Lobby > Amp and DAC Measurements
Standard Distortion Spectrum Measurements For Amps (Changstar)
Marvey:
I can see CCIF being a good measurement for comparative purposes with other published measurements, but it's useless for the following reasons:
1) Oftentimes we don't know at what load and what voltage/power with other measurements.
2) What Donald said - it's more for academic reasons. There was probably a better reason for this test in 1937 or 1927.
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600/1700 instead of 500/1800 is fine for the alternate 1:1 two tone test.
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60Hz / 7kHz... prefer 2:1 ratio instead of standard SMPTE of 4:1 because 2:1 better reflects spectrum of popular music.
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40Hz is good instead of 60Hz. What Donald said.
However, should we still bother with 20Hz?
ultrabike:
I would bother with 20 Hz. Music with content there may go down south if the amp goes non-linear distortion wild into the more audible bands.
OJneg:
What sort of FFT windowing should be used for consistency? I suggest Kaiser 5 with a larger window for looking at distortion spikes
Donald North:
--- Quote from: OJneg on July 30, 2015, 12:47:32 AM ---What sort of FFT windowing should be used for consistency? I suggest Kaiser 5 with a larger window for looking at distortion spikes
--- End quote ---
I recommend using a common window which is supported on a variety of hardware platforms.
Marvey:
--- Quote from: OJneg on July 30, 2015, 12:47:32 AM ---What sort of FFT windowing should be used for consistency? I suggest Kaiser 5 with a larger window for looking at distortion spikes
--- End quote ---
Well, TBH, the one that looks the best. :-) The QA400 doesn't have that many options as ARTA. I used Hann because it had the least amount of spectral leakage. In terms of FFT window size, the higher the better, until your CPU barfs. Kaiser 5 was good on ARTA, but not supported on the QA400
Rect was the best for obtaining FR based on averaged PN White Noise, all the others have ripples.
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