spike on Mesa Mark series amps that cant be dialed out. Kinda hard to smooth out the sound on my Mark 3 since any bass adds flubbyness and the treble seems a tad bright. So I crank the mids and reduc ethe bass to 1 and treble to about 3. But the amp still sounds alittle ice picky, wish I could smooth out the 2khz range a bit without having to use any external eq. Its funny cause I love John Pettrucis lead tone and I had a Mark iv for awhile and tride is settings and they did not at all sound like anything on the systematic chaos CD. The tone I was hearing was bright and harsh with no body or definition.