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| auto noise rejection |
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| timelessbeing:
I bought a wun hung lo USB panel for my car. It's got a little built-in SMPS. It charges devices just fine, but when I use it to power my music player, you can hear noise in the audio output. The nosie varies with engine RPM, so I'm guessing that ripple from the alternator is getting through. Is there a way to eliminate it? Would adding caps to input help? Has anybody purchased a similar device which is better quality, and has known clean output? |
| tautech:
--- Quote from: timelessbeing on March 05, 2018, 11:59:18 pm ---I bought a wun hung lo USB panel for my car. It's got a little built-in SMPS. It charges devices just fine, but when I use it to power my music player, you can hear noise in the audio output. The nosie varies with engine RPM, so I'm guessing that ripple from the alternator is getting through. Is there a way to eliminate it? Would adding caps to input help? Has anybody purchased a similar device which is better quality, and has known clean output? --- End quote --- Don't guess, measure it to verify its source ! |
| ammjy:
by the experience, we can use 1 0.1 0.01 uF .. but if it would not give help. we can analyse noise via FFT of scope. and in many case of automotive. ferrite core give lot of help. in my case. i have lot of caps. i just put with many mix. if noise gone then success !! i dont calculate sometimes.. because im lazy...... |
| timelessbeing:
I thought ferrites were for attenuating high freq noise... as in far beyond audible range? |
| tonyh88:
I agree with Tautech. What equipments do you have access to measure it? Scope? Did you check with a multimeter on AC coupling if you see anything at all? You can probably filter it but without knowing the noise frequency it will be a trial and error thing. |
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