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RE: 6SN7 rolling.

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In Reply to: RE: 6SN7 rolling. posted by Tiberius on January 17, 2012 at 04:32:49

Im using a pair in a Bottlehead FPIII linestage. Pretty easy to hear differences between brands in general, Sylvania, RCA, Raytheon, GE etc. Not so easy, for me, to hear them within brand, atleast not tubes with similiar internal structure. My Favs' bang for buck are the Sylvania GTA's/GTB's, "chrome tops". I cant hear much if any difference between the angled or parallel "T" plate versions, GTA or GTB. Any differences between those "common" tubes and the more expensive VT-231 or brown base "W"'s are subtle to my ear and not easily described. And for me, not worth chasing more of them for the signifigantly higher price. The linestage is part of the headphone system at present. While I could settle in and be happy with many of the NOS tubes that I have (except for the Raytheons), there are definite differences between different manufacturers tubes that arent at all difficult to discern.

Follow Ups:

RE: 6SN7 rolling. - Tre' 15:18:58 01/17/12 (4)
If a circuit has gain stages without feedback of any kind it is easy to hear differences between 6sn7's.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
- RE: 6SN7 rolling. - Tiberius 06:35:27 01/18/12 (3)
  But are you hearing a real difference between tubes or just a change in operating point due to a slight difference in the tube operating points? My experience is that if you have 150 to 200 volts on the plate (not the plate supply) and an operating bias of 5 to 7 ma the differences between properly operating tubes is not audible. I can see it would be if you operate on the extremes or if you have tubes with widely different wear.
  
  I sat in on a local listening session a few years ago. The host had just completed a line stage. His workmanship left much to be desired but he did have a very nice listening room. He played a couple songs through his linestage, then switched tubes. The second tube was awful, with very high distortion and a compressed sound. Turns out he wasn't comparing like tubes, the point of his listening session was to show how much better a 12AX7 was compared to a 12AU7. Needless to say there was a huge difference, but it had nothing to do with the tubes, it was a matter of the operating point being at least OK for the 12AX7, but way too low for the 12AU7. So yes, he showed a difference, but it wasn't a valid test.
  
  The driver stage of my current power amplifier uses a 6SN7. I spent a good deal of time selecting the proper operating point for it. The 6SN7 is very consistant in the 5 to 7 mA range and as a result every tunbe I have tried biases to roughly the same point and I really can't say I notice any difference in sound between tube brands. I've been very careful to keep the volume level the same.
  
  Again, I'm not saying there aren't differences, I just can't confirm them. But honestly it seems like this huge difference between brands is largely fueled by people that sell tubes.
  - RE: 6SN7 rolling. - Laudanum 12:14:04 01/18/12 (2)
    Would there not be within spec differences between operating points of different tubes of the same tube brand and type?
    - RE: 6SN7 rolling. - Tiberius 13:02:15 01/18/12 (1)
      That is exactly what I think the "differences" really are. If you re-bias the tube to a different operating point the harmoinic content of the output signal will be different. The 6SN7 has a very large linear range compared to say a 12AT7 so it would have to be altered quite a bit but that could make for a very different response.
      
      All of the tubes mentioned control current in a vacuum through wire leads. I'm not sure what about that would result in such a drastically different sound, especially something like "more forward". There are differences due to manufacturing but again if you bias near the midpoint these differences are minimal.
      
      I belive you will find these differences to be orders of magnatude less than say the sound of different speakers.
      - RE: 6SN7 rolling. - Laudanum 14:16:00 01/18/12 (0)
        
        In Reply to: RE: 6SN7 rolling. posted by Tiberius on January 18, 2012 at 13:02:15
        
        My point was that I cant hear a discernable difference, for example, between two different pairs (same or similiar internal construction) of the same Sylvania 6SN7GTB's but I can hear differences between different tube brands. Surely the two different pairs of sylvanias would have different, within spec, electrical properties. No, not as vast a difference between tube brands as changing loudspeakers, but readily discernable differences nonetheless. I have to attribute this to sonic differences between the tubes themselves, not only due to different operating points which should still be within "spec" between properly functioning tubes of different manufacture.

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