Can someone tell me how I've hooked up this low-pass filter wrong?

leo135
leo135 used Ask the Experts™
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I have a PC sending audio to an amp via a 3.5mm/phono cable. The amp then amps the audio and sends it to a subwoofer via normal speaker cable - and +

Works great.

I wanted to introduce a low pass filter after the amp, before the SW, and I've hooked it up as in the image below. Even though the filter is getting power (LED works), the SW isn't getting any audio.

low-pass.png
I have a feeling I am doing this completely wrong, and was wondering if anyone had any advice to get it working? Happy to buy more cables but if I need to by more equipment, unless it is under £5 I will just abandon the project.

Thanks for any and all advice
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Principal Software Engineer
Commented:
I wanted to introduce a low pass filter after the amp

1.  This low pass filter is intended to work at line levels (millivolts), not speaker levels (volts).  The input is being way overdriven and the output is insufficient to drive speakers.

2.  As the intended input levels are millivolts, feeding thousands of times that into the filter may have burned out the input stages.

Possible fix:  Connect the filter's input side to the PC's audio output.  Connect the filter's output side to the amplifier's input.  Then see if it is still operational.

As a side note, this filter does exactly the same thing as the BASS level control on the amplifier.

Author

Commented:
Thanks. I will try. I have to figure out how to get a 3.5mm jack cut and attached to the input/output but I am sure I can google that.

As to your sidenote: so this device won't filter out the higher frequencies? It just modifies the lower frequencies?

Author

Commented:
Thanks, perfect.

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