Phew! I think I need to attend a uni course in audio engineering to understand all this. Most of this went way above my head!
Thanks a million for your thorough advice, mshilarious.
Be prepared for a lot of stupid questions along the way...
I've got this multimeter, but I have no idea if it's RMS capable:
Regarding the dummy load, can I use my multimeter to apply resistance between the pins??? I don't have any resistors lying around
Or for feeding the preamp with a test signal, I can use a 3,5mm stereo>dual XLR cable and connect it from the computer line out to the pre inputs?
Using Wavelab as a signal source (Tools/Audio Signal Generator), create a 1kHz sine wave. Route that out of your interface and calibrate to 1VRMS.
How do I do this calibration? In Wavelab? Heck, I'm not even sure I know what 1VRMS is...
OK, so try setting the level at -30dBV, and send that to each unit. Note that for the balanced input units, you need to have pin 3 terminated to get a valid measurement.
Another stupid question: how do I terminate pin 3? On the pre? At this stage, isn't the XLR connected to the cable? Do I need to open the pre and measure from within the box while it is connected?
It's best if you can route a differential test signal to the unit, if your interface has balanced outs.
How do I make the signal differential (and what does it mean in layman terms)?
Note that you need to measure output between pins 2 and 3 (or tip and ring) to calibrate to 1VRMS, but for the unbalanced input pres you'll have measure between pins 2 and 1 (tip and sleeve).
This is the output of the pres, right? Not the output from the computer??? Again, the calibration parts is a bit hazy for me.
Set each pre to minimum gain and measure the output voltage from the pre.
Between which pins do I measure the output voltage? Since the output is joint 3,5mm stereo, does this measure one channel at a time, or both somehow?
Compare with the 1VRMS level (you can use a loop from the output to the input of your converter to calibrate that).
The converter - is this my computer basically, or a separate piece of gear I should get?
So during all these tests, it's just the PC + pre + multimeter? No mics or recorder involved yet?
Once I've digested this, I'll probably have more questions on the second part of the test...
Again, thanks for your patience mshilarious. And if anyone else has explanantions or opinions, chime in!