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Advanced Programming

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’.

Tsunami Steam Sound User’s Guide

Page 52

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