Problem with Logitech z313

[Jake_svk]

Hey guys, having trouble with my 2.1 speakers and I was wondering you could help me. Basically my speakers works fine on low volume,but when I turn the volume up ( doesn't have to be all the way) , it starts to make stuttering noise. For better understanding of the problem I opened up speakers hooked up my scope to input and output of the operational amplifier sta540. Yellow channel is an input, blue channel output. Do you have any suggestions if that amplifier is bad or is it something else. Thank you for your advice. I posted a video of the problem down below

https://youtu.be/sJZ2CDwczx0

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[cvanc]

Here's a datasheet for your amp chip, it should help https://www.sparkfun.com/datasheets/Components/General/STA540.pdf

Is your system 2 satellite speakers & one subwoofer, all powered by a single STA540?  If so, take a look at Figure 6 "Stereo Plus Bridge Drive" for a typical 3 channel configuration, where the woofer uses 2 amp channels to get more power than the satellites.  Your circuit may be very similar to this.

Could be going into protection (a load or heat problem), could be "motorboating" due to failing capacitors on the power lines, could be your power supply is collapsing when it sees a heavier load, could be lots of things.  But the datasheet is a start.  Good luck with your fix.

[Jake_svk]

Yes it is two sattelite speakers and subwofer. I though so too, it is the power supply fault so I replaced it with even more powerful. It didn't help. There are two pre amplifiers which can cause problems as well so I probably start to replaced them one by on. Thanks for the advice with that datasheet. I Will check it out

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