I'm curious to know if manufacturers test the tubes that they use in the amplifiers before they ship them out? Maybe they test fine and then go bad within a month. I'm very suspicious they don't bother testing their tubes.
@emergingsoul They definitely test them! But there is not a good way to really know how long a tube will last, especially now in the twilight era of tube amplifiers.
Usually a tube amp producer will have a warranty on the tubes, which is usually 90 days. We do a year but that's unusual. So if you've had this amp less than 90 days I'd simply get a replacement tubes. If you own a tube amplifier its a good idea to have spares on hand. You can use a spare to help you sort out which tube is giving you trouble.