Saving loopback calibrations

[ajs123]

I'm wishing to save calibrations made by selecting "Make calibration data from loopback response" in the Measurement screen, as separate calibration files. What I've done is...

1. Take a measurement with "Make calibration data from loopback response" selected.
2. Save the measurement as .mdat.
3. Load the measurement and remove the soundcard cal
4. Use Trace Arithmetic to get A/B, where A is the measurement with the cal removed, and B is the original from step 1.
5. Export the result of step 4 as .frd/.txt

Is that the most effective/efficient way?

 

[John Mulcahy]

No, select the loopback input and output and use the "Calibrate soundcard" and "Make cal file" buttons on the soundcard preferences.

 

[ajs123]

Thanks, John.

"Calibrate soundcard" and "Make cal file" is what I did first. I didn't get the expected result, thought it was possibly because doing "Calibrate soundcard" involved switching inputs, so I was looking for another way.

Followup question: Can you verify that, within reason (neither down near the noise floor nor clipping), the cal does not depend upon precise adjustment of the loopback input?

 

[John Mulcahy]

Can you verify that, within reason (neither down near the noise floor nor clipping), the cal does not depend upon precise adjustment of the loopback input?

Shouldn't matter, but you can always try a few measurements at different gains to see if the interface cutoffs vary. With some interfaces the input impedance varies with the gain setting, but usually the output impedance is so low (relatively speaking) that the effect is very small.

 

[ajs123]

Thanks. The truth is that I'm going through all of these efforts in part to understand what went wrong (good reason) but also avoid having to re-take data (poor reason in the long term!).