For the purposes of setting up the DDE, we suggest you start with the DDE CVs set to their default values. Set the exhaust (CV 131) and rod clank (CV 135) volume levels to their default values of 128 and 32 respectively. Then set CV 3 and 4 to a value of 40 to enable the momentum. For the time being, disable the DDE by setting CV 177 and CV 178 to zero. Note: The value for CV 3 and CV 4 is selected for demonstration purposes only. Once you have the DDE ‘tuned up’, you can go back and set CV 3 and CV 4 to a lower or higher value as desired.
Next, place your locomotive on a section of track that is sufficiently long enough for it to “stretch its legs” and get up to speed without worry of running into something. If you have them, a set of stationary test track rollers also works well. Crank the throttle up and take note of the exhaust chuff volume and tone.
Bring the engine to a stop and re-enable the DDE by setting CV 177 to 10. Crank the throttle up again this time to a speed step somewhere around 40 or so. Now, as the engine accelerates, the exhaust chuff should have considerably more volume and a deeper tone.
Allow the engine to get up to speed and notice that the exhaust sound gradually returns to its previous level. Then quickly turn the throttle down. You should hear a sudden drop in the exhaust chuff volume along with a reduction in bass level and an increase in the rod clank volume. As the engine slows, the sound levels will gradually return to their normal level. This is the basic Throttle Controlled DDE action. Once you have the DDE responding to the throttle, you can begin experimenting with the various CVs.
Throttle Sensitivity Try changing CV 177, Throttle Sensitivity to a value of 1 (low sensitivity). Turn up the throttle to speed step 40 and allow the engine to reach ‘cruising’ speed. You can modulate the exhaust sound volume by turning the throttle up or down but observe that a relatively large throttle change is needed to get a big change in volume. Now set CV 177 to 50 and again, bring the locomotive up to speed. Note that this time, with a high sensitivity setting, only a slight wiggle of the throttle around step 40 is needed to bring about a large change in exhaust volume.
Attack and Release Times As previously mentioned, CV 179 and CV 180 control how fast the DDE can react to a load or throttle change. Try setting these CVs to 250 for a very fast attack/release time. Set the throttle around 40 and allow the engine to reach speed. Vary the throttle above and below speed step 40 and you will hear the volume levels change almost instantly in response to changes in the throttle setting. Now set CV 179 and 180 to a more moderate value of 5 and try again. This time when the throttle is changed, you should hear the sound transition more gradually from one level to another and very rapid changes of the throttle are almost ignored.
Tsunami Steam Sound User’s Guide