. I tried swapping tube but the the left tube is always brighter regardless of which tube I use. I guess it could be an amp.   

Hi all,     I am really new to tube amp and just recently purchased the Wooaudio WA6SE. I really like the amp but I notice that two stock driver tubes do not glow equally.     The tube on the left side glows significantly brighter than the right one. I turned the amp off, waited for both...