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Author Topic: DUAL-FFT and signal-source  (Read 7382 times)

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zed

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DUAL-FFT and signal-source
« on: January 19, 2011, 06:08:44 AM »
hello
there is a thing I don't understand (or maybe I'm doing wrong and can't find the reason)
I do a very simple measurement
so, say:
 on my sound-interface the source output is OUT-2
the measurement input is IN-2
a strap is relying OUT-2 to IN-2 (no monitoring, neither internal routing between ins and outs)

I launch DUAL-FFT-Analyser
in the Tab called Excitation I configure OUTPUT-2 (with pink or white noise)
I start the thing and measuring MAGNITUDE" between output2 and input-2 gives me some good results (even with low FFT-Size) showing the performance of my sound-card (preamp and converters)

but when I mute the internal excitation and I launch for example Signal-Generator (or another source from my computer) with pink or white-noise routed to the same output-2, the thing is absolutely not the same....

there is an incredible noise showed in the graph.... its just wild noise !!
it seems not to "hear" correctly the output-2
but if the external signal is on out1 and out2 (for exemple), the measuring between these two source works (= a straight-line!)

maybe there is an issue with the time factor (converters DA-AD via internal routing...)

maybe there are some explications
thanks in advance !!
(just for info: basic measurement knowledge is no problem for me ;it's part of my job and  I know very well softwares like Systune, Win-MLS and Smaart or Room-eq-Wizzard and others
I am into tests in Demo-Mode... maybe some functions are disabled ??
« Last Edit: January 20, 2011, 01:57:08 AM by zed »

FaberAST

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Re: DUAL-FFT and signal-source
« Reply #1 on: January 20, 2011, 04:42:10 PM »
Hi zed,

Have you checked to be sure that you have the same output device and the same output channel selected in the Signal Generator tool, that you have selected in the Dual FFT Analyzer?

In the Dual FFT excitation tab, are you using random or pseudorandom noise?

In the Signal Generator, are you using random or pseudorandom noise?

Ben

zed

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Re: DUAL-FFT and signal-source
« Reply #2 on: January 21, 2011, 01:59:15 AM »
In the Signal Generator, are you using random or pseudorandom noise?
Ben
hy Ben
thanks a lot for this response that permitted me to fix the thing
there were no worries about configuring of INs and OUTs (all correct)
but I used RandomNoise in the Generator and obviously that doesn't work

now I see that it is possible to choose Pseudorandom Noise also and when configuring the correct FFT-Size in the generator (same as in Dual-Analyser) it works very well

thank you very much... I got the thing fixed now !!!
these tools are really well designed and they work well; I love it

a little personal observation:
I would like to get in the windows-menu a Tile and Cascade feature
and maybe even keyboard shortcuts for the windows (to bring one into the front - like in most DAW or other softwares)
« Last Edit: January 21, 2011, 02:09:56 AM by zed »

FaberAST

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Re: DUAL-FFT and signal-source
« Reply #3 on: January 21, 2011, 03:43:08 PM »
Quote
these tools are really well designed and they work well; I love it

a little personal observation:
I would like to get in the windows-menu a Tile and Cascade feature
and maybe even keyboard shortcuts for the windows (to bring one into the front - like in most DAW or other softwares)

Thanks for your feedback, zed. I'm glad you have the DFFT analysis working, now.

Ben