Hi
I have done some response of amps
I got the picture in attach
I can’t understand why from 1kHz to the high end the trace became thick
With both sw
Thanks
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Looks like some kind of instability.
It’s quite visible between 200Hz and 1kHz
The test was done on AudioNote Kit III, SEPP of 300B, and the doubt is about the secondary of OT where the 0 terminal is not to ground.
I will check, maybe this is the reason
Walter
More averages and higher fft size?
Try again without using the chirp option
Ok thanks
Walter Gentilucci
+39 335343255
First, what you’re seeing is typical chirp output.
I think you’ll find the latest version (1.4.1) of QA40xPlot does a better job with Chirps due to forcing rectangular fft windows. With that said, Chirps are a low-energy test so there are things you can do to improve the Chirp result.
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Use a longer FFT. This will improve low-frequency results and also improve smoothing results. I’d probably use 256K at your sample rate.
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Increase the voltage. Because Chirp is trying to extract information from a little energy increasing the energy will improve the accuracy some.
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Use smoothing. Even .01 octave will do great things at the higher frequencies without costing any real accuracy.
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Reduce the frequency range. Set the range to cover the area you are really concerned about but every octave of additional frequency range reduces the energy in other octaves.
Finally, for the utmost accuracy, @handsome is correct that turning off chirp and using a standard single-frequency sweep is rock-solid accurate (especially with averaging). It will produce many fewer frequency points so it isn’t as cool and smooth looking (and it is much much slower) but the values may be more accurate at the frequency limits.
Mark
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Ok
Thanks
Off topic: with 40x plot I can’t save the setting of the colors and some other parameters. There is a tab “save on exit” but not working
Any suggestion?
Walter
The colors in the Color Palette (see Edit Palette button) and the 3 environment colors (background, graph background, …) are definitely saved in your configuration.
As a test, change palette entry 1 (the left channel plot color) and ensure the left channel uses it. Then go to the File menu and select “Save Configuration as Default” then restart the program you should see the new color. It works for me.
It should save any changes to that palette when you exit if you have selected “Save on Exit”.
Note that setting it to not save on exit requires you change that setting and then manually save the configuration as default (it’s now set to not save on exit after all).
Mark
you might want to check out: Configurations · MZachmann/QA40xPlot Wiki
I have a similar issue with the frequency response plot with the exponential chirp: Below a ‘few hundred’ Hertz, I see a strange ‘bouncing’ in the plotted response when I am sweeping an audio transformer. Otherwise the transformer seems to have a good freq. resp.
I have tried using a long FFT and averaging, but this is the best I can get. I have also tried adding build-out resistors and terminating resistors in my transformer measurement setup. I have looked with an oscilloscope and cannot see the level(s) bouncing while the frequency sweeps upwards.
I am guessing that it has something to do with my settings and/or the stepping of the frequency sweep and/or the FFT computations, but any help/advice would be appreciated.
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Sorry; I managed to cut off the frequency range of the plot: It displays from 20Hz to 20kHz.
@walge That’s a strange message. Is it possible you don’t have a Documents folder? What happened when you tried to manually save the default configuration? Did that work?
@CharlesM For a chirp that looks pretty good. Some low frequency bounce is not unusual and the smearing and stuff as well. Note that your smearing and bounce are very small values (like 1/10dB) and you’re testing something that sounds inductive hence “bouncy”.
You might try the Frequency Response test in QA40xPlot where the chirp’ed test gives you a bit more obvious tuning of the chirp signal as well as the ability to add smoothing. You can also just do a point-by-point sweep for the frequency response curve there to improve accuracy at the sweep edges.
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Hi
saving the defaulit config it is ok
W
@walge I have no idea. The message you are seeing is directly from the operating system when I ask it to write the new file data in a single line of code (that same line you just tried manually). Is it possible you had it open in an editor at that time so it couldn’t be written to or you were renaming it?
HI
The destination of the .cfg to be saved is not listed on my pc
Hi
with the QA40x sw the print is the alone graph, while with plot there are also on left and right sections the deatils. Is it possible to have also only the graph ?
Thx
@walge the configuration file is always saved to a specific place on your computer defined by Windows. Namely in the Documents folder in your personal library that is created when you install Windows. I’ve never heard of renaming that folder but in any case the path is listed in the error message. When you do a “Save as Default Configuration” it saves the file in the exact same path. You can easily see if C:\Users\walge\Documents is a valid folder.
There is no trivial way to photo just the graph. It’s easy enough to clip the full Photo to the graph boundaries using Paint or I usually just use the Windows Snipping Tool and snip it on-screen then save it. It’s nice to show the left hand side so that you know what your settings for the graph were.
Hi
for the config file I have this path C:\Users\walge\Documents with a folder Quantasylum where inside there is a folder QA40x with inside
That’s nice but it has nothing to do with QA40xPlot. Since the config file is loaded at startup it has to come from a fixed path (based on your Windows session settings) and that is:
C:\users\yourname\Documents\QADefault.cfg
I note that the folder you are pointing to is named Documenti not Documents. Perhaps try creating a folder named Documents in the C:\users\walge folder.