I am hoping other TH users can shed light on the Mid Frequency ("MF") knob. I feel like adjusting the MF knob only introduces very subtle variations in tone. Honestly, even from completely off to completely dimed, I feel like it is hard to audibly hear much of a difference. I tested this by keeping the Mid Level knob at 12:00, turned the MF knob both incrementally and drastically. I know the soldering joints are in tact because leaving the Mid Level knob off and then bringing up the MF knob introduces volume. I have owned my TH500 for about 3 years, and also purchased it used. I've historically gigged with the two Mid knobs at 12:00, but have recently realized I have fallen out of love with that tone - I'm actually starting to loathe the overall tone, I feel like the low end presence is completely lacking beef and girth, and that the tone is not at all tight and functional. I see YouTube videos of people demoing the TH500, and mine really doesn't sound anything like theirs even with the EQ's identical. I also try to use roughly the same instrument as the demos if I can - I own a P w/ Flats, Jazz w/ Rounds and P w/ Rounds (and I am aware that there are numerous factors that affect tone, i.e cabs, fingers, action height, pickups, etc.) It's possible that I am just loathing the sound of my cabs (2 Aguilar GS 210's), but wanted to see if the MF knob is working properly and is indeed supposed to be very subtle. Something is going to get replaced, I'm just not sure if it needs to be the cabs, the head, or all of the above. As always, thanks for your help!