SoundTraxx Tsunami Steam Users Guide - Manual (Page 55)

Tsunami Steam Sound User’s Guide Page 52
response to a load or throttle change. This CV can be set between 0 and 255
with larger numbers equating to a greater sensitivity to a given change.
CV 187 sets the damping factor of the DDE’s filter bank and can be used to
modify the exhaust chuff’s overall tonal shape. Normally, this CV should be
set between 200 and 255. Lower settings may be used but you will find that
the exhaust chuff will begin to take on an unpleasant and ‘alien’ characteristic
as the CV value is reduced.
CV 188, DDE Tracking Coefficient
When load compensation is disabled, the DDE senses the load on the motor
load by comparing the motor’s back-emf signal to a zero-load reference level
as set by CV 188. The setting for CV 188 is based on the motor’s efficiency
level, typically 70% to 80%) and may be calculated as:
CV 188 = Motor Efficiency X 128
Thus, a 75% efficient motor would use a CV setting of:
CV 188 = 0.75 * 128 = 96
Determining a motor’s efficiency requires instrumentation not available to
the average hobbyist so it must be determined via trial and error as will be
discussed shortly.
Now that you have some idea of what each of the DDE control CVs does, the
next step is get familiar with the range of sounds that are possible by actually
trying the DDE out. As the DDE is easier to setup to respond to throttle
changes, it is best to start there.
Throttle Controlled DDE
The DDE responds to changes in the throttle by comparing the throttle setting
to the current locomotive speed. The greater the difference between the two,
the greater the change in the exhaust and side rod sound that will be heard.
When the throttle is increased, the locomotive will begin to accelerate. During
this period of acceleration, the exhaust chuff will grow deeper and louder
while the rod clank volume will become lower. Likewise, if the throttle is
decreased, the locomotive will begin to reduce speed. During this period of
braking, the exhaust chuff will drop while the rod clank volume will increase.
As the locomotive’s speed approaches the throttle set point, the exhaust and
rod clank volume will gradually return to their normal values as set by the
audio mixer.
For this effect to work, some nominal value must be programmed into
the acceleration and braking rate CVs (CV 3 and CV 4). Otherwise, the
locomotive speed will quickly follow the throttle setting and the braking and
acceleration periods will be so short that the DDE will be unable to work its
‘magic’.
Advanced Programming