First I have to say I like Aguilar stuff a lot!!! I had DB680, DB659 and two GS112 but I sold it and I kept only AG500 with GS212. I can use this rig in every situation. These days I use Walkabout Scout 12“ for small clubs and AG500 and GS212 for everything else. WA head also works perfectly with GS212. Back to AG500… I have this head for cca three years and never had any problems with it. If something happend and I tought AG500 died it was something else …cables or effects it was never Aguilar‘s problem. Few months ago I heard time to time some noise when I touch jack pluged in, specialy in „stand by“ mode and amp had less power…I thought it‘s bad input but my technician found inside amp one capacitor and one resistor torn off from the printed circuit (one leg of each). I fully understand why it happend. Sometimes rack case roll down and there is still big vibrations while bass playing. My technician was supriced AG500 can runn with these defects. So my AG500 is fixed now but I found one interesting thing. I put back knobs on and I adjust my standard EQ settings and than „wow!“ the sound was fatter, tighter and way louder…I set EQ flat only high midds on 1 o’clock… I had to set flat OBP3 in my instrument becouse there was much more bass and juice so I don‘t need boost bass frequency on my instrument. Than I found why…It‘s hard to place knobs on potentiometers to have flat position strictly verticaly. Faktory knobs placing has center of pots on (cca) 1 o’clock!!. After this repair I placed knobs otherwise centered little before 12 o’clock becouse I thought it was like that before but it didn‘t. There is not chance to have center in ideal vertical position but I think my instalation is closer to vertical position. So that’s why my amp sounded surprisingly different. My amp also sounds better becouse is repaired of course but more important for the sound is new „true flat“ setting…Now I feel my AG500 sounds great „set flat“. I remember some reviews where users say that AG500 sound little sharp so just try „real flat setting“ and you will see what happen. For me it’s huge difference. If you check pics of AG500 (black version) from e-shops or Aguilar site knobs are set on 1 o’clock brown version of AG500 is set on 12o’clock…just a pics? I feel that I found real power and right sound of this great unit for me. I hope my thread can help somebody (or everybody already knows it?! ) Maybe I’m mistaken maybe I’m wrong or maybe it’s common but I didn’t knot that. You can may say: „just use your ears for EQ setting“ but I think it’s good to know where is right flat EQ position setting…maybe this factory setting is just right and I’m just crazy than I‘m sorry……I hope you understand my english ...W.