From: fiultra1@yahoo.com   
      
   On Thursday, December 8, 2016 at 3:20:48 PM UTC, boomer#...@none.com wrote:   
   > What is the most powerful audio output tube, as far as RMS wattage   
   > output?    
      
   There is a self-contradiction in this question. There are lots of really   
   powerful tubes but they aren't audio tubes; many sound like shit. There is,   
   even today, plenty of choice in quality audio tubes that sound great, but they   
   aren't necessarily all    
   that powerful. In hi-fi, furthermore, it is accepted that you sacrifice some   
   of the available power to operate the tube on the flattest part of its   
   transfer curve, so that mitigates against hogging out all the available power.   
   Also, the most refined    
   audio sound comes from triode tubes, which are pretty inefficient, meaning you   
   need lots or very big, not ones to make any appreciable power.   
      
   However, unlike some of the advice that you're getting here from people who've   
   never built or heard a big tube amp, there are ways to get around it. First of   
   all, you can parallel standard tubes like KT88 to your heart's content (well,   
   actually the depth    
   of your pocket, because the custom iron will cost plenty); I had a big OTL   
   KT88 amp built as a modular rack mount system that by rewiring would give any   
   output you wanted; it took up two bays; but it sounded like what it was, a PA   
   system. Even the humble    
   EL34 can build into a very potent amp: I got 96W of high quality audio sound   
   out of parallel push-pull tubes running in class A/B with toroidal trannies in   
   a stereo amp that two people could handle with ease, one with some difficulty;   
   for home use it had    
   18W in Class A, so the massive oomph was rarely needed.   
      
   Next, some of the broadcast tubes sound fabulous, for instance the 845   
   broadcast triode, and you can parallel triodes in single-ended output for the   
   finest sound of all, zero negative feedback SE, same as you can pentodes in   
   push-pull. For instance, my    
   80W SE amps were deliberately operated at only a fraction of theoretical   
   output to linearize the sound. I could as easily have chosen your 500W output   
   if I were willing to sacrifice some sound quality; instead I put the time and   
   the money into high-   
   sensitivity speakers.    
      
   None of this throws up insuperable technical problems. The biggest problem of   
   big amps is in fact the availability and cost of very high voltage connectors   
   for the separate components, or the monstrous weight if you build the thing in   
   one unit. For my    
   80W SE amp, Menno van der Veen designed the transformers for me, and Plitron   
   wound them, and listed them for the intrepid. But it is long since broken up   
   as too heavy, too hot, too large, too dangerous, just too unnecessary. The   
   booster amp, 3.8W of SE    
   300B, with a bicor horn turned out to produce all the sound pressure I   
   actually need. (A booster amp is a complete small power amp you use to drive a   
   much larger power amp.) Don't laugh. When a sports field across the street   
   from my house annoyed me with    
   their unshielded PA, I coupled my 3.8W 300B SE amp and bicor horns to the   
   stairwell in my four-storey town house, opened the front doors, and blasted   
   their premier event of the year into incoherence. They scrapped the offending   
   PA the next day.   
      
   ***   
   If you're just building a humongous amp to prove you're a swinging dick,   
   great, I admire initiative and balls and magnificent obsessions. But if you   
   have a real problem to solve, like x sound pressure in y spatial volume, I   
   suggest you redefine your need    
   working backwards from the speakers: if your speakers are sensitive, a Bessel   
   Array or bicor horns, the amp soon gets down to a practical size and   
   electrical requirement and the costs start approximating reality as she is   
   lived.    
      
   For a Bessel Array, try the brief introduction here:    
   http://www.audio-talk.co.uk/fiultra/JUTE%20on%20BESSEL.htm    
   And the smallest of my bicor horns looks like this inside:    
   http://www.audio-talk.co.uk/fiultra/KISS%20194%20T91HWAF3.jpg    
      
   Andre Jute   
      
   --- SoupGate-Win32 v1.05   
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