As with ALL tubes to be used in a phono stage, they need to be screened for noise and microphonics. There is no gaurantee that such and such brand will be low noise. There is going to be some variation in every batch of tubes produced. Some manufacturers put out better product than others; still you need to screen all tubes first, more so for a phono stage. I have purchased a VTV (vacuumtube.com)Dual Triode Tester that makes quick work of this. One can check gain of each triode, check triode balance and listen to each section of the tube being tested. Another option is to use your phono stage to screen them. If purchasing by mail I would get assurance in advance that the tubes could be returned for a refund if they prove to be noisey or microphonic.
