Muffled Sound, Underwater like Sound TDA2030

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#3
chanish said:
I am having problem with one of the stereo channel. It sounded muffled and the vocals is barely audible.
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Use basic troubleshooting. Swap channels starting at the input, and continue swapping
at each point possible, including each end of connecting cables, going toward the speakers.
The first time the problem switches channels, the problem is the component just before that point.

If you finally swap the speaker wire ends behind the speakers, and the problem doesn't switch,
then interchange the speakers. If the problem still is in the same side, then it's acoustical.
 
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#4
@ Mark Whitney: Thank you for your reply. At first I thought its the player because I was using my phone to play the music and then I bought an mp3 player and still the same thing. In my video I mentioned that I was previously using 10k pot and cleaned it with WD40, but still the same problem and led me to replace with 50k pot but nothing change. Though I will try to use a different cable.

@ Rayma: Thank you for your reply. As you've seen in my video, I was playing the music in stereo setup, then I removed the input in the channel that is working good so to highlight the problem of the other channel. I even switch the input of the bad sounding channel to the input of good sounding channel and it is working perfectly and vice versa. Its not shown in my video, but I have tried switching inputs and speakers but the problem stays in 1 specific channel. I even desoldered the chips and switch them but the problem remains the same.
 
#5
Sounds like the "muffled" channel is playing the difference signal between the L and R input. Check if the input source signal and ground got swapped with amp input and amp ground. in other words:
source ground --> amp input1
source channel 1 --> amp ground
source channel 2 --> amp input 2
This will cause one good channel and one sounding off (channel 2 in this example).
 
#6
At 5 minutes you "shift the connection to the other channel". Now we are listening to the same left amp from the right source input. The conclusion must be that the problem is before the amps.
Can you post a photo of the underside of the pot board and confirm that the ground of the cable is connected to the correct pot terminals. Try connecting the player directly to the amps without the pot or use a different cable. Test the player playback through headphones just to confirm that it is not the player.
 
#7
@ Mark Whitney & Johnr66: You are both correct. The main culprit of the problem is the cable I'm using for the input signal. It's a cut-up from an old unused 3.5mm jack. The thing is, I got an impression that the black wire is always connected to ground so I didn't bother my self checking the connectivity of the cable to the jack so I considered the red and white cable as the + input signal. In my case, it must have been the manufacturer's mistake to connect the red wire to the sleeve of the jack (ground) and the black wire to the ring, so I kept connecting the black wire to the ground which is supposed to be for the right channel input. From now on, I'll make it a habit of checking the connection of each cable for connecting to the amp. Because of that, one of my woofer got burned when I'm testing the subwoofer part which produced a very loud whistle. But now everything is ok, the subwoofer part is working fine though the main volume should be at least at the middle or past the middle turn before the bass kicks in. Is there a fix for that? Note that I am only using a woofer with frequenzy range of 120hz to 18khz for testing purpose only until I got my hand on a subwoofer. Anyway, it's a very lengthy reply, thanks for the effort of helping me.
 
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