[jbreher]

Thanks for the continued discussion.

Originally Posted by Darryl Ramm

You explained what you are setting the plugin to but you never explained **exactly** how you are measuring the output value?

OK.

Do you have an actual VU meter? Or are you measuring voltage? What *exact* device are you using

No VU meter - that seems yet another variable that would require calibration first. I am measuring voltage. I am using a Hewlett-Packard 973A handheld true RMS DMM. The probes are across hot and cold of each channel in turn. At least for the outputs. The input calibration -- as per the procedure defined in the HD I/O User Guide -- employs the internal SW metering with the previously calibrated outputs.

and what exact level are you looking for?

I am seeking to calibrate to -18dBFS corresponding to my nominal operating level of 0VU or +4dBu.

Are you factoring in load impedance corrections?

No. I am measuring open-circuit levels on the outputs (or rather feeding the high Z input of my DMM). My assumption is that the output Z of the HD I/O is low enough in comparison to the input Z of any input I might feed with it so as to have a negligible effect upon the output voltage.

You want what calibration level?

The factory setting of nominal 0VU or +4dBu corresponding to -18 dBFS is what I would like to calibrate to.

dBFS is always peak... from the literal meaning of "full scale" So if you can really measure 0VU on a real VU meter then set the signal generate to use peak--the template was correct.

Yeah, I think I came around to that conclusion. With the exception that it was set up for a calibration level that does not correspond to the factory settings (i.e. -20 dBFS rather than -18 dBFS). I understand that there are numerous environments where -20 is more appropriate, but it just seems odd to ship a cal template that is in conflict with stated factory setting.

There are no other things to think about

Manifestly, the results differ -- at least following the procedure in the user guide -- whether one employs Peak or RMS measurement of the signal source. As it should.

Thanks for your help.