By replacing the 6k8 mid resistor with a 56k or 68k resistor (as
mentioned in my post above) there is a substantial boost but the
bass control still has some effect on the sound (unlike removing the
resistor altogether). This was brought up by Bruce Collins a few
months ago and is a refinement over the old Boogie Mark I boost
switch of removing the ground connection from the "tail" of the tone
stack.

Steve Ahola

P.S. Another way to take the tone stack out of the circuit is to
switch out the connections between the treble control and the bass
control. This was mentioned here last summer by Gil Ayan, and the
resulting sound is less muddy than the old Mark I boost (having the
signal reach the treble control through the bass and mid caps and
pot(s) seems to muddy up the sound a bit).