The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    Herb Keroes, David Hafler and the emergence of the Dynaco "Ultralinear" amplifiers

    Share

    Bob Latino
    Admin

    Posts : 2413
    Join date : 2008-11-26
    Location : Massachusetts

    Herb Keroes, David Hafler and the emergence of the Dynaco "Ultralinear" amplifiers

    Post by Bob Latino on Tue Jun 05, 2012 7:58 pm

    On May 20th, 1952 Herb Keroes and David Hafler applied for a patent (#2710312) on their new "ultralinear" output stage for tube amplifiers. The patent was issued on June 7th, 1955 and assigned to Acro Products where Keroes and Hafler worked. The patent description is below.

    Ultralinear output stage patent

    A lot of what was in the patent description is technical and difficult to understand. Keroes wrote up a short more easily understood description of the ultralinear output stage and its advantages in the pdf file at the link below.

    "Theory and Operation of the Ultra-Linear Circuit"

    Probably the first commercial amp to use the "Ultralinear circuit" was the Dynaco Mark II which came out in 1955 and was Dynaco's first product. All succeeding Dynaco tube amps like the Dynaco Mark III (1957), Stereo 70 (1959), Dynaco Mark IV (1960), Dynaco ST-35 (1963) and Dynaco SCA-35 (1964) also used the "ultralinear" output stage.

    Bob

    mrconclusion

    Posts : 15
    Join date : 2012-10-18

    Re: Herb Keroes, David Hafler and the emergence of the Dynaco "Ultralinear" amplifiers

    Post by mrconclusion on Sun Nov 25, 2012 5:39 pm

    Wow, that "Theory and Operation of the Ultra-Linear Circuit" booklet is really interesting. I can get really close to understanding the circuit they show at the end, which is saying something. Thanks for posting this it's very useful and educational.

    In the "Typical Quality Amplifier Design" diagram on page 21, does anyone know what are the two points marked "X" in the circuit? (between the two pentode cathodes)


      Current date/time is Thu Dec 08, 2016 9:49 pm