I repeated this procedure using a Waves CLA-76 instead of the PC-76. 
 
It behaves exactly the same, except there's more "noise", if that's what it is. The CLA-76 noise floor was about -70db. The Sonar model seems to be much cleaner, but since I can't hear either of them it's a moot point.
 
Do you think folks will start testing their plugs to see which ones are the cleanest? This could be the next micro-niche? This could change everything. 

brundlefly
I checked the PC76 at 44.1kHz instead of my usual 48kHz, and the fundamental dropped proportionally from 187 to 172Hz. If it were a deliberate emulation, I would expect the spectrum to be independent of sample rate. I'm not sure why Ben (Kylotan) doesn't see the lower fundamental that I get at 44.1kHz. I see the same spectrum in Span as in SONAR's PC EQ flyout (with sufficient amplification added); it seems like the fundamental he sees is the first harmonic at approx. 3x  the fundamental that I get. Maybe some Span setting is causing it to be missed.

I agree it should not be behaving that way;
48kHz/44.1kHz = 1.088
1.088 x 172Hz =  187Hz

Everyone here refers to PC76. I got noise from PC4K as described above but never used PC76 before. I was not testing PC4K for noise I simply heard something irritating and eventually found the noise gets lower and then disappears when I switch off every instance of PC4K. So in my case it was not too low to mention, with only c. 20 instances, can't remember the details exactly it was one month ago. Are PC76 and PC4K equally noisy?

As posted earlier, I'm not seeing anything from PC4K with no input. Pictures or it didn't happen.