Can I subtract a measurement from another ( difference ) ?

linuxonly

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Jul 27, 2024
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Preamp, Processor or Receiver
Logitech Z906
DAC
AMD FCH Azalia
Computer Audio
SPDIF output with alsa, pipewire, wireplumber on Fedora 40
Streaming Equipment
Kodi
Front Height Speakers
33 in
Middle Height Speakers
30 in
Rear Height Speakers
57 in
Video Display Device
X11/VGA + X11/DVI
Hi,

It's readily available in the Beta version: Trace Arithmetics -> A-B
 

redmountain

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Dec 8, 2022
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Yes
but
A-B doesn't reflect the actual difference in dB
i.e.100dB@100Hz - 90dB@100Hz I would like to see as
-10dB@100Hz
Hope to be clear...

Thanks

Klaus
 

John Mulcahy

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Apr 3, 2017
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8,099
dB traces are produced from the log of the underlying data, for magnitude responses the trace values are 20*log10(data values). log(A/B) = log(A) - log(B), i.e. division of the underlying data sets corresponds to subtraction of the logs of their values.
 

redmountain

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Thread Starter
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Dec 8, 2022
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sorry, that is to much for me
Thank you anyway !
It would be great for me to have an arithmetic difference shown between 2 measurements, defaukting on a flat 'zero +/- line
Best regards

Klaus
 

linuxonly

Member
Joined
Jul 27, 2024
Posts
112
More  
Preamp, Processor or Receiver
Logitech Z906
DAC
AMD FCH Azalia
Computer Audio
SPDIF output with alsa, pipewire, wireplumber on Fedora 40
Streaming Equipment
Kodi
Front Height Speakers
33 in
Middle Height Speakers
30 in
Rear Height Speakers
57 in
Video Display Device
X11/VGA + X11/DVI
sorry, that is to much for me
Thank you anyway !
It would be great for me to have an arithmetic difference shown between 2 measurements, defaukting on a flat 'zero +/- line
Best regards

Klaus
Hi,

Like John told you in https://www.avnirvana.com/threads/c...ent-from-another-difference.14245/post-107978 , use trace arithmetics -> A/B
Don't tick 'max gain'

Capture d’écran du 2024-10-11 11-10-45.png
 

redmountain

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Thread Starter
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Dec 8, 2022
Posts
29
Thank you
I misinterpreted A-B
A/B means A divided by B here
A-B means A subtracted by B

Sorry...
 
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