• Re: 1660 Load question - KevinC 08:51:53 10/07/03 (0)
  In Reply to: 1660 Load question posted by TomWh on October 06, 2003 at 22:23:26:

  Tom,

  The coil resistances are on the datasheet. But, as it turns out, you don't really need them. In your circuit the primary winding (which you can view as a choke) acts like a very high resistance (for AC), which implies a horizontal AC load line fixed at the plate current that you have chosen to operate the tube at.
  
  Kevin Carter
  K&K Audio
  www.kandkaudio.com
  
  

  ---
• Re: 1660 Load question - Tre' 07:58:08 10/07/03 (3)
  In Reply to: 1660 Load question posted by TomWh on October 06, 2003 at 22:23:26:

  The LL1660 will reflect, according to the step up or down way you hook it up, the impedance across it's secondary. If you don't have any grid resistors on the output tubes, the impedance presented to the 5842 will be very high (maybe in the meg. ohm range?).
  AFAIK this is one of the main reasons for using interstage transformers, horizontal load lines.

  Have Fun and enjoy the Music
  "still working the problem"
  Tre'
  
  

  ---

  • Re: 1660 Load question - TomWh 06:17:08 10/08/03 (2)
    In Reply to: Re: 1660 Load question posted by Tre' on October 07, 2003 at 07:58:08:

    I have a bit confused about how this circuit works. I put a DVM on the plate and the cathode with the amp playing music. They both remained constant. If the current remains constant with a horizontal load line I can understand the cathode remaining constant but B+ on the plate should change or where is the gain.

    It is my understanding that in a typical gain circuit the grid controls the current and resistor controls the voltage. Or the grid is like a solenoid allowing a lot of current flow for a small voltage change and then the resistor causing a voltage swing because of the increased current.

    Thanks Tom
    
    

    ---

    • Re: 1660 Load question - Jim Doyle 11:36:41 10/11/03 (0)
      In Reply to: Re: 1660 Load question posted by TomWh on October 08, 2003 at 06:17:08:

      
      A DVM is too slow to observe these changes.

      The way it works is as follows.. The tube is a transconductance
      device. The amount of current flowing through the tube is a
      scalar multiple of the grid voltage applied by the input signal.
      This scalar multiplier is... the transconductance. :)

      The changing current through the tube must pass through
      the primary winding of IT since the circuit is wired in
      series. The varying current in the primary induces a magnetic flux
      which is coupled to the secondary winding. Induction is the effect
      that describes the voltage potential developed on the secondary as
      a result of current change on the primary.

      It's basic electromagnetics... However, the design of these transformers is FAR from simple. The materials alone, as well as
      capacitance developed as a result of coil wire, insulation and
      layering make transformer design a field of expertise in its own
      right.

      Your project should work very well and sound REALLY good! :)

      I tried my LL1660 driving triode-wired KT66 and EL34s.
      I used a 6N1P with the 1:1 wiring and fixed bias on the
      centre tape of the secondary. My 1660 is presently in service
      in an 845 low volts amp right now. I'm considering buying
      another pair of 1660S/PP, gutting my ST-70 chassis one mo' time
      and turning it into "poor mans Amity": 6A3s, the original Dyna
      OPTs, LL1660s driven by ECC99 and CCS. Probably Edcor 10K:10Ks
      as input transformers for balanced line input.

      I'm beginning to think that phase splitting at the source is
      how to do things, and making the source output be really low
      impedance...

      -- Jim
      
      

      ---
    • use a scope - Tre' 19:37:24 10/08/03 (0)
      In Reply to: Re: 1660 Load question posted by TomWh on October 08, 2003 at 06:17:08:

      The voltage at the plate is 'moving' opposite to the grid.
      For some reason you're not seeing it with your DVM.
      You're statement
      It is my understanding that in a typical gain circuit the grid controls the current and resistor controls the voltage. Or
      the grid is like a solenoid allowing a lot of current flow for a small voltage change and then the resistor causing a
      voltage swing because of the increased current.

      is correct for a resistor in the plate circuit or a transformer.

      With a transformer, the load impedance can be higher than with a resistor.
      With a resistor, the larger you make it, the less power supply DC voltage you will have at the plate. With a transformer, it's DC resistance will be very low but at the same time it's AC impedance can be very high. The best of both worlds.

      I hope that makes sense to you...............Tre'
      
      
      

      ---

This post is made possible by the generous support of people like you and our sponsors:

Parts Connexion

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---