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  • confusing extra speaker jack

    Who uses an extra 8 ohm speaker as shown on the original schematic on a 5E3 with an 8 ohm output transformer? I have a MercMag FTDO-59 that I awaiting an answer on this question also.
    It's weird, because it WAS working fine.....

  • #2
    What is your concern/confusion? That you will have a 4 ohm load on an 8ohm OT secondary? That was how Fender did it on most of their amps for decades. Their output transformers were very robust and they were not concerned with impedance mismatching. They just added an extra jack in parallel with the speaker jack so you could add another speaker. When you used the ext.spkr. jack you would always end up with an impedance mismatch.
    Originally posted by Enzo
    I have a sign in my shop that says, "Never think up reasons not to check something."


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    • #3
      Originally posted by g-one View Post
      What is your concern/confusion? That you will have a 4 ohm load on an 8ohm OT secondary?
      yes that's it basically. Mercury Mag recommends not using the extra speaker, but say that Fender did it forever. But I think their concern is more about tube life.
      It's weird, because it WAS working fine.....

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      • #4
        Oh that isn't an issue either really.

        All the impedance mismatch does is push the signal down the tube curve. This isn't like trying to run a solid state amp into a 1 ohm load or something. Mercury wants to sell you a transformer.
        Education is what you're left with after you have forgotten what you have learned.

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        • #5
          They may be concerned about tube life. But they don't sell tubes, they sell transformers. So what they should be concerned with is selling you their more expensive transformer with multiple impedance taps.
          Originally posted by Enzo
          I have a sign in my shop that says, "Never think up reasons not to check something."


          Comment


          • #6
            No, just buy more speakers! Why not just plug it into two 16ohm cabs? 5E3 stack, anyone? And no mismatch. My Concert sounds incredible through 2x15 + 2x12... probably overkill, but fun! I don't recall who here told me I could do that - use two speakers or cabs that are double the nominal impedance, one speaker/cab per jack.

            But I've been mismatching my Bassmans for a few years. As stated above, I wouldn't worry too much about it.

            Justin
            "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
            "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
            "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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            • #7
              Well, I bought 2 sets before I ever asked this question. Mercury cites tube life and the possibility of one shorting and taking out the OT.
              It's weird, because it WAS working fine.....

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