• Gain vs. Dynamics - Kuei Yang Wang 11:55:30 10/12/03 (3)
  In Reply to: Line Stage Kit posted by pushpulltriode on October 12, 2003 at 02:48:23:

  Akwaaba from Accra Ghana,

  (instead of Konnichiwa from Londra)

  > However, I am a little bit concern about the dynamci
  > range this line stage can be reach based on the "5dB" of gain.

  I have come across this misconception many times. Gain and dynamic range have absolutely no relation, neither sonically nor electrically. Most systems have WAY too much gain, leading to good listening volumes being reached with the volume control at very low settings. This simply implies that most of the volume control range is unusable, not that there is ANY form of "headroom" that could be used by "turnmiong up the volume".

  In a well matched system you will find that the Volume control is nearly fully open with a good recoirding played back at realistic volume. This ensures best transparency and dynamics (subjectively and objectively), try it.

  I find line stages with 6db or no gain sufficient in most cases and they usually have better dynamics (percieved) than hiogh gain designs...

  Sayonara
  
  

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  • Congratulations!!! - Bas Horneman 05:55:23 10/16/03 (1)
    In Reply to: Gain vs. Dynamics posted by Kuei Yang Wang on October 12, 2003 at 11:55:30:

    May you and your wife live happily ever after. How was your wedding day?

    Greetings,
    Bas
    
    
    

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    • Re: Congratulations!!! - Kuei Yang Wang 23:58:59 10/17/03 (0)
      In Reply to: Congratulations!!! posted by Bas Horneman on October 16, 2003 at 05:55:23:

      Konnichiwa,

      Thank you for your kind words, it was great. I also managed to sort out my Wifes Visa problems, so she will be with me this week.

      Sayonara
      
      

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  • Re: Gain vs. Dynamics - C.Y. 08:58:11 10/14/03 (0)
    In Reply to: Gain vs. Dynamics posted by Kuei Yang Wang on October 12, 2003 at 11:55:30:

    Hi,

    I think I knnow what you are saying. My volume, normally indicated 12 o'clock. When excited for louder music, it is on 3 o'clock.
    Some people believe that loudest music(clipping beyond) at 9 o'clock indicates 'Power'..

    C.Y

    
    
    
    

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• Re: Line Stage Kit - Dave Davenport 11:29:07 10/12/03 (12)
  In Reply to: Line Stage Kit posted by pushpulltriode on October 12, 2003 at 02:48:23:

  Hello PPT,

  You are right, the 6N1P is an excellent tube for this application. I chose it after listening to many alternatives.

  The circuit is fully differential, input to output, and can be used with either balanced or unbalanced inputs or output. To interface with an unbalanced input or output simply ground one side of the transformer, so the gain is independent of whether the inputs and outputs are balanced or unbalanced.

  Most folks have way too much gain in their system and end up throwing it away in the volume control. The 5dB is a conservative number and I chose the design point to allow sufficient gain and at the same time provide a good range of adjustment of the volume control. I have never run it at full volume in my system; on the other hand I do not have to settle for a volume adjustment between 7 and 8 o'clock.

  Overhead is a design parameter separate from gain. Even if the gain were to be 0dB, you would need adequate overhead to handle the largest signal you expect to see. When used together with the associated Raleigh Audio power supply, I have been generous with the amount of overhead provided and made it easy to increase it further if needed.

  Dave Davenport
  
  
  

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  • Re: Line Stage Kit - pushpulltriode 22:30:46 10/12/03 (11)
    In Reply to: Re: Line Stage Kit posted by Dave Davenport on October 12, 2003 at 11:29:07:

    Hi David!
    > > The 5dB is a conservative number and I chose the design point to allow sufficient gain and at the same time provide a good range of adjustment of the volume control. < <

    If 5dB is a conservative figure, what is the maximum gain in the line stage?

    One more question would like to ask you. Have you tried the 274B rectifier tube in the power supply? I don't know which rectifier tube you are using but it looks like a 6X4 refer to the picture form your website.

    Will it be possible using 274B rectifier tube in this linestage? What about mono power supply?

    Regards,
    PPT
    
    

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    • Re: Line Stage Kit - Dave Davenport 10:22:45 10/13/03 (10)
      In Reply to: Re: Line Stage Kit posted by pushpulltriode on October 12, 2003 at 22:30:46:

      Hi PPT,

      There are two answers to the gain question.

      First, using the board as currently wired you could get an additional 3dB or so by eliminating the damping resistors on the secondaries of the transformers. About another 3dB could be gained by judicious choice of the resistors in the volume control.

      Second, you can change the wiring of the transformers. I dump 6dB on the input transformer and 12dB on the output transformer. There are provisions on the board to rewire the output transformer.

      So, all in all, just looking at gain, you could get about another 24dB or so on top of the 5dB for a total of 29dB, which is pushing the advertised approximate 30dB limit of the 6N1P. If you want more than that, you can change the tube you use.

      The power supply uses the 12X4, which is the 12V variant of the 6X4. I have not tried the 274B but if you design your own supply you could use anything that would provide a minimum of 250V at 40mA.

      You could uses a mono supply or split the single supply with series resistors to isolate the two channels.

      Dave
      
      
      

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      • Re: Line Stage Kit - pushpulltriode 03:47:49 10/20/03 (9)
        In Reply to: Re: Line Stage Kit posted by Dave Davenport on October 13, 2003 at 10:22:45:

        Dear Dave,
        Now I understand what you mean regarding the gain issue, and thanks for your detail explanation. I concern 2 issues that I forgot to ask last week because I just recover from a bad flu.

        1) In a push pull (differential) linestage, we have nothing to concern about the "crossover distortion" in RC coupling. However, it will be a serious concern in a linestage or preamplifier which is using transformer coupling in push pull all the way through due to the low level amplification, and a transformer (PP in and PP out) will causing crossover distortion. And I think it'll be seriously damage the low level detail. I might be wrong because the reality sometimes not really match with the principle, especially in audio world.

        I know another type of transformer coupling "Balanced" preamplifier, just like Tim de Paravicini's EAR 864; it convert the incoming signal to SE and the whole circuitry is done in SE amplification with feedback loop and transmit the signal to the output transformer. The output transformer has feedback winding, and convert the SE signal back to balanced output. This method has minimum crossover distortion but need feedback to lower the distortion. Do you think it is an opportunity cost between these 2 different balanced transformer coupling design:)

        2) How come you don't use the Steven & Billington TX102 at the input of the linestage? If using TX102, it will be no longer need the input transformer and resistive type stepped attenuator (the one right after the output of the input transformer). Do I correct?

        Finally, how big the coupling capacitors using in the linestage kit?

        PPT
        
        

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        • Re: Line Stage Kit - Dave Davenport 07:42:19 10/20/03 (1)
          In Reply to: Re: Line Stage Kit posted by pushpulltriode on October 20, 2003 at 03:47:49:

          Hello PPT,

          The crossover distortion that you talk about is a characteristic of the class of amplifier, class-A, Class-B, class-AB, and not the method of coupling. In a class-A amplifier, the tube is always conducting and never cuts off. This is necessarily the mode of single-ended amplifiers. In a push-pull amplifier, the designer often takes advantage of the fact that one side can supply all of the power while the other is cut off for part of the cycle. In class-B each side of the amplifier cuts off for one-half of the cycle while the other half bears the load. In class-AB both are conducting at low levels while one cuts off at higher levels. You could design a push-pull amplifier where each side operates in class-A and never cuts off, so each side is working all of the time contributing to the output. In my opinion the very best push-pull amplifiers are fully class-A. Believing this, of course I designed my Line Stage to be fully class-A so there is no crossover distortion. Think of it as two separate single-ended-triode amplifiers, each amplifying the opposite phase of the signal. A differential output (transformer primary) is taken from the plates of the two SET amplifiers.

          The TX102 is an excellent transformer and I considered doing exactly what you suggested. In fact, Lynn Olson and some of his audio companions have tried using the TX102 as an input transformer and phase splitter for a push-pull amplifier. They reported that there was a problem with balance between the two split signals. Therefore I have set that project aside for a while.

          There are no coupling capacitors, only a single parafeed capacitor. That capacitor was chosen empirically to provide the best frequency response. With a pair of 6N1P triodes driving an LL1674 I found that a 2uF capacitor was optimum.

          Dave Davenport
          
          
          

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          • Re: Line Stage Kit - pushpulltriode 08:56:32 10/20/03 (0)
            In Reply to: Re: Line Stage Kit posted by Dave Davenport on October 20, 2003 at 07:42:19:

            What about using Sowter 9335 transformer instead of S&B TX102 for the linestage kit?
            
            

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        • Re: Line Stage Kit - pushpulltriode 07:24:01 10/20/03 (6)
          In Reply to: Re: Line Stage Kit posted by pushpulltriode on October 20, 2003 at 03:47:49:

          Sorry my mistake! I mean using Sowter 9335 transformer not TX102 for the input of the linestage.
          
          

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          • Re: Line Stage Kit - wiligruen 08:57:54 10/20/03 (2)
            In Reply to: Re: Line Stage Kit posted by pushpulltriode on October 20, 2003 at 07:24:01:

            Hi,
            What about using the TX102 as output parafeed?
            
            

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            • Re: Line Stage Kit - Dave Davenport 10:28:10 10/20/03 (0)
              In Reply to: Re: Line Stage Kit posted by wiligruen on October 20, 2003 at 08:57:54:

              We have thought about this but have not pursued the ides. Generally, the transformer volume controls like a low input impedance and a high output impedance. The advantage of using the configuration that I am currently using is that it provides a low output impedance. I suspect that for an optimum design you would have to retain the LL1674 output transformer to feed the volume control transformer. And then, you would still have the higher output impedance of the VC transformer. As to how it would sound, you would have to build it and listen.

              Dave
              
              
              

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            • Re: Line Stage Kit - KevinC 10:03:51 10/20/03 (0)
              In Reply to: Re: Line Stage Kit posted by wiligruen on October 20, 2003 at 08:57:54:

              That is an idea that we have toyed with speculatively, but not tried. In principle I can see no problems, but maybe someone else who has tried it can comment.
              
              Kevin Carter
              K&K Audio
              www.kandkaudio.com
              
              

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          • Re: Line Stage Kit - Dave Davenport 08:55:28 10/20/03 (2)
            In Reply to: Re: Line Stage Kit posted by pushpulltriode on October 20, 2003 at 07:24:01:

            Hi PPT,

            Sorry but I have no experience with the Sowter 9335.

            Dave
            
            

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            • Re: Line Stage Kit - pushpulltriode 04:24:22 10/22/03 (1)
              In Reply to: Re: Line Stage Kit posted by Dave Davenport on October 20, 2003 at 08:55:28:

              Dear Dave,
              The following link from Sowter show the wiring of the 9335.

              Do you think it can be use in the line stage kit?

              Thanks again!
              

              • Sowter 9335 attenuator   (Open in New Window)

              
              

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              • Re: Line Stage Kit - Dave Davenport 08:21:35 10/22/03 (0)
                In Reply to: Re: Line Stage Kit posted by pushpulltriode on October 22, 2003 at 04:24:22:

                Hi PPT,

                Do I think there is any gold in them thar hills? Well, the only way to know is go and prospect.

                I see no technical reason that the Sowter 9335 wouldn't work, but how well it would work is the question. To find out you must build it and listen. I tried many transformers while developing the Line Stage and found the LL1674 to be the best. Of course I can't say that a better transformer does not exist, just that the LL1674 is an excellent transformer and by far the best of the ones I tried.

                Dave
                
                

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