as might happen when going downhill, the motor speed rises along with the back-emf voltage and the DDE lowers the exhaust volume (and raises the side rod clank volume). Before you can use the Load Sensitive DDE feature, you will need to decide if you are going to use Tsunami’s load compensation feature or not (see next section) as the set up procedure is slightly different depending on your choice. On most locomotives, the Load Sensitive DDE effect will be more dramatic when load compensation is disabled. This is because load compensation, by design, keeps the motor speed stable and thus the DDE does not detect much of a load change.
Setting the DDE with Load Compensation On If you decide to keep the load compensation enabled, then setting up the DDE to react to load changes is mostly a matter of adjusting CV 178, Motor Load Sensitivity. You can demonstrate that the feature is working by setting the throttle to some nominal speed and slowing down the motor by rubbing your finger against the flywheel (or a driver wheel if you can’t reach the flywheel). As the motor slows down, you should hear the exhaust chuff deepen and increase in volume. Increasing the setting of CV 178 will make the exhaust sound more sensitive to a given change in the motor load and speed.
You will likely find that in practice, your finger is able to exert a much greater load on the motor than will be experienced when the locomotive is simply running around the layout. This is due in part to the relatively high gear ratios and light weights found in the average model locomotive. On a layout, when too great a load is encountered the locomotive will slow down only slightly and then the wheels will break loose and simply start spinning away. Thus, Tsunami only senses a slight change in the motor load.
This means to get a reaction in the DDE, you will need a relatively high setting for CV 178. As you increase the sensitivity setting, you may also notice the DDE starts to react to minor variations in track or even slight binds in the locomotive mechanism. To counter these effects, you will need to reduce the attack and release time constant settings in CV 179 and 178 which will slow the DDE’s reaction time enough to ignore minor ‘hiccups’ in the motor load.
The following procedure may be helpful in finding the correct DDE settings:
Use the throttle Controlled DDE setup described above to find the desired settings for CVs 181-184 and CVs 185-186. Set CV 179 and 180 to about 30 for a relatively quick attack and release time.
Set CV 178 to an initial value of 5 and use the ‘finger test’ to see how the DDE reacts to a large motor load change.
Once you are satisfied the DDE is reacting to the motor load, place the locomotive on your layout, connect up a medium size train and drive it around and listen for a response to changes in grade and load. If no response is forthcoming, increase the setting of CV 178 by about
Continue to increase CV 178 until you can detect a change in the exhaust sound.
Tsunami Steam Sound User’s Guide