OTL Asylum

Posted by Angaria (A) on December 31, 2008 at 17:56:21

I'm currently building some line arrays with an active XO. My goal is to run everything off single-ended amps. Currently have a couple 2a3's, but I've heard several places now that OTL's can sound even smoother and more alive.

Is the transcendent SE OTL a good place to start, or is there some other SE implementation you would recommend? Wpc isn't really an issue because of the large number of drivers. Appreciate opinions.

• RE: FWIW - Ralph 09:04:45 01/02/09 (7)
  In Reply to: RE: SE OTL's - options besde transcendent? posted by Angaria on December 31, 2008 at 17:56:21

  Its the way the output transformer behaves in a Single-Ended amplifier that gives rise to the argument for single-ended. OTLs by definition have no output transformer, hence no argument for Single-Ended either.
  
  

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  • RE: FWIW - Peter H-son 08:33:22 02/22/09 (0)
    In Reply to: RE: FWIW posted by Ralph on January 02, 2009 at 09:04:45

    SE or not has nothing to do with transformers. Preamps are usually SE.
    
    I guess one of the things that OTL designs, tubes or SS, try to avoid is the DC offset of SE. Then there's the fact that SE is inefficient and OTL (tube) amps are already inefficient in PP.
    

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  • RE: FWIW - Tre' 09:13:05 01/03/09 (3)
    In Reply to: RE: FWIW posted by Ralph on January 02, 2009 at 09:04:45

    "Its the way the output transformer behaves in a Single-Ended amplifier that gives rise to the argument for single-ended. "

    Another argument for SE would be the lack of the phase inverter.

    There's no such thing as a perfect phase inverter.

    When two signals that are not exactly the same are recombined into one, some loss is incurred.

    It's the same argument against using parallel tubes. No two tube are exactly the same.

    Tre'

    
    Have Fun and Enjoy the Music
    "Still Working the Problem"
    
    

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    Edits: 01/03/09

    • RE: FWIW - Ralph 23:41:24 01/06/09 (1)
      In Reply to: RE: FWIW posted by Tre' on January 03, 2009 at 09:13:05

      The trick with phase inverters seems to be to use one that is effective. I've seen SE designs that use differential amplifiers. Since balanced is a much superior means of operating cables and signal sources, seems to me that having differential voltage amplifiers is a no-brainer- and there is no additional circuitry required.
      
      Any other method does seem to accrue a detrimental effect.
      
      

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      • RE: FWIW - WALLACE 05:33:27 02/26/09 (0)
        In Reply to: RE: FWIW posted by Ralph on January 06, 2009 at 23:41:24

        I think the trick is to go balanced from the start - I've done it by doing the phase inversion digitally and having two D to A's per channel.
        
        

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    • SE OTLs - Jim Dowdy 07:29:43 01/04/09 (0)
      In Reply to: RE: FWIW posted by Tre' on January 03, 2009 at 09:13:05

      I agree that phase inversion is a significant weak point.
      
      I've built two different SE OTLs and they sounded mighty nice.
      
      

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  • Great point, Ralph! - Lew 11:29:16 01/02/09 (1)
    In Reply to: RE: FWIW posted by Ralph on January 02, 2009 at 09:04:45

    You crystallized something that was vaguely bothering me about the concept of an SE OTL. Now I know what it was. In the Seigrfried, which DOES have an inductor on the output, I wonder how the output is configured to justify the "SE" appellation.
    
    

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    • RE: Great point, Ralph! - Ralph 17:12:58 01/02/09 (0)
      In Reply to: RE: Great point, Ralph! posted by Lew on January 02, 2009 at 11:29:16

      Seems to me the Siegfried uses David Berning's 'zero hysteresis' technology- the power tube drives an air-core transformer, which does the impedance conversion, and the energy is used to modulate a semiconductor AC power supply, which operates at low voltage/high frequency. I am of course putting it in a nutshell where it really doesn't fit, but the point is that that type of amplifier can be operated SE or P-P without particular advantage or disadvantage insofar as the output transformer is concerned, on account of it being an air-core.
      
      

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• RE: SE OTL's - options besde transcendent? - Lew 22:18:01 12/31/08 (1)
  In Reply to: RE: SE OTL's - options besde transcendent? posted by Angaria on December 31, 2008 at 17:56:21

  Try Berning Seigfried. I think it's SE, but I'm not certain. It may also be out of production.
  
  

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  • RE: SE OTL's - options besde transcendent? - Angaria 12:02:11 01/01/09 (0)
    In Reply to: RE: SE OTL's - options besde transcendent? posted by Lew on December 31, 2008 at 22:18:01

    Thanks - it does seem to be out of production, but the reviews are very positive. I'd be buying either of these used anyway - still in grad school.
    
    

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