Quick question about the Speaker jacks on a Princeton (6G2)

Discussion in 'Shock Brother's DIY Amps' started by RatBug, Sep 20, 2019.

  1. RatBug

    RatBug Tele-Meister

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    Looking at the Fender Layout
    https://cdn.shopify.com/s/files/1/2325/2729/files/Princeton-6G2-Layout.pdf?5926397210715640943

    and examples I have found online the Speaker out and Aux speaker out are two differrent kinds of plugs. One is a Switchcraft 12A style and the other is a Switchcraft 11 style.

    It's my understanding that the 12A style has a grounding shunt that is deactivated when a 1/4 plug is inserted and that is there to pull the tip to ground when nothing is plugged in to that jack and help with noise on the empty jack.

    If that is the case then why is it that in the Fender layout diagram and most of the examples I have found have the Shunted jack (12A) on the Speaker plug and the bare shuntless version (11) on the Aux speaker plug? This leaves the mostly empty (unless and external cab is being used) plug shuntless and open to noise.

    It seems it should be the other way around, or even better a 12A shunted jack on both.

    Am I missing something?
     
  2. peteb

    peteb Friend of Leo's

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    I'd say its this:





    my understanding is that it is not to help with noise but to protect the output transformer if no speaker is plugged into the main speaker jack. The OT would rather see a short circuit than an open circuit. A tube amp is not supposed to be run without a speaker plugged into the main speaker jack.
     
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  3. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    @peteb is correct - it's to help save the OT. You don't want to shunt the secondary unused one, as that will ground out your signal.
     
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  4. Paul G.

    Paul G. Friend of Leo's

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    If you have 2 shorting jacks then when you're plugged into one, the other still sends the signal to ground. The power will flow through the path with the least resistance, so you will get little or no output and eventually will fry your output transformer.

    And yes, the shorting jack is there to provide short-term protection in case you forget to plug your speaker in. Key is short-term.
     
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  5. RatBug

    RatBug Tele-Meister

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    Thank you all very much for the help and info.
     
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