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Got a 65 Super reverb today... BUT I NEED HELP!

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  • #46
    Originally posted by Fee View Post
    that's the good thing about it - you can safely go from two ohms to four
    the original Fender output trannies were built very tough and could handle mismatches. Unlike the Marshalls .........
    The transformer doesn't really care what you do. You could run it at 400 ohms and the transformer would sit there as it has since 1965. The output tubes, however, are going to have a different opinion. Tube amps work kind of the 'opposite' of transistor amps as far as output loads go. Increasing from 2 to 4 ohms is going to change the load that the output tubes see. Is it going to fry them up right away? No, probably not. You are safer to go LOWER, but it's generally accepted that higher isn't good. Tubes prefer lower impedance loads to high impedance loads. Take a look at the output jacks on any old Fender amp head. You'll have the 'Speaker' and 'Extension' jacks. (or whatever they're called, I don't feel like getting up and looking). The speaker jack is set up to actually SHORT out if there is no load connected. The output tubes are happier with a short circuit than they are with no load. And the extension speaker jack is just wired in parallel. This is so that if you connect an additional speaker, the impedance the tubes see is going to drop, not increase. This is all designed into the amp. It would be best to run the amp at the correct 2 ohms.

    I can run my car down the highway at 60MPH in 3rd gear, or I can run it at 60MPH in 5th gear. The outcome is basically the same. You can get from A to B in the same amount of time. The former way is going to generate more heat and wear things out faster. The vehicle was designed to cruise happily at 60 with the transmission in overdrive, running cool, quiet, efficiently, and overall lasting longer.

    If you want to run your 2 ohm amps at 4 ohms, go ahead, it's not likely to let the smoke out, but be aware that the output tubes would be happier with the correct load. They will last longer, but perhaps most importantly SOUND better.

    For using multiple speaker arrangements, a transformer with multiple output taps would be ideal. In the name of keeping a vintage amp vintage, speakers wired to provide a 2 ohm load would be the best solution.

    Right on one count though, the Marshall transformers were definitely (and still are, really) weaker than Fenders. Fenders are overbuilt tanks.
    Last edited by akimball442; 08-04-2011, 01:34 AM.

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    • #47
      sorry but you'd best check again

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