There may be amps that have no issues with these tubes, but if your amp is sensitive to the type (manufacturer) then this may not be the tube you are looking for.

Again, I am sure that they would work well in other darker sounding amps or stereos--just didn't give me the 'wow,' that I wanted to hear.

Amp works good again but it sounds flat , no rich harmonics

Amp works good again but it sounds flat , no rich harmonics

turns a very good amp into a tone machine.

Out of a quad I purchased two were so microphonic, lightly tapping the guitar cable to the input jack caused my amp to ring like a chime.

Went from a good sounding amp to a great sounding amp.

I do alot of tube swapping and for my cheap little amp

My amp was not very humbucker-friendly with the stock tubes

Definitely sweetened up my Marshall hybrid practice amp.

With these tubes, I have no doubt these amplifiers are acting as good as or better that their impressive specs