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McIntosh Technology

Discussion in 'McIntosh Audio' started by Negotiableterms, Dec 2, 2010.

  1. Negotiableterms

    Negotiableterms Administrator Staff Member Admin Subscriber

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    This thread will contain posts and links related to technology used in Mc gear. For example, technical explanations of autoformers, unity coupling, etc.

    It's not a place for debate on the technology, rather, it's a reference area, so please keep all posts on point.

    Thanks!
     

     

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  2. c_dk

    c_dk Addicted Member

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    Sidney Corderman Autoformer white paper

    Sid Corderman's white paper on autoformers attached
     

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  3. jchouston

    jchouston Well-Known Member

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    Oh, awesome! Great idea. For someone like me (a non-technical noob), this will be a gerat help! Thanks.
     
  4. MX117.MC7150

    MX117.MC7150 Listener Subscriber

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    Yes..... thanks for posting. Now that I've read, do recall reading before at some point in the distant past.
     
  5. c_dk

    c_dk Addicted Member

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    Turntable stuff in a McIntosh forum????

    Those of you who might have attended a Gordon Gow seminar probably remember his emphasis on turntable setup and calibration. McIntosh imported customised Wild microscopes for their dealers which some cartridge makers copied. I pulled my Wild out of storage today to see if it will help me with LSI solder job tomorrow and while cleaning it up I thought I would see if I could get some pictures thru it to my little Canon without a lens mount. I hope I can detail this out for a future post archiving what Dirk Roos (McIntosh Vice-president for Dealer Relations) taught me about measuring stylus wear back in 1979.

    I tried to include a mailer that we sent out in 1980 but it would not allow me because I already posted it under Shure stylus microscope over in the TT forum. Many of you might have received a similar mailer from your dealer back in the day.

    I am curious how well the two styli pics come out. Please let me know how well they come out on your monitors. The second, the darkest, is the most important as it shows the actual contact surfaces with minimal scatter from internal reflections and would be at the light level used to measure at the + or - 25 degree marks.
     
    Last edited: Nov 3, 2012
  6. c_dk

    c_dk Addicted Member

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    McIntosh Speaker Wite paper Pages 1-5

    Find posted the first 5 pages of white paper on McIntosh speakers from about 1982.
     

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  7. c_dk

    c_dk Addicted Member

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    McIntosh speaker white paper pages 6-10.
     

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  8. c_dk

    c_dk Addicted Member

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    McIntosh speaker white paper 11-13
     

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  9. c_dk

    c_dk Addicted Member

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    McIntosh speaker white paper The last page- speaker pictures.

    Also the second download is the speaker charting paper. Somewhere I have notebooks with hundreds of these from years of testing speakers in customers homes.
     

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  10. 427SS65

    427SS65 New Member

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    I've still got ours. It really sold a lot of cartridges and stylii!
     
  11. c_dk

    c_dk Addicted Member

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    MQ107 and customer preference

    I have attached pages 2 and 3 of the MQ107 owners manual highlighting McIntosh's position in th 80s on room voicing and the feedback we as dealers reported back to them from our customers.
     
    Last edited: Dec 6, 2012

     

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  12. sKiZo

    sKiZo Hates received: 8642 Subscriber

    Here's page 4 from the MQ104 manual ... same thing, only different?

    [​IMG]
     
  13. Rich Andrews

    Rich Andrews Well-Known Member

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    Dr. Floyld Toole wrote a series of white papers on loudspeakers that are actually quite good. The one article that really struck home is one titled "Maximizing Loudspeaker Performance In Rooms" It was his description of a Karlson cabinet that really made sense. My father build two of the Karlsons for 15" woofers. After he died I dismantled and tossed those cabinets into a dumpster which is where they should have been in the first place.

    I actually did some of my own measurements and calculations long before I had heard of Dr. Toole. These measurements were to determine what sort of driver would actually work well in a Karlson. The resultant data described a driver that could not exist. It was akin to making a box that was bigger on the inside than it was on the outside.

    Look up the Floyd Tool white papers. They are a good read. In all respects they agree with the McIntosh white papers.
     
    Last edited: Nov 10, 2012
  14. o0OBillO0o

    o0OBillO0o Active Member

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  15. o0OBillO0o

    o0OBillO0o Active Member

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  16. Pio1980

    Pio1980 AK Member Subscriber

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  17. damacman

    damacman Blown and Injected Subscriber

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    Wow . . . I had no idea that Stephen Mantz restored those amplifiers (they've been on eBay for a bit now). In my old circles, Stephen was known as one of the car amplifier gods.
     
  18. Mr. Orange

    Mr. Orange Flat speakers rule!

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    :thmbsp: What a great thread. :thmbsp: Thanks for starting this! :yes: :D
     
  19. Mike Gibson

    Mike Gibson Modulator Staff Member Super Mod Subscriber

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    This post was written by Dave Gillespie and not I. Also it was brought to my attention by member Pio1980. It is a very concise explanation of how the Unity Coupled Stage works.

    This question was asked on another AK forum, specifically as it relates to biasing, and the screen grid connection. I was asked to repost the answer I gave there on this forum, for the benefit of those here who are interested in the McIntosh design. That post follows:

    "The Unity Coupled circuit is a tertiary feedback arrangement. But to be more specific, it is exactly a 50-50 arrangement. That is, whereas in a conventional arrangement, the load for either tube is presented entirely at the plate, in this case, 50% of it is at the plate connection, while 50% is at the cathode connection. These two sections together then make up the total impedance that would normally be seen at just the plate in a conventional arrangement.

    Since the peak AC voltage seen at the plate under full power conditions would normally be about 350 volts in a conventional arrangement (assuming the same tubes and operating/loading conditions), that means that 175 peak volts is appearing at the cathode with the 50/50 split arrangement that the Unity Coupled design uses -- which produces some serious challenges for the driver stage, requiring the boot strapped cathode followers etc., that appear before the output stage.

    But this 175 peak volts that appears at the cathode would also cause serious reductions in power output if the screen voltage were held constant. If this were done, the application of increasing power output causes the cathode voltage to increase on the tube that is being excited, which against an otherwise steady screen voltage, would produce a net reduction in screen/cathode voltage as power increased. With an effective ever increasing reduction in screen voltage with increasing power output then, maximum power output becomes significantly limited.

    What to do? Attach the screen to the opposite tube's plate! Why? We know that when one tube is conducting, its cathode voltage is rising, and therefore, its plate voltage is falling. But the exact opposite is happening in the opposite tube. It's plate voltage is INCREASING (while its cathode voltage is falling). Since the cathode voltage is rising in the tube that is conducting, and with the screen of this tube connected to a source that is also rising by the same exact amount (it must since the windings are all 50/50, remember?), then it means that now, the effective screen voltage in each tube does not change, in spite of increasing power output. Quite a neat, but very necessary little trick.

    As for the bias, because there is so much feedback employed in the output stage (100% if you base it on just the signal developed at the plate), then a critical setting of bias became unnecessary for Mac to achieve its stated performance specifications. They could even relax quiescent current draw, and still meet the specs because of it. With such relaxed current levels, virtually any tube could be installed without any real concern for excessive quiescent dissipation levels, since such a relaxed setting would accommodate virtually all tubes in this setting. No doubt, the bias could be tweaked for even better performance, but to achieve the published specs, it wasn't necessary.

    The whole affair requires very tight coupling in the OPT between the various windings, which in part, generated the "Unity Coupled" name given to it because the windings are so closely coupled. Special bifilar and trifilar winding techniques were used to attain such tight coupling, with the results being more expensive to produce, but producing performance which speaks for itself.

    I hope this helps!

    Dave"
     
    Last edited: Feb 26, 2014
  20. chuckworkb

    chuckworkb AK Subscriber Subscriber

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    Thanks for these postings. Look forward to more.
     

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