Apparently, I didn't get the point across in my previous post. This should be documented in the JVC 402B manual.
On page 28 it describes how to adjust the EQ bands (5) which is basically a more sophisticated tone control. There are 2 bands in the bass region, 1 in midrange, 2 in treble. (+- 8DB). JVC has used builtin 5-band EQ's for years because they are more flexible than simple tone controls.
Five bands can still be limiting (I own several Audio Control 10-bands), but simple bass/treble controls only cover two bands controlling a wider range. In other words, the EQ is more precise and flexible than simple tone controls. Although this digital UI is not quite as easy to adjust as twisting two knobs or the old slider days, it's not that hard. On the upside, you should be able to store a (potentially different) EQ profile for each source, which is not practical with many outboard EQ's.
Also, the JVC's EQ is independant of the Bass boost which is typically around 100HZ (which would be between the two bass EQ bands, 63HZ and 250HZ).
So whoever says that "treble can't be adjusted" doesn't know how to fully operate the unit.