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Thursday, March 1, 2012

Beware of Visseaux 6N7 failures

Hi!

I received several reports of Visseaux 6N7GT failing. Up to now 3 people who used these in my circuits had failures, one person had 2 tubes going bad, that is a total of 4 failed tubes.



This does not seem like a coincidence any more. I have zero reports of 6N7 from other brands going bad. I never used the Visseaux myself so I have no own experience with them. I'm just relaying what I hear from others. Failures happened in The Octal Preamp Mk1 and in two different power amps which use the 6N7 as driver tube.

Apparently they tend to develop heater to cathode shorts. In all my designs the voltage between heater and cathode is far below the maximum allowed. Also plate voltages and dissipation are within the allowed limits.

Those people who used the Visseaux all liked their sound a lot, but with these repeated reports of failures I'd discourage everyone from using Visseaux 6N7 in my designs.

Best regards

Thomas
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4 comments:

  1. MartyMarch 2, 2012 at 12:17 AM

    Hello Thomas,

    I use these tubes in the 6CB5A Amp for several month and didn 't have any problems. But the Visseaux 6N7s I have, have a white print label on the glass instead of the blue print shown on the picture. Maybe there is a difference in the time of production and maybe in the details of the construction.

    Best regards
    Martin

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  2. VinylSavorMarch 2, 2012 at 6:43 AM

    Hi Martin,

    The photo just shows a 6N7 from my stock. I do not know how the failed ones look like. The failed ones had been bought from different sources. The failures happened after several months or half a year of usage. I strongly recommend to remove them from your amp and to use another brand

    Best regards

    Thomas

    ReplyDelete
  3. MartyMarch 2, 2012 at 11:57 PM

    Hello Thomas,

    thank you for the advise, I will change the tubes. Meanwhile I have a little stock of 6N7 Tubes.
    I can' t hear a big difference between the 6N7 glass tubes with my gear, but this should not neglect the experience of the other who had this problems.

    Best regards
    Martin

    ReplyDelete
  4. UnknownSeptember 30, 2018 at 8:02 AM

    Personally, I employ plenty of Mazda 6N7 and Visseaux 6N7 tube in ST shape, whose internal structure is very similar. Up to now No fail happened to me pre-amplifier before. Never had I tried GT type before although I have some in my stock.

    ReplyDelete

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