• RE: Lux91 monoblock running very hot - Henryhleung 07:03:42 07/19/13 (4)
  In Reply to: RE: Lux91 monoblock running very hot posted by Henryhleung on July 18, 2013 at 08:44:14

  Incidentally, while on the topic of 300B plate voltage..
  
  Thorsten, is it possible to lower the operating point of the Lux91 tubes? Ie reduce the voltage from 400v to 350v? I'm curious whether this would not stress out the tubes as much and increase the life of the 300Bs. Would this be possible with the Lux circuit and would it require much modification. Sorry if this is a newbie question or if I'm not making sense.
  
  The reason for asking is because people are often surprised or disbelieving when I tell them my mono blocks are rated 16w. Some reckon its impossible for a single 300b implementation, others say my tubes will burn out very soon. I've read your previous posts about 300b suggested operating points being conservative. But any idea how much more quickly the tubes will be eaten up in the Lux91 implementation?
  
  Thanks
  Henry
  
  

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  • RE: Lux91 monoblock running very hot - Thorsten 11:59:05 07/21/13 (1)
    In Reply to: RE: Lux91 monoblock running very hot posted by Henryhleung on July 19, 2013 at 07:03:42

    > is it possible to lower the operating point of the Lux91 tubes?
    > Ie reduce the voltage from 400v to 350v?
    
    Not really.
    
    > I'm curious whether this would not stress out the tubes
    > as much and increase the life of the 300Bs.
    
    Run at 300V/60mA the 300B should do 40,000 Hours, the way it runs in the Lux 91, around 10,000 hours. At 350V/80mA,the increase in live might be to 15,000 Hours, tops.
    
    > The reason for asking is because people are often surprised
    > or disbelieving when I tell them my mono blocks are rated 16w.
    
    The standard operation of the 300B at 400V/80mA will give around 12 Watt.
    
    http://www.westernelectric.com/products/300b_graphs.html
    
    The rest is due to the driver circuit, being able to produce a greater input voltage to the 300B than the datasheet uses... Think of it as either turbo or afterburner.
    
    > Some reckon its impossible for a single 300b implementation,
    > others say my tubes will burn out very soon.
    
    It is both possible, nor will the Amp "eat tubes".
    
    If you look at the above link, you will find that WE lists operation with even nearly 18 Watt output power (more than the Lux 91 manages).
    
    Of course, the tube experiences more stress and will live less long, but it is not a huge difference.
    
    
    Ciao T
    
    Sometimes I'd like to be the water
    sometimes shallow, sometimes wild.
    Born high in the mountains,
    even the seas would be mine.
    
    (Translated from the song "Aus der ferne" by City)
    
    

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    • RE: Lux91 monoblock running very hot - henryhleung 08:46:40 07/24/13 (0)
      In Reply to: RE: Lux91 monoblock running very hot posted by Thorsten on July 21, 2013 at 11:59:05

      I see.. thank you. If my 300Bs can last 10,000 hours I'm happy enough.
      

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  • RE: Lux91 monoblock running very hot - henryhleung@yahoo.com 01:19:40 07/21/13 (1)
    In Reply to: RE: Lux91 monoblock running very hot posted by Henryhleung on July 19, 2013 at 07:03:42

    
    
    

    
    Have any other Lux91 owners experienced this?
    
    Looking inside the mono blocks...
    
    The left monoblock (i.e. the hotter one) has some brown goo / residue over the two chokes. I think those are the two reactive interstage chokes. It looks like leaking liquid.. There's also a little amount splattered in the chassis. The liquid is hard - a wax-like substance? Could this be related to the heat problem? See image below.
    
    However, I also checked the right monoblock which doesn't run as hot, the chokes also exhibited some leakage although not as much as the other amp.
    
    Still waiting for the multimeter to arrive so haven't taken the measurements yet. Will report back when measured.
    
    
    
    
    
    

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    • RE: Lux91 monoblock running very hot - Thorsten 11:49:53 07/21/13 (0)
      In Reply to: RE: Lux91 monoblock running very hot posted by henryhleung@yahoo.com on July 21, 2013 at 01:19:40

      Hi,
      
      The residue is from the vacuum impregnation of the parts, they are basically dunked into a lacquer under vacuum to drive out air. When taken out the lacquer drops...
      
      This is how they look new... ;-)
      
      Ciao T
      
      Sometimes I'd like to be the water
      sometimes shallow, sometimes wild.
      Born high in the mountains,
      even the seas would be mine.
      
      (Translated from the song "Aus der ferne" by City)
      
      

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