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.

 

Is the VU meter connected directly across the Left channel speaker? What type of VU meter is it? What type of amplifier?
SG

 

Is the VU meter connected directly across the Left channel speaker? What type of VU meter is it? What type of amplifier?
SG

The amplifiers drives the left and right speakers. another taping is taken from the left channel for the VU meter input. The VU meter is based on LM3915N logarithmic display IC. The amplifier is bought online. It is class D amplifier based on TDA7492P IC. I have attached a pic of the board below

 

try using a audio input isolator, it is basically a 1:1 ratio audio transformer, look where they sell car Amp parts, it'll usually have RCA connectors on it,, it goes between amp input and the audio cable from the radio.

 

Your problem is that the outputs are Bridged and don't use a Ground, so you can't connect anything with a ground reference to the speakers. You will have to use the input signal and amplify it or use an audio transformer to convert it to a single output.

 

Your problem is that the outputs are Bridged and don't use a Ground, so you can't connect anything with a ground reference to the speakers. You will have to use the input signal and amplify it or use an audio transformer to convert it to a single output.

DD is right! Thus using an isolation transformer is what is the best choice. OR use a totally isolated power supply for the VU display circuit. But an audio isolation transformer is the better choice.

 

You could use gnd for the VU meter and connect the signal input to just one speaker terminal. In a bridge amp, both sides of the speaker are driven antiphase, so only one side needs to be used for your meter.
Just ensure the VU meter is capacitivle coupled.
That does look like a class D amp so you may need to add a series filter if the onboard filters do not remove all the PWM frequency.
Another way is to feed the VU meter from the amp input.

 

 

Did you fix the VU meter errors like I said on the other forum?

 

c

Did you fix the VU meter errors like I said on the other forum?

I'm working on it sir, brought the components for it today and finish it as soon as possible .