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Questions about tubes and gear that glows. FAQ

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Any dual, hi mu triode....

Posted by grhughes on May 25, 2012 at 09:24:45:
suffers from the manufacturing inequalities and difficulty of making a dual tube in one envelope that is well matched from side to side, ie both tubes, the same transconductance, mu, the same plate resistance, the same cathode current. They can't be made perfect, close but not perfect. Yes, there are differences from brand to brand. It was rumored once that the Chinese were evacuating tubes with foot pumps! I don't know if it was true but it came from a reliable American engineer that did consulting work for the wonderful Red Chinese. The best thing for an audiophile to do is get a transconductance tube tester and check the tubes for mu, ie gain, and distortion. Ray