This is not a plugin job. Either a dmm or amm will work. It is essentially the same as dialing the old vu meters.

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Chris, all professional equipment with VU meters are generally calibrated for +4 DBM into a 600 ohm load. And that equipment generally is specified that its maximum output level is capable of +24/+28/+30 depending on the equipment and output transformers utilized. VU meters are just average level devices and every engineer knows that if they are averaging around -6 to -12, your peak program content is at least +15 DB above that even though the VU meters will never indicate that. PPM meters, popular on British equipment and in Europe are calibrated more like digital meters where peak 0 (zero) may well be +24 DBM or 28, or 30. And those VU meter calibrations should not be messed with nor varied except to check their calibration with a 600 ohm resistor on the output for 1.25 V which equates to +4 DBM.

Now the input to your digital stuff is of course different. So if you really want to calibrate something, I would say apply a 1 kHz sine wave to your analog audio gear. Crank up the output to +24 across a 600 ohm load (The actual voltage value has escaped my 56-year-old synapses, sorry. If I could only find my Ballantine DB to voltage slide rule?). Then turn up the input to your digital audio interface until that 1 kHz sine wave sits at 0 (zero) DBFass (DBFS). And voilà, you are calibrated. But of course if the output of your audio device (such as the API which has 3 secondary windings to allow all three of those standards) is that +28 or, +30, you'll want to calibrate that accordingly to 0 DBFS. For instance, on the output of my 3124 API's, the microphone preamp XLR output is connected to 2 of the secondary output windings yielding headroom to +28. While the 1/4 inch outputs are on a single secondary winding yielding only +24 output capability. Ha! Only +24. And I will indicate that no Avid/Digi crap can handle a +24 line level input without clipping everything at the input even if the pad is engaged. And that's proprietary? Proprietary what? Proprietary incompetence I think? So that piece of crap won't interface with my Neve without an in-line resistive pad. But my $80 EdiRol, UA-1 EX, has no problems handling a +24 output from the Neve on its RCA unbalanced inputs. And there is nothing proprietary there so it works well. Even the MOTU 2408 doesn't like to see much anything over +20 and there are no input sensitivity controls to adjust that. I simply refuse to install 4 DB balanced input pads on its 8 inputs. So I have to be a tiny bit more conservative when I feed it from the Neve. But the M-Blotch 2 is just a no can do from the direct Neve outputs. And they don't want to supply me with a schematic so I can fix it. So screw them. Although I will probably end up with Pro Fools 9 or 10 in the not-too-distant future? Maybe then, I'll start to use it more often? I mean even my M-Audio Transit seems to be able to handle a higher input level than the M-Blotch 2. WTF is with that? Even talking to those Avid Fools in person at the AES was absolutely no help whatsoever. There is nothing professional about that.

I guess I'll stop now?
Mx. Remy Ann David