Mike; It looks like you
would not mind to
experiment,so try
changing the .0022 to a
.022 cap [on the plate]
change the 33k resistor
to a 56k and the little
500pf to a 250pf this
will change the lead to a
bass amp marshall,when
you change the feedback
resistor with this mod
switch you installed,I
think if you listen, you
will find that you will
not have as much
volume range,in other
words if you have the
27k on at the time you
will be able to turn the
volume knob further
before it starts to
distort,if you switch to
the 47k, it will distort
earlier,and as you
change further[56k 68k
100k] you will barley
have to turn the volume
before you get
distortion,not much
room for any clean
sound.Also if you took
off the 500pf across the
470k resistor you may
want too put it back
after changing to the
bass amp mod.I think
you said you removed
the .005 on the volume
control,you may want to
put it back,or change the
value for a gain
boost.You should not
disconnect the presence
control,If I remember
right your amp won't
work, if its just
disconected,check this
pots value,also for a
mid boost change the
25k pot to a 50k pot[Big
difference in sound]
Check all your resistors
to see if they have
changed value,this will
effect the amp alot if
they are not in the range
they are supposed to
be.Your feedback wire
should be connected to
the 8 ohm leg of the
output if your useing
EL34s. I hope this will
give you some help.
[Richie]

Steve; What would you be
tring to do, make the bassman
more like a marshall? Most
of the fender is the same
except for the cap sizes on
the preamp plates,[.02
bassman,.022 marshall]and
the bassman having the 270k
and the marshall having the
470k with the 470pf cap
across the bright channel,you
could change the feedback
resistor to 47k on the
bassman [from the org.
27k]for a little more poop!
And put a cap across the
volume control,you can play
around with this to get one
you like, .004, or what
ever,some use these on a
swith for a boost.The mid
mod would be the same,[if
you like it] put a 50k in place
of the 25k.The same for the
tone too, both look like they
have the same 56k with a
250pf cap,[more bass] if you
want less change it to a 33k
with a 500pf cap. The driver
circut should have low
tolerence resistors[2%] on
the 1 megs and 470 ohm. And
make sure the .1uf cap is a
good one.If you do change
this, put a 7025 in place of
the 12AY7. Try this for a
start.[Richie] one other thing
is check the resistors on the
input jacks make sure they
are 68k and 1meg to ground!

You might try using a large series
resistor(100-220k) for the FB but bypass it
with the series combination of a smaller
resistor(27k) and a small cap(.005uf-250pf).
That way the feedback for the higher freq's
will be increased thus reducing their gain but
you'll still get a gain boost at the lower freq's.

Gary