• RE: WAF direct coupled integrated Push Pull amplifier - Ejam 21:24:22 02/19/14 (1)
  In Reply to: RE: WAF direct coupled integrated Push Pull amplifier posted by fiacono@optusnet.com.au on February 17, 2014 at 16:07:52

  Frank
  
  A few questions, if I may. First, can you detail your modifications to the PP2C cascode front end, and second relating to the PP2C cascode, doesn't this have enough gain to drive your kt120 output stage? Mine puts out 160V pp without breaking a sweat.
  
  Regards
  
  Anthony
  

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  • RE: WAF direct coupled integrated Push Pull amplifier - fiacono@optusnet.com.au 22:11:54 02/20/14 (0)
    In Reply to: RE: WAF direct coupled integrated Push Pull amplifier posted by Ejam on February 19, 2014 at 21:24:22

    Hi Anthony,
    
    PP2C Changes were only minor.
    I noticed a slight improvement using Gary’s BBCCS (must apply a higher –ve rail) cf the original CCS. I placed a variable resistor between the two cathodes and the wiper wired to the CCS for balancing purposes. I also discarded the coupling capacitors and wired the 6H30 plates directly to the KT77 grids. The KT77 were elevated to accommodate the higher Grid voltage similar to Kevin’s 6SN7 coupled directly to the 6BX7 drivers. This is how the current system is set up now.
    I also noticed an improvement using the LL1676 input transformer, which is my preferred option, other than for isolation etc.
    
    I did try driving the KT120 with just the PP2C but I required a preamplifier to get any decent volume. I was after a PP integrated amplifier with volume controls.
    Driving the KT120s with lower source impedance (LL1660S as 2:25:2) sounded better than the PP2C high output impedance driving the KT120’s. To be fair I also tested this with the PP2C directly coupled to the KT120’s, that required much higher voltages on the KT120’s.
    
    We all hear different things, sure other opinions will differ.
    
    Will be try voltage regulation in the near future.
    
    Hope I've answered your questions.
    
    Regards
    Frank
    
    

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• RE: WAF direct coupled integrated Push Pull amplifier - KevinC 05:29:17 02/19/14 (0)
  In Reply to: RE: WAF direct coupled integrated Push Pull amplifier posted by fiacono@optusnet.com.au on February 17, 2014 at 16:07:52

  I can see why your wife would prefer the first one over the second. Not too unreasonable...
  
  Seriously, I like very much the fact that the finished amp looks so good, but has the tubes mounted separately from the main top plate. That makes the amp somewhat future-proof, while retaining good looks. Well-executed and really good looking!
  
  How much does this expanse of metal weigh?
  
  Kevin Carter
  K&K Audio
  www.kandkaudio.com
  
  

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• RE: WAF direct coupled integrated Push Pull amplifier - D Mike 03:44:47 02/19/14 (0)
  In Reply to: RE: WAF direct coupled integrated Push Pull amplifier posted by fiacono@optusnet.com.au on February 17, 2014 at 16:07:52

  Remarkable! That's a great looking build. Love the pic of the proto board too.
  
  Congrats on an outstanding effort. WAF is hard to achieve in this hobby.
  

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