measure amplitude of modulated signal - diyAudio
 measure amplitude of modulated signal
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diyAudio Member

Join Date: Apr 2002
Location: Munich
measure amplitude of modulated signal

How must the amplitude of a modulated signal be measured, so that it can be compared to an unmodulated signal ?

With the cursor as in the picture ?

Attached Images
 modulation.jpg (80.4 KB, 147 views)

 13th August 2009, 11:58 AM #2 diyAudio Member     Join Date: Sep 2004 Hi, Depends what part you want to measure... the recovered signal, the average carrier or peak envelope power of the whole thing? Cheers!
 13th August 2009, 12:12 PM #3 diyAudio Member     Join Date: Apr 2002 Location: Munich I want to measure the frequency response of a sweep on CD to make corrections on the analog filter for a nonos DAC. @ 20kHz it is already modulated like in the picture, and I am not sure how the amplitude should be to have a linear response. The question might be, what does the ear detect, the maximum peak value or something else ?
 13th August 2009, 12:18 PM #4 diyAudio Member     Join Date: Sep 2004 Ah, now we have this in context, you are witnessing "aliasing" - a beatnote when the sample frequency is (hideously complex math) with the recorded frequency. When I encounter this, I usually try a different playback device The ear detects average and when two signals are concerned, the linear sum. Anybody that can be more helpful, jump in... Cheers!
diyAudio Member

Join Date: Apr 2002
Location: Munich
Quote:
 Originally posted by Geek When I encounter this, I usually try a different playback device
The amplitude of the signal as shown in the picture shall be compared to a clean 1 kHz sine.

So the question is:

Is the response linear if the cursor keeps touching the curve during the sweep ?

diyAudio Member

Join Date: Apr 2002
Location: Munich
Quote:
 Originally posted by Geek The ear detects average and when two signals are concerned, the linear sum.
So RMS would be correct ?

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