Posted by Lim on September 11, 2006 at 03:55:49

Hi there,

I have an old Ella based on the Consonance M100 design. Those of you who have this set will know that the kit only provided for one output connection; either 8 ohm or 4 ohm. I would like to know if anyone here have added an additional connection so that both 8 ohm and 4 ohm connection is available. Of course only one will be connected at any time. I think it is do able because I note that the Consonance M100 is fitted with both connections. What I like to know is how you do it. I am especially concerned about the connection to the main PCB. I hope someone answers.

Regards,
Lim
Georgetown,
Penang

• Re: Ella Output Impedance - zarniwoop 18:47:12 09/15/06 (2)
  In Reply to: Ella Output Impedance posted by Lim on September 11, 2006 at 03:55:49:

  hey,, im back!..or still here!

  With both 8 and 4 ohm speaker connectors you only need to hook one of them back to the PCB (this is for the global negative feedback loop). Usually this would be the 8ohm tap, wich gives slightly more feedback. The 4ohm just goes to the 4ohm tap of the output transformer.

  FWIW, i wired my OPT to use the 4ohm tap... always. So i connect 8 ohm speakers to the 4ohm tap. This sounds best to me, but is likely speaker dependant. (and I've disconnected NFB loop also)

  try for yourself, as usual
  enjoy,
  
  

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  • Re: Ella Output Impedance - Lim 00:50:34 09/16/06 (1)
    In Reply to: Re: Ella Output Impedance posted by zarniwoop on September 15, 2006 at 18:47:12:

    Hi zarniwoop,

    Thanks a million. I asked DIY HiFi and yielded nothing apart from an advice that I could install a switch at the back. You must really know this circuit well. I have several speakers rated at 8 ohm to 4 ohm. The amp already sounds good connected at 8 ohm and seeing your comments, I can't wait to try out the 4 ohm tap.But I don't understand about the global negative feedback loop. If I am going to leave this loop at the 8 ohm tap and I hook up the load to the 4 ohm tap; wouldn't I be leaving out this loop from the circuit? And why have you disconnected the NFB loop altogether? If it is not essential, why is it in the design in the first place? I am trying to make the modifications this weekend. I will be replacing all the binding posts with Eichmann CablePod. Expensive stuff but cheaper than WBT equivalents. Hope to hear from you again and thanks again.

    Lim
    The impoverished audio enthusiast
    
    
    

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    • Re: Ella Output Impedance - zarniwoop 11:51:40 09/16/06 (0)
      In Reply to: Re: Ella Output Impedance posted by Lim on September 16, 2006 at 00:50:34:

      If you leave the NFB loop connected only to the 8ohm tap it will still function with a load connected to a separate 4ohm tap. There is still a voltage across the full OPT secondary, and this is the source of the feedback signal (ie the speakers are not part of the feedback loop). The current for the speaker is then drawn from the 4ohm tap.

      I have disconnected the feedback loop only as a personal choice, since I have drastically modified the circuit from the original design anyway. If you want to keep it as designed, then leave it in. I found it unneccesary when the output tubes were triodes or triode-strapped pentodes. This is DIY, afterall, so I enjoy that freedom to customize it to my liking.

      Great amp platform, btw. Even after scratch building a SE 300B amp, I still love the Ella.
      
      

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