Had a fail in a power tube in a blues junior 3 after years of use with the stock tubes. Consider I am not changing tubes for any search for a different response or search of a tone in mind. Decided to buy these as they are pre matched plugged straight in no issues work really well. I cant say if they change the sound at all but I did reach for the bass knob and felt the need to add a bit more I am using a telecaster never the less they look and feel quality product and so far I am happy with them. Lets see if they last for years like the stock ones did. So in summary you cant go wrong for the money and the amp still sounds good after the install. Whats not to like consider though I am no cork sniffer in search of the golden imaginary tone I believe most of it is in the fingers anyway followed by the pick ups, nut and bridge material of the said guitar.