Electronics > Beginners
how to isloate audio ground from the amplifier
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Adhith:

--- Quote from: Buriedcode on March 23, 2018, 06:00:37 pm ---SO yes, the area you indicated is "ground" (0V reference).  I have also attempted (badly) to show the signals on the speaker outputs.  Neither of them goes negative, but the signals are centered on half the supply voltage, and are opposites - the speakers on care about the difference between these signals.  Connecting your VU meter to one of these terminals, and our actual ground (as indicated on the diagram) would mean your VU meter would show half voltage at all times.  Using a DC blocking capacitor would mean it only see's AC, but as each output is only half the signal it would show half the voltage.

Try it yourself - connect your VU meters ground to the amplifier boards ground, and the "signal" to one of the speaker outputs - any of the 4 outputs will do.  And see what it shows.

--- End quote ---
I just used a multi meter ohm function and found that the dc jack ground and the left channel ground is having a resistance of 350 ohm.
Adhith:
Ill connect  the ground to the vu meter let you guys know about it.
Buriedcode:

--- Quote from: Adhith on March 23, 2018, 07:17:59 pm ---I just used a multi meter ohm function and found that the dc jack ground and the left channel ground is having a resistance of 350 ohm.

--- End quote ---

The left channel has no ground. Nor does the right channel.  No speaker is connected to ground.  Both terminals of the speaker are driven by push-pull outputs. In this way the reason they label them "+" and "-" is for phasing.  If you connect speakers backwards you will still hear music it will just be out of phase with the other channel, it has nothing to do with ground reference.
Zero999:

--- Quote from: Adhith on March 23, 2018, 07:20:10 pm ---Ill connect  the ground to the vu meter let you guys know about it.

--- End quote ---
Yes, that will work.

As this is a class D amplifier, you might find the existing filter is inadequate at removing all the high frequency content, so the VU meter might indicate there's a signal, even though there isn't one. Another RC low pass filter might be required, before the VU meter.
Audioguru:

--- Quote from: Hero999 on March 24, 2018, 04:44:48 pm ---As this is a class D amplifier, you might find the existing filter is inadequate at removing all the high frequency content, so the VU meter might indicate there's a signal, even though there isn't one. Another RC low pass filter might be required, before the VU meter.
--- End quote ---
Good point. We cannot hear ultrasonic switching of the class-D but the VU meter might show it.
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