Corrected Maestro Bass Brassmaster BB-1
After a great deal of detective work by some effects makers and comparisons with original units, it
has been determined that the manufacturer’s schematic for the Maestro Bass Brassmaster model
BB-1 is incorrect in one small way: the pinout for the darlington device (2N5308) is shown backwards.
This is shown in the corrected schematic below.
The Bass Brassmaster PCB sold by General Guitar Gadgets properly reflects the schematic except in
three ways. These are:
1. The positioning of the Darlington is show according to the original, incorrect schematic diagram. This
can be corrected by turning the transistor 180 degrees in the mounting holes.
2. The nomenclature for R22 and R27 was reversed on the schematic noting the part numbers for the
PCB. If these are reversed, it is then correct compared to the schematic, and has been proven to
work properly.
3. The switching on the filter was simplified to simply put one resistor in parallel with the other. For
instance, instead of switching from 47K to 6.8K, the two were simply paralleled. This makes the
switching much simpler, requiring only a 3PST instead of a 3PDT switch. It does change the filter
frequency slightly, making the high position about 14% higher in frequency. In practice, this changes
the sound of the effect very little.
However... I have updated the PCB layout.
Updates, layouts copyright R.G. Keen 2009. All rights reserved. No permission for local copies or presentation
from web sites other than http://www.geofex.com.
