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NAD (vintage tube amp content)

Discussion in 'Amps and Cabs [BG]' started by cfsporn, May 9, 2015.


  1. cfsporn

    cfsporn

    Aug 20, 2011
    New York City
    I have a lot of questions about my first tube amp, but let's get the important stuff out of the way first.

    Pics!
    Please excuse the dust.

    image. image. image. image. image. image. image. image. image.
     

    Attached Files:

    dukeisdog and Tbone76 like this.
  2. CatSquare

    CatSquare

    Mar 7, 2014
    12ohms?! Is that a vintage tube amp thing? I've never heard of that​
     
  3. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    Well the older standard was a nominal impedance of 3 ohms, 7.5 ohms and 15 ohms.
    So that's to work with 4 x 3 ohm drivers in series.:)
     
    cfsporn likes this.
  4. cfsporn

    cfsporn

    Aug 20, 2011
    New York City
    Yeah. 12 ohms. I'm not too happy about that as it means that this will need more than a recap/retube before I can use it. I think the cabs that were sold in this amp had three drivers, presumably in series so that explains the 12 ohm tap. An early way of making sure you bought their speakers if you will.

    I wonder if I could drop in another OT without extensive modifications.
     
  5. cfsporn

    cfsporn

    Aug 20, 2011
    New York City
    When was the standard changed?
     
  6. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    Early Seventies my 1971 Simms Watts is marked up as 7.5 or 15 ohms and my 1975 Roost is marked up as 4/8/16 Ohms.
     
  7. lowphatbass

    lowphatbass **** Supporting Member

    Feb 25, 2005
    west coast
    Have you checked the tranny to see if it's got other taps?
     
  8. cfsporn

    cfsporn

    Aug 20, 2011
    New York City
    Interesting. I wonder why the standard was changed? I also wonder if the standard was always 4/8/16 and Simms Watts was trying to ensure that you used their speakers with their amp.
     
  9. cfsporn

    cfsporn

    Aug 20, 2011
    New York City
    Not yet. The OT and the PT are actually on the same side of the amp (did they not know the formula for center of gravity in 1967 or something?) with the OT located behind the PT. Once I get it taken apart for a recap, I'll look for other taps.

    In the mean time, could I put in an aftermarket OT? I know Mercury Magnetics has one that is designed for 200 watt bass amps, but I'm not too familiar with the technology.
     
  10. waltdogg

    waltdogg

    May 24, 2014
    I don't think there is a "standard." Impedance changes with frequency and other factors. With a tube amp, you can always go lower than the suggested load. Just don't leave in on with no load. For example. Your new amp will handle an 8 ohm load no problem. But turn it on without a cab any say goodby to your OT.
     

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