circuitbenders.co.uk CB55 - Revision 1.1
The circuitbenders.co.uk CB55 is an exact clone of the voice board of the Boss DR55 drum machine. It features four
fully analogue sounds, bass drum, hat, snare, and rimshot. There is also an overall accent feature that adds a little
extra punch to the whole mix when it is triggered.
The sounds and accent can be triggered using standard trigger pulses, or with the optional trigger conditioning
circuit you can use gates or trigger pulses longer than 10ms.
What is the trigger conditioning and do I need it?
The CB55 voices are triggered using standard 5v trigger pulses that last for 10ms. Any longer than that and you
may experience double triggering and flam sounds, any shorter and the sounds decay incorrectly. Unfortunately a
lot of older drum machines such as the TR707 and TR606 have a fairly random trigger output length, and gate
signals can be any length, so the trigger conditioning circuit takes any 5v trigger pulse of 10ms or more, and turns it
into a 10ms pulse suitable to trigger the voices.
If you're using a midi to trigger convertor or a modular system where you know that the triggers are 10ms long,
then you can use the TRIG_IN2 connector and leave out all the trigger conditioning circuit (components marked in
red on the parts list). If you don't know how long your triggers are, you want to use 5v gate signals, or you will be
using a mixture of triggers, then its probably better to just install the conditioning and trigger the sounds via the
TRIG_IN1 connector.
Construction:
The first thing to do is read through this entire guide
, make sure you sure you have all the correct parts, and check
the notes section for boards labeled "
R1.1 CW
"
. Then get started by installing all of the resistors, as shown below:
Next install the diodes and if you're using them, the jumper links. The diodes need to be correctly oriented so that
the band around one end of the component body is at the same end as the band shown on the board. D1 is a
larger 1N4001
Summary of Contents for CB55
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