Hopefully you’ve noticed that when the engine is accelerating, the exhaust volume increases and the rod clank volume decreases. And when the engine is braking, the opposite occurs - the exhaust volume decreases and the rod clank volume increases. You can use CVs 181 thru 184 to limit how much the volume levels will increase or decrease. During acceleration, CV 182 controls the rise in exhaust volume and CV 183 controls the drop of rod clank volume. A value of 255 for either CV produces the maximum amount of volume change. Lower values result in correspondingly smaller levels of change and a value of zero results in no change at all.
When the locomotive is braking, CV 181 determines the reduction of exhaust volume and CV 184 controls the rise of rod clank volume. As with the other two Volume Limit CVs, a value of 255 results in the maximum amount of volume change. Thus, the upper and lower volume limits of a given effect can be independently adjusted. You could for example, set CV 183 and CV 184 to zero so the rod clank volume is always constant. Setting CV 181 to 250 and CV 182 to 64 results in an exhaust sound that increases volume four times under acceleration but only drops 30% during braking. Try experimenting with different settings to see what the results are.
DDE Timbre and Cutoff Control By changing the value in CV 185, you can change the tone or timbre of the exhaust chuff. A lower CV setting results in a deeper chuff.
Note that the exhaust cutoff automatically increases as the throttle increases. This helps keep the individual exhaust chuffs crisp and distinct as the chuff rate increases. You can control how much change to the basic chuff occurs by varying the setting of CV 186. A low value results in only minimal change and maintains a strong deep chuff regardless of locomotive speed. At higher speeds however, the chuffs may begin run into each other resulting in a strange whirring sound. This can be corrected by programming a higher value into CV 186. In general, the faster you are planning on operating your engine or the higher you have set CV 116 (Auto Exhaust Rate), the higher a setting you will need for CV 186 to maintain the proper exhaust cutoff over the locomotive’s speed range. Try setting CV 186 with different values and observe the effect on the exhaust sound over a range of throttle settings. When properly set, you will get a nice clear exhaust bark over the entire speed range of your locomotive starting with a deep “woof-woof-woof” at low speeds that gradually transitions to a light “chi-chi-chi” sound at high speeds.
Load Sensitive DDE
The DDE and its effect on the exhaust sound can also be varied by changes in the locomotive’s load such as the number of cars being pulled or the grade being climbed. The DDE accomplishes this by measuring the motor’s back-emf voltage which is proportional to the locomotive speed. When the locomotive load increases, the motor speed drops as does the back-emf voltage drops and the DDE interprets this change by increasing the exhaust chuff volume and deepening the exhaust tone. When the load is reduced
Tsunami Steam Sound User’s Guide