Fairchild 275 Pair on Auction site

Discussion in 'Dollars and Sense' started by multichamp12, Oct 2, 2017.

  1. radioactive

    radioactive tube gear fanatic

    Messages:
    8,276
    Location:
    winnipeg , manitoba
    I have a pair of N.O.S g.e.c kt77's that I one day want to do the 260 mod too but I still need another pair to go forth with. Until then I'm happily lisiteng to them with a original pair of Svetlana winged c 6l6gc's.
     
  2. Pio1980

    Pio1980 AK Member Subscriber

    Messages:
    22,027
    Location:
    Angel Station, Alabama
    There were a number of post-Williamson amps that used the big 6550 /KT88 outputs, the Dynaco Mk-3 probably the most numerous. I mentioned the Marantz Mullards because they were a touchstone standard in that era.
    Fwiw, some owners of multiple examples think the MC225 the best sounding McIntosh tube amp, and the Marantz 8/ 8B the alternative. The 225 is afaik the simplest McIntosh amp using the unity coupled output circuit.
     
  3. Sam Cogley

    Sam Cogley Last of the Time Lords Subscriber

    Messages:
    31,456
    Location:
    SW Missouri
    Fairchild used double C-core grain-oriented output transformers. Winding them had to be an absolute pain in the keister. I'm not sure that even McIntosh went quite so far out in their OPT designs. I'd love to see someone reproduce the Fairchild OPTs, but the cost would probably be prohibitive.
     
  4. x3workshop

    x3workshop AK Subscriber Subscriber

    Messages:
    1,819
    Location:
    Harlem

    This is said to be a McIntosh MC240 OPT core. Unverified.

    http://www.ebay.com/itm/Mcintosh-MC...686563?hash=item41d08ba3a3:g:aFwAAOSwv8ZZy-Rc
     
    Last edited: Oct 5, 2017
  5. Pio1980

    Pio1980 AK Member Subscriber

    Messages:
    22,027
    Location:
    Angel Station, Alabama
    Afaik, Todd made the OPTs for Fairchild.
     
  6. Sam Cogley

    Sam Cogley Last of the Time Lords Subscriber

    Messages:
    31,456
    Location:
    SW Missouri
    Indeed. This image was taken from an article in the November 1956 Radio & Television News. Note the transformer wound through a pair of C cores, rather than the single C core of that Macintosh 240 OPT. Also, note the byline.
    Fairchild-OPT_R&TN_11-56.jpg
     
    Crestwood23 likes this.
  7. Pio1980

    Pio1980 AK Member Subscriber

    Messages:
    22,027
    Location:
    Angel Station, Alabama
    I've seen similar construction in German xformers, single sided. I recall other examples of both constructions and am not aware of the practical advantages.
    How were the UTC LS series done?
     
  8. biscuithead

    biscuithead Me likes the eargasm retroplasm... Subscriber

    Messages:
    3,193
    Location:
    Northern Colorado
    What are the advantages of the double C-core?

    I sort-of understand eliminating the switching transients with McIntoshs' 1947 development of the "unity coupled" transformers... But how does the Fairchild/Todd transformer keep thd below 1% at 75% of rated power? I think, (If I'm not mistaken) that the Mac Trannies of the same time period have quieter numbers, but I admit that the specs are very close in the lions share of the curve.

    I've read this ( http://www.vt4c.com/teach_room/choose_transformer.html ) and my tiny mind is having a hard time understand the advantages of the double C... It is obviously twice the manufacturing time... is it Magnetics, harmonics, or just a cleaner amplification method?

    I also found this video where Gordon Gow is explaining the Unity Coupling on the Mac Tranny-
     
    Pio1980 likes this.
  9. Sam Cogley

    Sam Cogley Last of the Time Lords Subscriber

    Messages:
    31,456
    Location:
    SW Missouri
    It would be interesting to see some side-by-side evaluations. Obviously the guys at Fairchild and Todd thought it was worth the extra expense for an all-out amplifier.
     
  10. x3workshop

    x3workshop AK Subscriber Subscriber

    Messages:
    1,819
    Location:
    Harlem
    Love that video.
     

Share This Page