It's measured with the meter connected directly across the speaker terminals for each individual channel.
Some amps have a significant DC offset with no speakers or load connected (the massive 1500/sinuslive amps are one example) so if you get excessive DC offset, try connecting a speaker or dummy load and re-checking.
The acceptable offset varies by manufacturer or technician. Some consider 25mv to be the upper limit. I'd say 50mv is OK. For some amps, it's not worth chasing down even higher offset. For large class D amps, I wouldn't consider 100mv to be excessive. Others would disagree.
Some amps have a significant DC offset with no speakers or load connected (the massive 1500/sinuslive amps are one example) so if you get excessive DC offset, try connecting a speaker or dummy load and re-checking.
The acceptable offset varies by manufacturer or technician. Some consider 25mv to be the upper limit. I'd say 50mv is OK. For some amps, it's not worth chasing down even higher offset. For large class D amps, I wouldn't consider 100mv to be excessive. Others would disagree.
Just to clarify when you say across the speaker terminals you mean negative probe to negative speaker terminal and positive probe to positive terminal? I managed to get this audio pipe 3k to power up and from ground to one of the negative terminals is 500mv.Seemed high is why I posted.Does that sound like an issue?
It depends. If the amp otherwise works perfectly but has a bit of offset voltage, the problem is likely in the differential amplifier (the part of the amp that compares the input to the output and corrects for errors).
If there is excessive offset and the amp doesn't function properly, there are likely defective components that will need to be replaced.
If there is excessive offset and the amp doesn't function properly, there are likely defective components that will need to be replaced.
The differential amplifier has two inputs. Th differential circuit can be in the form of multiple discrete components or the inverting/non-inverting inputs of an op-amp.
Most of the Chinese and Korean class B amps use discrete components. Most class D amps use op-amps.
In the attached image, you can see a differential amplifier circuit at the front-end of the amplifier circuit. Input is driven into Q101. Feedback of a fraction of the signal from the output of the amplifier is fed-back into Q103. The circuit continually compares the signal at the base of Q103 with the input signal and the differential amplifier instantaneously modifies the drive signal to ensure that the output is undistorted (up to the point where the amplifier is driven into clipping). Without this feedback/servo correction, the amplifier circuit would have to be MUCH more complex and expensive to produce clean (low distortion) audio.
The operational amplifier page of the car audio site has information and interactive demos the help you learn more about op-amps.
Most of the Chinese and Korean class B amps use discrete components. Most class D amps use op-amps.
In the attached image, you can see a differential amplifier circuit at the front-end of the amplifier circuit. Input is driven into Q101. Feedback of a fraction of the signal from the output of the amplifier is fed-back into Q103. The circuit continually compares the signal at the base of Q103 with the input signal and the differential amplifier instantaneously modifies the drive signal to ensure that the output is undistorted (up to the point where the amplifier is driven into clipping). Without this feedback/servo correction, the amplifier circuit would have to be MUCH more complex and expensive to produce clean (low distortion) audio.
The operational amplifier page of the car audio site has information and interactive demos the help you learn more about op-amps.
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I've read your page 200 times.I even bought the DVD 5 years ago and can't find it.Probably will purchase the online version.I'm learning alot about the power supplys,output FETs,drivers etc.I have to start diving into the op amp and audio side of things.
BTW,can the power supply cause DC offset issues?
BTW,can the power supply cause DC offset issues?
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