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a single output transformerstereo tube amp ??

Discussion in 'Electronic Repair' started by Boborann, Oct 28, 2006.

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  1. Nope. In mono it is a parallel system. Only the stereo signal activates the
    split transformer which is probably much smaller.
    That would require one side to have an inverted signal. Where does that
  2. Guest

  3. Okay, I understand how you could be deceived, but you're WRONG, this is
    a stereo circuit.

    The way it works is:

    (1) The SUM of the left and right channels is amplified the usual way,
    with the output tubes being driven in push-pull, but CLASS A, so the
    average B+ current does not vary. That is important, as we'll see
    later on..

    (2) The DIFFERENCE is applied to the output tubes IN PHASE. This
    signal cancels out in the main output transformer, so it doesnt bleed
    into the main output signal, the SUM.

    (3) The difference signal, applied to the outut tubes in phase, shows
    up as current variations in the output transformer primary. That
    signal is picked up by the smaller transformer that is in series with
    the center tap.

    So we have in effect TWO separate class A amplifiers. The transformers
    do the magic of separating the in-phase and out of phase signals.

    (4) Then at the secondary of the output transformers, more magic. The
    secondaries are hooked up so that the difference signal gets added to
    one half, mathematically (L+R) + (L-R ) gives 2L, then in the other
    half, (L+R)-(L-R) gives 2R. Voila! Stereo!
  4. No. You have to step through its annoying process but it's only 30 seconds.
  5. Where does the inversion of one channel take place?
  6. robb

    robb Guest

    I wish all you gurus would figure this thing out i am intrigued and on the
    edge of my SEAT !

    when does the movie come out ?

    BTW isn't this just a version of a Williamson amplifier adding inverse
    feedback using the transformers for phase inversion to control the

    ( sorry for blurt , the intrigue forced me to break out my Buchsbaum and
    Douglas-Young books )
  7. Good question. I first assumed it happened somewhere in the tangled
    wiring in there.

    But I don't see it, so it looks like:

    (1) The left and right channels are kept separate all the way thru, up
    til the output transformer.

    (2) The Output stage isnt your typical push-pull-- because the plate
    leads are of opposite phase, what looks like the typical push-pull
    transformer, actually extracts the DIFFERENCE (I assumed the SUM
    before). The transformer in the B+ lead extracts the SUM current.
    Then the secondaries combine the signals in the usual stereo matrix L+R
    plus and minus L-R way. Very clever.

    The design isnt terribly super, as the channel separation depends on a
    close gain balance between the two paths. One weak tube and the
    channel separation goes down.
  8. Was there ever a single ended Williamson?
  9. Andy Cuffe

    Andy Cuffe Guest

    Does anyone have the original? If so, a scan that was high enough
    resolution to read and not mangled by jpeg compression would be nice.
    With the right kind of compression (GIF) the file would be much
    smaller and much easier to read.
    Andy Cuffe

  10. Jim Land

    Jim Land Guest

    No, it isn't. It dosn't even have a push-pull output stage (even though it
    looks like it does). As discussed above, there is no phase inverter stage,
    which is always necessary in a push-pull configuration.
  11. robb

    robb Guest

    well i dug up this williamson mod example schematic after you asked and it
    seems peculiarly similar ( to my untrained and unexperienced eye that is )
    pentodes for tetrodes and inductors for transformer and well no center tap
    on output transformer etc so i did notice some differences :}

    but you guys *obviously* know a heck of alot more than i do

    i am just chomping for the result even if i have to embarrass myself to see

    humbly rob
  12. robb

    robb Guest

  13. Sjouke Burry

    Sjouke Burry Guest

    Na... I just checked, it works, but they
    make dandy crossword puzzle access.
  14. Sjouke Burry

    Sjouke Burry Guest

    Yes, but has the designer been committed to
    an asylum ?
  15. Meat Plow

    Meat Plow Guest

    Bwaaaaaahahah my thoughts exactly.
  16. Guest

    Well, I'm getting webpage data now, and went through their bizarre
    routine twice, but each time it suddenly decides I want to upload
    instea of download, no dlwnload to be found anywhere. What a waste of
    time. What kind of bizarre mind created that site.

  17. Guest

    If you want to post the circuit somewhere accessible you';ll get an
    increased chance of it being all figured out. Or a bit more chaos :)

    Meanwile it sounds like the designer belongs where the retardedshare
    site designer also belongs.

  18. DaveM

    DaveM Guest

    To all who are trying to get a copy of the schematic in question: The OP
    posted it to alt.binaries.schematics, not to alt.binaries.schematics.electronic,
    the NG normally used by the electronics crowd. It's the only posting in the
    group at this time.

    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

    Some days you're the dog, some days the hydrant.
  19. robb

    robb Guest

    hi, i am not the orig circuit poster i just forgot a web link where i said
    "dug up this williamson schematic" my fix was i put the link into a reply to
    my reply, its a plain weblink to a GIF of a williamson schematic on antique
    amp page, i was thinking the OP stereo audio amp section looked like a
    williamson mod , i was challenged so i found a web reference.
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