Bendix 6106 burn-in behavior

Thanks to both of you for your responses. Here's a little more information - 
The builder of my preamp has advised that the tube is faulty. Replacing the Bendix 6106 with the stock tube immediately eliminated the problem, and the seller has issued a complete refund.
Regarding the topic of burn-in, the tube originally functioned with no problems. I claim no expertise with respect to burn-in of this tube; quite the opposite. I had read on this forum another individual's experience with this type of tube in an earlier version of my preamp. I based my expectation on the need for burn-in on his comments.
However, the phono stage in this latest design is extremely resolving and that might mean that this tube is no longer a good match for the preamp. From here on out I plan to stay with the stock tubes.

In my correspondence with Nick he did not directly advise me or suggest that the 6106 was incompatible with the Cortese. But I do recall reading a post somewhere to that effect. But he doesn't call it out on his substitution list, so maybe that should have given me a clue. 

Correct - not a direct answer. But I will be following up with him on this and other similar questions.

BTW, don't underestimate the stock tube configuration. I think I personally had become somewhat infatuated with the idea of rolling tubes, and a subsequent experience has me wondering if what I heard was due to the way I had my cables dressed, because I experienced hum again, then remembered the cautions documented in the owners manual about the sensitivity of the preamp to nearby external sources of electrical fields. Re-dressing my cables eliminated that hum.