How audible is it? Well, if I play the audiophile standard Spanish Harlem from Chesky, the bass notes at the beginning are clearly buzzing slightly (as if the speakers were being slightly overloaded.) This is over speakers and from the headphone jack as well. It isn't audible as noise without signal and higher frequencies are not affected. Test tones below say 200 Hz are also audibly affected. Does it reflect the difference in the 2 sweeps with EQ on and off? EQ on shows a hump in THD between 40 and 200 Hz, but still that's only around .02% at 100Hz... doesn't seem reasonable.