Can REW be used to measure clipping?

AustinJerry

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Jun 5, 2017
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I am involved in a discussion WRT determining the correct output voltage setting for a processor. The recommendation is to experiment with various settings and observe when the output is clipping. I don't have an oscilloscope, and would prefer not to spend the money to buy one. Can REW measure the pre-out signal to determine when there is clipping? If yes, is there a discussion of how one might do this? Thanks for any direction.
 

John Mulcahy

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REW has a scope, but you'll need to be careful to make sure the soundcard input isn't where clipping is happening - the pre out may well have a greater voltage range than the soundcard input. To get around that you would need an attenuator at the soundcard input, using a pair of resistors or a potentiometer.
 

peter08

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Sep 10, 2019
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I may also want to do this, so question: do we detect the clipping by running a pure sine wave and visually checking for when the peak starts to flatten? Or should we check for distortion artifacts on a FR plot?

Also, what sort of frequency would you choose - the default 1kHz or something else?

I also plan to compare the onset of clipping in a couple of power amps (using a 300W resistor bank), and my inclination was to select a low frequency sine wave for that test (maybe 40Hz, instead of 1kHz), based on "gut feel" that a power amp is more stressed driving low frequencies. But then, power calculated from a voltage sine wave does not depend on frequency, so maybe any frequency sine will do.
 

John Mulcahy

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If the system being tested has any EQ gain then best checking at the frequency where gain is maximum. Another way to check is to use the RTA and look for the odd harmonics coming up as clipping occurs, the transition is usually quite distinct as level increases. A stepped level test could be used as well, using the THD limit option to stop the test when distortion gets too high.
 

Foundation

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May 23, 2017
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I'm interested to follow your experience with this Jerry. I'd love to understand my own signal chain better.
 
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