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| how to isloate audio ground from the amplifier |
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| Adhith:
hello friends, I'm working with a speaker project which also has a vu meter along with it. For the VU meter the audio input is fed from the amplifer output (from the left channel positive and ground). but while connecting the ground wire from amplifier output to the VU meter input, the speaker produces a distortion sound and I believe its because of lack of isolation between the audio signal from the amp and the VU meter circuit. So what should I do to isolate the ground?? I have already completed the project so im looking for smaller solutions to fit inside the enclosure. does a diode at the audio ground solve the problem or should I use an audio transformer??but I don't know how to use it. Could anyone help me out??. Thank you in advance. |
| Audioguru:
The output of your amplifier might be bridged. A bridged amplifier output has two amplifiers. Each amplifier feeds one speaker wire but the signals are with opposite phase so that the output voltage across the speaker is doubled which produces almost 4 times the output power. Then your connection of the VU meter ground is shorting one output of the amplifiers to ground. Connect the input ground wire of the VU meter to the amplifier's ground instead then it will show half the speaker's voltage. |
| Adhith:
Thank you very much for your reply. I'm using a 25W+25W amplifier module for my project which is based on the class D chip TDA7492P. I have attached a pic of the board below. Could you explain a bit about where to find the amplifier ground?? |
| Zero999:
The amplifier is definitely bridged. The schematic is probably similar to the one found on the data sheet and the ground connecting can be found, using the continuity test function on a multi-meter. http://www.st.com/content/ccc/resource/technical/document/datasheet/35/01/97/6b/20/ce/40/6f/CD00211320.pdf/files/CD00211320.pdf/jcr:content/translations/en.CD00211320.pdf |
| Audioguru:
Are you the guy who is feeding only one channel of the Bluetooth stereo to only one speaker? The TDA7492 in your photo is missing the heatsink shown on the product from AliExpress. |
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