Can I subtract a measurement from another ( difference ) ?

L

linuxonly

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Preamp, Processor or Receiver
Logitech Z906
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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
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X11/VGA + X11/DVI
Hi,

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

redmountain

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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

John Mulcahy

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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.
 
R

redmountain

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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
 
L

linuxonly

Member
Joined
Jul 27, 2024
Posts
108
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
redmountain said:
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
Click to expand...
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
 
R

redmountain

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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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