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valve amp design

Discussion in 'Electronic Design' started by george-b, Aug 21, 2005.

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  1. george-b

    george-b Guest

    can anyone send a circuit diagram for self build power amps using
    valves.Thankyou George Black.
  2. Edward Rawde

    Edward Rawde Guest

  3. Jamie

    Jamie Guest

    push pull using an output transformer?
  4. Robert Baer

    Robert Baer Guest

    How about a transformerless output?
  5. Philips/Mullard produced one in the late 1950 or early 60s. I think it
    needed a 120-ohm speaker.

    I don't believe it was ever published as a project in any of their
    amplifier designs books, but an outline of it was given in one of their
    training manuals. It looked as though the circuit was taken from one of
    their contemporary commercial hi-fi amplifiers.

    I can't remember the name of the book but I'm pretty certain the authors
    were Nijsen, Schobemma and Slot.
  6. Joerg

    Joerg Guest

    Hello Robert,

    Is "valve" rightpondian for "tube"? (hold the tomatoes...)
    We did one when I was a kid and had less respect for what 900VDC could
    do. Rewound a speaker coil on one of those monster speakers and that was
    no fun at all. Then we placed large labels onto the wires, warning
    everyone to never ever mess with these. The first twang on that E-guitar
    was phenomenal. We thought the rafters would come crashing down.

    Oh, and since a transformer was way over budget we opted for a
    "transformerless power supply". Three cascades from 230V and huge
    capacitors so we had enough oomph. In fact so much oomph that we could
    trip a 230V/16A circuit breaker.

    Regards, Joerg
  7. Robert Baer

    Robert Baer Guest

    What i meant was no capacitor coupling to the speaker, and use of a
    stadard 8 ohm speaker.
    The directly related patents are:
    C.T. Hall Mar 1955 #2,705,265 (filed June 1951)
    J. Futterman Dec 1956 #2,773,136 (filed July 1953)
    R. Karsten Jan 1988 #4,719,431 (filed Apr 1986)
    R. Karsten Jun 2001 #6,242,977 B1 (filed May 1999)
    And it is fun using the new design, touching the plates and ground -
    and feel zilch.
    And a gas, unplugging a tube or three while operating - and having
    zero problems.
    The "classic" Futterman design was a bitch to operate and caused a
    lot of bad ingrained ideas as how bad OTL "is".
    Modern OTL is very stable and robust.
  8. No tomatoes, but just a clarification:

    The word 'tube' is used in the UK to mean a CRT, the picture tube of a
    TV or a computer monitor. 'Valve' is a thermionic device for
    rectification or amplification (remember when they didn't used to be

    I'm sure you all knew that anyway.
  9. Joerg

    Joerg Guest

    Hello Adrian,
    I remember that from my days in Scotland. Turn on the tube or "telee".
    After that, hoover the carpet. Then off to pub (pronounced something
    like "poub") for a few pints of McEwan's Heavy. Ah, the good times.

    My first tube looked the shape of a Russion Babuschka. The others were
    actually all tubular, including the steel ones.

    Regards, Joerg
  10. Fred Stevens

    Fred Stevens Guest

    Try the book by the late John Linsley-Hood:

  11. Joerg

    Joerg Guest

    Hello Fred,
    Thanks. Interesting. But I was more into RF gear in my tube days. Big
    tubes. I grew up with tubes because they were available for free when I
    was a teenager. Discarded transistorized TVs showed up much later and
    then I could lay my hands on hotrods like the AF126.

    Audio tube amps presented in the electronic magazines were often a
    disappointment. To me 10 or 20 watts wasn't anything to write home
    about, we could build that with a few 2N3055 in those days. The monster
    tube amps that some of us built had to be calculated from scratch. The
    only reason the kilowatt range could hardly be cracked was that the
    typical circuit in Europe had "only" about 15 amps. One chord on the
    guitar and the lights went out.

    Regards, Joerg
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