Dejon Hamann wrote:



> I'm running a Green bullet (sometimes a Shure 58) into an old 60s
Fender

> Bandmaster head (silverface).  I've got 2 single 12 cabs (one half
open, 1

> closed) set about 10 feet away.

>

> I was just wondering how I could get a dirtier, nicely overdriven sound
out

> of this configuration?  The clean sound is wonderful.  I've
got a Boss Blues

> Driver, but I hate the simulation -  Real overdrive is the sh-t,
but this

> amp doesn't have any.  And it's usually impossible to get a decent
volume

> with articulation on the overdrive channel of my Hot Rod Deluxe
anywaze.  I

> love amp heads because I can adjust the amp settings and not have to
stand

> right on the speaker!  Any Advice would be greatly
appreciated.

>

> The bandmaster does have a Normal and Vibrato channel - maybe I could
get an

> A-B box and do something internally to the Bandmasters Normal channel
so it

> would overdrive?  That thought just hit me - not sure if it's
plausable.

>



Try this, it will take the services of a qualified amp tech.  Take
these

instructions to your tech and see if he can perform these steps.  Check
that

filter caps, other componets, etc. are all A-OK.

1. "Blackface" the phase inverter circuit.

2. Install a 5R4 rectifier

3. Change the power supply dropping resistors to a pair of 10K (around
that

value), 3 watt minimum, you're shooting for about 310 volts of B+ feeding
the

phase inverter plate resistors, and 260 volts B+ feeding the pre-amp
plate

resistors.  You may not get the voltages quite that low on a silverface
amp.



Decide which channel you wanna use for harp, if you have no use for the
vibrato

effect, then do the following changes to the normal channel which will have
less

signal loss than the vibrato channel.  If your vibrato channel has a
mid control

(you'll want that) then do the changes on the vibrato channel and if you
have no

use for the vibrato effect, disable the vibrato or replace "Intensity" pot
with

a true shut off type.

Pre-amp modifications:

1. Change grid leak resistor on input to a 5 meg

2. Change 1st triode plate resistor to a 470K 1 watt

3. Change 1st triode cathode resistor to a 2.7K or 3.3K bypassed with a
25/25

cap

4. Change 2nd triode plate resistor to a 330K 1 watt, leave 2nd triode
cathode

stock

5. Change slope resistor to a 56K

6. Change 250pf treble cap to a 100pf silver mica

7. Change output coupling cap to a .047 mfd 400 or 600 volt rating  (it
may

already have this value)

8. Try changing the bright switch cap to a smaller value, say from 50pf to
100

pf

9. Tweak the midrange resistor with a temporary 25K pot until you find a

resistor value that coincides with the resistance value of the pot when it's
set

to tone you like.  I like a very low value or a straight wire to
ground.



If you're not gonna use the vibrato effect, remove the vibrato driver tube
and

vibrato channel pre-amp tube.  If you did the previous changes to the
vibrato

channel (cuz you want to use the vibrato), then remove the normal
channel

pre-amp tube.



Experiment with different pre-amp tube combinations try these in the
pre-amp

tube position:

12AY7

12DW7

5751

12AX7

For the phase inverter position try these:

12AT7

5751

12AX7



I prefer a 12AY7 in the pre-amp and a 5751 in the phase inverter



For power tubes, for more breakup and a midrangier tone use JAN Phillips 6L6
WGB

5881 (prefered)or Sovtek 5881

For more volume and headroom before breakup and more bass response try
the

various 6L6GC types, Svetlanas, JJ's, Electro-Harmonix



Bias the tubes but slightly imbalance the bias so there is about a
7-10ma

difference between tubes



Last but not least try tweaking the feedback loop resistor, try doubling
the

stock value of 820 ohms to a 1.5K, then try a 2.7K, 3.3K, etc. up to around
10K

(or temporarilly use a 10K pot), I like a 4.7K.



Consider getting different speakers, Weber now makes harp specific
speakers

(they're not listed on the website but if you ask Ted he'll take care of
you.)

Better yet build a new cab, try a pair of 8" speakers with a single 15"

speaker.  Weber now makes 12 ohm speakers by special order, 3 12 ohm
speakers

wired in parallel will give you the 4 ohm impedance that a Bandmaster
requires.



Seems like a lot, but other than the speakers and power tubes, the
components

are fairly inexpensive.  It seems labor intensive but a good tech could
knock

this off in an afternoon or evening.



BTW, this is the same setup I have on my Vibrolux Reverb which is very
similar

to a Bandmaster, it kicks ass for harp.



Good luck,

Don D.



P.S. if you live near me I could do the work, but I'm extremely busy at
the

moment, contact me offlist.