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Is my SA25 plate amp broken?

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  • Is my SA25 plate amp broken?

    This might be a silly newb question

    A few months back, I bought an SA25 plate amp to use in a Voxel sub.
    For about a month and half it was pretty great, and I could feel a noticeable effect when I twirled the gain knob.

    However, the last week, I don't sense any difference or any output?
    The light still turns on, but I don't sense any change when I change the gain knob.

    Did it just blow up? I'm new at this. :p

  • #2
    Check to see if both RCA plugs are connected properly. Loosing one side will cut output significantly.
    *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 *Cello's Speaker Project Page

    *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF


    • #3
      If the rca connections are good you can pull out the driver and make sure a connection didnít come off there. You can also test the driver with an ohm meter to make sure it is not an open circuit (should be likely around 3 ohms for a four ohm woofer).

      If that is all good inspect the amp board with your eyes and nose for anything burnt. You could also hook up a different loose woofer to see if the amp has output and it is a driver issue.

      Breezy Monitors:
      Vintage Style 2-way:


      • #4
        Thanks for the tips.

        I'm not sure about RCA, since I'm using wires directly onto the plate amp spring terminals.
        I'd assume that no signal would come out from the speakers if the connections were bad?

        As for the woofer, I took it out and everything is on tight!
        I'd carefully crimped the terminals and placed a blob of solder to secure things previously.

        I'll try taking out the amp board.

        Note sure what to do if this doesn't fix it....get a new amp board? RMA the thing? Contact Parts Express?


        • #5
          Before taking it apart, contact Parts Express. They have good tech support and warranty.


          • #6
            Thanks! I'll email them


            • #7
              What are you using as a source? If something changed on the source side (high pass filter, speakers set to "small" instead of "large" etc) would cause virtually no bass response from a subwoofer amplifier using high level inputs.
              Your results may vary.


              • #8
                Plate amp was broken. I took it apart, and wiggled some of the internal ribbon connectors--it would work with some jiggling and held in tension a certain way.--it was a solder joint.

                The Plate amp is the source--I ran the SMSL AD18 through the plate amp to the speaker. The SMSL just sends a straight signal, which the plate amp will help set the cutoff for the subwoofer.

                Parts Express was quite good about accepting it back. I'm looking forward to the replacement. Paul's voxel sub sounded damn good.