Ideas for connecting multiple wires to a U-lug terminal on a Dynaco amp

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  • Knottscott
    Veteran Member
    • Dec 2004
    • 3815
    • Rochester, NY.
    • 2008 Shop Fox W1677

    Ideas for connecting multiple wires to a U-lug terminal on a Dynaco amp

    Hi gang - You've guys have always proven to have a diverse knowledge base, so I thought I'd pick your brains on this one.

    I have two vintage Dynaco 70 tube amps running in mono that are connected to a pair of custom tri-wired speakers. The speaker connection terminals are the old stock screw type plates that are basically intended for a single u-lug type connector, so there's not much room for the tri-wire configuration of the speaker wire....I basically just twist them all together as best I can and put a u-lug connector in the terminal. One of them has come undone, and I'm thinking it's high time I did a better job with the wire terminations, so I'm open to ideas for cramming 3 wires into a single u-lug type termincal. TIA for any ideas!

    Here's what my terminals look like...I only use the common and the 8 ohm leads (one side per amp):
    Happiness is sort of like wetting your pants....everyone can see it, but only you can feel the warmth.
  • JR
    The Full Monte
    • Feb 2004
    • 5633
    • Eugene, OR
    • BT3000

    #2
    You could probably use a couple of this kind of spade lug connector to piggy back the wires.

    Having said that, I would think that a single pair of wires to the speakers, with tank circuits to separate the frequencies would be better setup.

    Finally, I'm envious of the amps! There is nothing like the sound of a beefy tube amp.
    JR

    Comment

    • jdon
      Established Member
      • Feb 2010
      • 401
      • Snoqualmie, Wash.
      • BT3100

      #3
      Not elegant, but you could connect two quick splice connectors (such as: http://www.harborfreight.com/50-pack...ces-96230.html) to the third wire, which is terminated by the U lug

      Comment

      • leehljp
        Just me
        • Dec 2002
        • 8429
        • Tunica, MS
        • BT3000/3100

        #4
        I would twist the three wires together and add a 4th single wire and solder, then puts some heat shrinking tubing on it. That would bring the wires of 3 down to 1. It could be made to look fairly nice, and it would be strong. You could, on the other hand, make a couple of 3 to 1 connectors so that you could undo the speakers individually in the future.

        I was thinking about the old Dynaco amps a few weeks ago, just wishing we had something like that availble today.
        Hank Lee

        Experience is what you get when you don't get what you wanted!

        Comment

        • thiggy
          Established Member
          • Sep 2003
          • 229
          • Alabama.
          • Craftsman Contractor

          #5
          I concur with Hank's suggestion. That is how it is done in breaker panels when you need to run more than one cable to a breaker which is not designed for piggy-back connections.
          SOW YOUR WILD OATS ON SATURDAY NIGHT - - - THEN ON SUNDAY PRAY FOR CROP FAILURE!

          Comment

          • LCHIEN
            Internet Fact Checker
            • Dec 2002
            • 20913
            • Katy, TX, USA.
            • BT3000 vintage 1999

            #6
            First of all we call them spade lugs, not U-lugs,

            Multiple application questions from this electrical engineer and stereo enthusiast:

            1. what wire gauges are you using to connect to your speakers (and what length?)
            2. Do you have the correct crimping tools? (not the cheapo ones they sell in the hardware stores - especially if yours came loose they not the good ones) but the full cycle ones with the ratchet to ensure they crimp all the way down.

            Presuming you had three #16 gauge wires going to your tri-wired speakers. Plans A, B and C in order of preference:

            Plan A: Normally you would use a blue insulated terminal for 14-16 ga. I would get a yellow insulated spade lug which is for 10-12 ga but will hold the equivalent wire cross section as 3 16 ga. stranded wires.
            Then I would use a full cycle crimping tool with the lug inserted on the yellow die to crimp all three wires together, making sure that they were all fully stripped and the ends matched and fully overlapped. Give it a strong pull with some pliers on each wire to make sure none of the wires will pull out on a substantial pull - a good electrical connection is also a good mechanical connection.
            The lug should have a spade for a number 6 screw.. Better than spade lugs are ring lugs which won't fall off... but you have to make sure that the screws are removable - some aren't to keep from getting lost.

            For me plan B would be to solder three wires to a fourth 16 ga. short pigtail and then put the short pigtail into a Blue-insulated #6 spade lug and properly crimp using the blue die in the crimping tool. It's not easy to solder a large bundle of wires like that together. That's basically Hank Lee's suggestion.

            Plan C would be to put the low freq wire to a blue-insulated spade lug with good crimpers. Then use two #16 T-splice insulation displacement connectors to join the mid and high frequency to the first wire within a few inches of the spade lug. That's basically JDons suggestion.

            But your plans will depend upon the questions I posed above, and probably on the availability of the correct sized spade lugs.
            Last edited by LCHIEN; 01-12-2014, 06:51 PM.
            Loring in Katy, TX USA
            If your only tool is a hammer, you tend to treat all problems as if they were nails.
            BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

            Comment

            • Knottscott
              Veteran Member
              • Dec 2004
              • 3815
              • Rochester, NY.
              • 2008 Shop Fox W1677

              #7
              Thanks much for the suggestions guys. They all have merit, so I'll mull them over and do something soon.

              I've owned a Hafler DH-500 (255wpc), NY Audio Labs Moscode 300 (150wpc), and Discrete Technology LS-2 (100wpc) prior to these, along with some receivers and integrated amps. The little Dyna 70's are by far my favorites. One of them was built by a favorite uncle in 1964, who gave it to me close to 30 years ago....it became a real treasure after he passed away two years ago. The other Dyna was picked up used for $50 close to 20 years ago. Both Dyna's were originally 35 wpc stereo, but both have been modified from pentode to triode mode, I've upgraded the caps and tubes, and both only use one channel per amp now...we estimate that they're now closer to 17 wpc. They hum, click, and pop for 30-60 seconds after they're turned on, and I know they consume a lot of electricity, but they're more dynamic than any other amps I've owned, and the sound is lusciously sweet....they also glow in the dark.
              Happiness is sort of like wetting your pants....everyone can see it, but only you can feel the warmth.

              Comment

              • LCHIEN
                Internet Fact Checker
                • Dec 2002
                • 20913
                • Katy, TX, USA.
                • BT3000 vintage 1999

                #8
                Originally posted by Knottscott
                ....they also glow in the dark.
                So do potatoes from Fukushima.
                Loring in Katy, TX USA
                If your only tool is a hammer, you tend to treat all problems as if they were nails.
                BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

                Comment

                • All Thumbs
                  Established Member
                  • Oct 2009
                  • 322
                  • Penn Hills, PA
                  • BT3K/Saw-Stop

                  #9
                  Seeing as it is all P2P wiring underneath, and seeing as you've already made some mods, I'd rewire the terminal blocks so all three connectors are wired to the 8-Ohm tap, then I'd put one connector on each terminal.

                  Comment

                  • LCHIEN
                    Internet Fact Checker
                    • Dec 2002
                    • 20913
                    • Katy, TX, USA.
                    • BT3000 vintage 1999

                    #10
                    Originally posted by All Thumbs
                    Seeing as it is all P2P wiring underneath, and seeing as you've already made some mods, I'd rewire the terminal blocks so all three connectors are wired to the 8-Ohm tap, then I'd put one connector on each terminal.
                    that's not a bad idea if you don't mind modifying the amp... that would be a little sacriligeous from a resale POV but if you don't intend to sell them then why not modify to taste.

                    Still better get a good crimper.
                    Loring in Katy, TX USA
                    If your only tool is a hammer, you tend to treat all problems as if they were nails.
                    BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

                    Comment

                    • All Thumbs
                      Established Member
                      • Oct 2009
                      • 322
                      • Penn Hills, PA
                      • BT3K/Saw-Stop

                      #11
                      Originally posted by LCHIEN
                      that's not a bad idea if you don't mind modifying the amp... that would be a little sacriligeous from a resale POV but if you don't intend to sell them then why not modify to taste.

                      Still better get a good crimper.
                      You can always modify it back if you sell/repurpose it.

                      Comment

                      • leehljp
                        Just me
                        • Dec 2002
                        • 8429
                        • Tunica, MS
                        • BT3000/3100

                        #12
                        Originally posted by LCHIEN
                        So do potatoes from Fukushima.
                        I'll take your word for it! I certainly am not going there to see them!
                        Hank Lee

                        Experience is what you get when you don't get what you wanted!

                        Comment

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