Yes happylad you are correct. My confusion arose because I had recently become familiar with the history of the RIAA phonograph curve. At one time both a NAB eq curve and the RIAA curve existed separately though there was only a difference of 2db or 3db in the roll off at one of the specified frequency points. The NAB curve really caught on at the tail end of the 78 era.
Long before Stanton produced the 310B the NAB and the RIAA were on the same page regarding phono EQ / compression and the RIAA curve was adopted.
The NAB produced test records designed to enable checking the phono chain from turntable to either the tape out of the preamplifier or the phono stage output depending on system configuration.
After reading the 310B manual and the following description of testing it is clear this unit was designed from the standpoint of a using a NAB record to test RIAA conformance and to enable as much adjustment and correction as possible. A NAB test record is so essential to the highest functioning of the 310B that it is labelled NAB and not RIAA, though this also may have been customary in professional audio.
I've found a number of sites that explain what the RIAA curve is and how important it is, but no instructions on checking it. However, I can tell you how to check it.
You will need a NAB disc and a decibel meter. The NAB Test Record NAB-1 is a vinyl record with a series of frequency tones on it from 30cps to 15,000cps. Put the NAB disc on your turntable and connect the decibel meter to your "Tape Output" on your preamp, if it has one. If there's no "Tape Output" the second choice is the "Main Output" with all tone controls "OFF". If you're using a separate phono preamp, then connect to it's output.
Use the 1,000cps tone on the disc for your "reference". Whatever dB reading this tone gives you, this will be your zero or reference tone. All other readings will be considered above or below this mark and labelled plus or minus by so many dB. A perfect system will give the same dB level reading at all the test frequencies. However, in this real world, you will be doing good to have the frequencies stay within plus or minus 2 dB in many cases. If you go outside of the plus/minus 2dB then I recommend trying to correct it. If you're within the 2dB you can try to get it better and see what happens.
Please keep in mind that you are testing the actual functional response of the cartridge, cables, RIAA compensation loop, and preamp. All of these items can be "working properly" and still not give a flat response due to the capacitance and resistance of the cartridge loading. That is why it's so important to check the RIAA playback response with an actual Test Record. The manufacturer of the preamp or cartridge may publish the specs on it's RIAA playback response as being plus or minus 0.00001 dB, and it may in fact meet those specs. But this is the capability of the preamp to play the exact RIAA reverse response curve to the curve on your records. You will never get the NAB Disc to play back that flat. So, for other perfectionists like me, don't drive yourself crazy trying to get the NAB disc to play back flatter than is reasonably possible.
It seems these NAB test records have not been produced in eons but I found the following comments regarding setup using the NAB record and "The Ultimate Analog Test Record".
I use the Ultimate Analog test record.
When I bought my Lathe from Al we ran through the calibration together using a NAB disc.
When I got my lathe home I ran through the calibration on my own using the Ultimate Analog disc. The final values on the amp rack were exactly the same after the subsequent calibration as they were when I brought it home.
Obviously the two discs are not identical. But, they seem to be very close. Otherwise I think I would have derived very different settings after calibrating with the Ultimate Analog.
To summarize a NAB test record or the equivalent Ultimate Audio are an essential component to unlocking the very considerable capabilities of the Stanton 310B.