68 Custom RI Twin Reverb ext. Speaker ??

Discussion in 'Amp Tech Center' started by clayton58, Apr 5, 2020.

  1. clayton58

    clayton58 TDPRI Member

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    So. If I unplug my internal speakers and and plug them into the extension speaker jack.... does that cause like fire or damage?
    Honestly, I did it ONLY momentarily.
    The reason was to see it that would help the white noise. It did, but with volume loss. So I put it back like the people who designed would want.

    ALL THAT just to ask.... I have a 4 ohm Fender Rumble cab. How would or could you hook the Twin into it, without fire or personal injury? :) Only to test noise level. Thanks. o_O
     
    Last edited: Apr 5, 2020
  2. Dacious

    Dacious Poster Extraordinaire

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    DO NOT run it with nothing plugged into the main speaker jack. In Fenders (not all other brands) that is a shorting jack. With nothing in it, there is a dead short across the poles. If you run 0 ohms in parallel with speakers you will get effectively zero ohms and damage your output transformer.

    It's unlikely run for a short time like this it would cause damage.

    The extension speaker jack is to add speakers in parallel. The main shorting jack is so you don't damage the transformer if you forget to plug something in and turn it on. That's marginally worse.

    To run the 4ohm rumble cabinet, just plug it in to the extension jack. Your internal speakers are 8+8/2=4 ohms.

    The 'white noise' in the 68 series amps is the result of reduced negative feedback plus a more aggressive Bassman type tone stack.
     
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  3. Lowerleftcoast

    Lowerleftcoast Tele-Holic

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    You have two speaker jacks on the 68CTR. Speaker and ext speaker. You would unplug the internal speakers from the "speaker" jack and plug the 4ohm cab into that same "speaker" jack.
     
  4. clayton58

    clayton58 TDPRI Member

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    Thank you!
     
  5. Dacious

    Dacious Poster Extraordinaire

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    Big Fenders like yours (Deluxe Reverb and up) will tolerate a 100% mismatch to the rated ohms - you can go 2ohm total load (adding your Rumble cabinet in the EXTN jack) to the internal speakers. That's 4X4/4+4=2 ohms.

    Or you can plug an 8 ohm load in the Main jack.

    You may find the Rumble speaker puts out little apparent volume - if it's less efficient than the Celestions in the Twin, you'll get not much out on any given amplifier volume setting.
     
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  6. clayton58

    clayton58 TDPRI Member

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    Thank you!
     
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