Wondom Amp to Overnight Sensation MTM

Discussion in 'General Topics' started by itsmeuri, Oct 26, 2016.

  1. Hi folks,

    I'm a first time builder and I've run into a problem...

    I purchased a Wondom 2x30W Class D amplifier board and would like to use it to power my single speaker Overnight Sensations MTM kit. I was attracted by the Bluetooth capability of the board, and the fact that all the wires and connectors were included...

    But, the amp is two channel, and the speaker kit is mono. I didn't think this would be a problem, because I found this simple wiring diagram that illustrates how to merge two outputs into a single input.

    So, to test my setup, I'm using the headphone jack in my cell phone. That goes into the 3.5mm audio jack aux input into the amp board. The amp board has outputs for L+, L-, R+, and R-. I joined the L+ and R+ wires with 10K ohm resistors on each, just as pictured in the diagram. The joined positive wires go into the + input in the crossover, and the joined negative wires go into the - input in the crossover.

    After plugging in a power supply and starting some music on my cell phone, I slowly turned up the volume using the volume pot provided with the amp board. I just barely heard a hint of music before everything cut out.

    Thinking those resistors were too much, I swapped them out for 1K ohm resistors. This time the music sustained for a bit longer before cutting out.

    I did some more searching and found this diagram. It shows an added resistor of much higher resistance going from the joined positive wires to the joined negative wires. I added this feature using a 47K ohm resistor. The result was similar. The music played at a very low volume and didn't cut out until I turned up the volume further.

    So, what am I doing wrong? Am I applying the nifty wiring trick at the wrong spot along the journey? Should I be using different resistors? Does the music cutting out indicate that the board is protecting itself from something? Should I just quit wasting my time and pick up a mono amp board?

    I'm hesitant to keep experimenting for fear of damaging the equipment.

    Here's a top down shot of my setup. I don't know how useful this image is, but maybe it'll help...


    Any help would be much appreciated!
  2. Have you tried to power the speaker from only one channel of the amp? I would think that while 15W may not be enough for your long term use plans, maybe you could determine if there was some error in your crossover or something simple before you try to join the two amp channels. One problem at a time.

Share This Page