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Easy audio signal pickup for the original KAB250 amp?

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  • Easy audio signal pickup for the original KAB250 amp?

    I have two of these amps: https://www.parts-express.com/dayton...th-40--325-104

    and was meaning to create a cool little project with them when I was part of the Design Team. Needless to say, I found it challenging to get three (well, actually 4) projects done in a year's time and I wasn't able to complete the little amp project I had planned.

    I'm feeling the bug again and would like to give something a try if possible:
    This amp has both a 3.5 input as well as built-in Bluetooth. I'm wanting to add a small spectrum analyzer to the mix on the input side. It is very tiny, just under an inch diagonally screen-wise, and it only needs one side, L or R
    +/-
    to work.

    I'm wondering if there is a fairly easy way to get a signal to the little Spectrum analyzer regardless of input....

    If it didn't have Bluetooth, I'd just tap into the 3.5 input, but then every time BT fires up, I'd have no display. Also, I thought about resistor-ing the speaker level outputs to provide signal, but then you'd only have display fill based on the volume output to the speaker which won't work either.

    Thinking about it although I know nothing about how these things work... I'd say that there must be some kind of auto-sensing function somewhere on the board that changes inputs from either BT or the 3.5mm input. I guess that's where you'd need to splice in.

    I kind of doubt that it's possible, but I'm just wondering if anyone had happened to mess with this aspect of this older amp board already and knows if it's possible or not.

    TomZ
    Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
    *Part 2 *Gluing multiple curved laminations of HDF

  • #2
    Try taking it at the volume control. It's a pretty close design to a TI or Sure reference board. The Sure reference boards show the volume control out to line level input wired together when you stack the boards together to build a 2.1 amp.

    Comment


    • #3


      On the product page there is a link to the pinout for the board, J11 has LOUT and ROUT, seems to confirm devnull's suggestion. Looks like it might be fairly easy.
      Attached Files

      Comment


      • #4
        Devnull and GTPlus,
        thanks for the input.

        Get it?

        Really, I didn't think of that for some reason, it's a great idea. I have the plug in board with the pot built in, I'll have to shorten that up no doubt, so I can probably tap part of that hook up fairly easily. It's easy enough to test with the board before altering it also.

        BTW, this is the little spectrum analyzer that I'm going to be using... YouTube video... https://www.youtube.com/watch?v=Igsil6f6ey4

        It was like $15 shipped from China.

        It uses 4 leads to run it...
        (1) for 5v power (+),
        (2) for + input signal,
        (3) for the switching, which contacts with...
        (4) the (-) lead which is also (-) for the 5v power, and
        (-)
        for the input signal.

        wonder what ground issues I'll have with this setup!
        I now know how to handle that though thanks to the guys on this board.

        Thanks for the help fellas,
        TomZ

        Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
        *Part 2 *Gluing multiple curved laminations of HDF

        Comment


        • #5
          Originally posted by Nesbitt357
          The extremely versatile Dayton Audio KAB-250 Bluetooth Amplifier Board allows for quick and easy addition of audio to any project, speaker build KrogerFeedback
          Oh good, another bot, just what we needed!

          Comment


          • #6
            Man what is it with these bots lately


            Tom,

            That spectrum analyzer is pretty cool, be interested to see it up and running running when you are done.

            Comment


            • #7
              Due to a snow storm, we had a delayed opening today at the school where I work so....

              I tapped into the volume control board on the amp and was able to get a proper signal pre-amplification to feed the tiny spectrum analyzer from.

              Click image for larger version

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              It does produce full screen visual no matter where the volume is positioned/how loud the volume is turned up. I need to clean up that solder joint a bit, but under the magnifier it's not really as close to touching as it looks in the pic. Anyway, I'll touch it up a bit anyway, just to make myself feel better.

              The main board had the lines going to the volume board clearly marked, I traced them to the little board and tapped in there. I saw several other thru-hole connections on the board, but couldn't seem to get a good signal from any of them, so I just went right to the pot connection.

              I don't think there was any added noise... I actually had one of the channels connected to the subwoofer so I could see what the little amp board could do with some bass. I hadn't hooked it up before actually. I'll have to plug it into an actual speaker with a tweeter to see for sure.

              So, it works, thanks guys for the input. Here is a little video to prove it: https://youtu.be/YR230STkWFo

              I'm planning on making a little vertical desktop amplifier out of this in the coming month or two in my 'free' time. I'm calling it the "Trapazamp" based on it's trapezoidal shape. There aren't too many vertical amps out there, the one I have planned should be kind of cool, besides the little spectrum analyzer, I have a few things in mind for this (possibly) that will make it kind of neat.

              TomZ
              Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
              *Part 2 *Gluing multiple curved laminations of HDF

              Comment


              • #8
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                • #9
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                  Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                  *Part 2 *Gluing multiple curved laminations of HDF

                  Comment


                  • #10
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                    Comment

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