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drdna wrote:

As I had been looking at all these tubes I began to also inspect their interior construction. This will amuse you: one thing I would do is to hold the tube right up to my ear so the glass would be touching and thus mostly damped. Then tapping the tube slightly would cause the internal cathode and anode to vibrate a bit, making a noise. There was a correlation between the type of noise and the sound the tubes in the stereo would make when music was played.

Years back what I used Lamm LP2 phonostage with notoriously microphonic 417A tubes I was doing something similar by maxing out volume, sticking the head into the horn and hitting the tubes with a little hammer with rubber coating. I was under impression that the character of noise and the decay of the nose would symbolize how good the tube was. Well, it did and did not. It helps to filter out the obviously bad tube but if does not helped to predicts how it might sound. Pay attention BTW that my methods was using hot tubes, not the cold tubes. If you feel that you are able to get the correlation between the type of noise and the sound then it is fine but I feel that it is more contrived self-convincing. I do clear remember the I had some tubes that did not have the lower noise (they were passable though) but they sounded the best. I think this method is OK to filter out the tubes of the same make (brand, type, vintage) but I think it is worthies if you try to compare the resonating noise of the tubes that have even slight construction differences.

drdna wrote:

I don't have a circuit built now for the 6E5P, but I have a bunch of 6E5P & 6E6P tubes. Based on my examining them I was guessing that the 6E6P should have slightly more "clean & neutral" sound than the 6E5P. I was curious if this was the case, so I thought to ask you, since you have a familiarity with both tubes.

You can make what I did. I made a small adapter that cross wires and convert 6E5P into 6E6P. Then you can plug in your tube socket whatever tube you wish. BTW, the 6E5P and 6E6P have in a way a unique construction that has a lot of to do with the way how Russians shaped in this tube the profile of electron cloud. The 6E5P and 6E6P were reportedly made to completely eliminate the Dynatron effect. I do not know or they did or not but the spaces in there are atypically huge, it is a fact. I have no idea how all this affect sound but I like how it sounds. Plug it in and you will hear it yourself.

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