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Question on NOS tubes bias doubt

I just put a New pair of NOS KEN RAD VT-231 in my CARY SLP-05 pre buffer stage, one for left and one for right, it sounds bias to the left for around say 10-15%, so I turn it off and swap them to confirm if it is not my room acoustic nature, as expected, it now bias to right for same amount. My question is, is it so called BIAS and that is why most tube gear has bias adjustment function? And should this be happening when seller says it is a matched pair NOS? I can compensate it with the balance feature on Cary SLP-05, but I doubt this pair is not matched. The testing figure in fact being declared slightly different while most of them are.
grandetech
larryken
537 posts
 
I don't understand your question but that's a real nice sounding tube.
rodman99999
6,128 posts
 
The Ken-Rads are some of the best VT-231's out there, but like anything else: They're not always perfect. You bought a pair of unmatched tubes. A slight mismatch shouldn't be noticable. That you have to compensate with a balance control says they're out quite a bit. Did the seller offer any satisfaction guarantee? BTW: Tube "biasing" is another story altogether(not related to your issue).
newbee
4,767 posts
 
If you are saying that the center image of your stereo systems drifts substantially with these two tubes that they must not be matched, despite what you have been told, I agree.

In fact I would suggest that not only were they not matched, but that the weak tube is close to dying. IME, other than an onset of noise or dullness, drifting is the hallmark of a tube which is about to die. IME, perhaps there are other reasons of which I'm not aware. I do not use this tube type.
grandetech OP
73 posts
 
Both Rodman9999 and Newbee understand exactly what my problem correctly, yes the image shift to one side 10-15%. Thanks for answering all my question precisely and confirmed. Now I have faith to speak with the seller and he sounds pretty responsible, I will post what the outcome is for future case reference to other members.
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