Quoted from the Soundtraxx TSU2 User and Tech Manuals
Notes added by Jim Exler (JE), Nampa, ID October 12, 2022
Dynamic Digital Exhaust (DDE) is one of the most fun effects featured in Tsunami2.
DDE Control CVs
CV 2.503: DDE Load Offset (Default 60)
CV 2.504: DDE Load Slope (Default 150)
CV 2.505: Side Rod Clank Low Volume Limit (Steam only) (Default 0)
CV 2.506: Side Rod Clank High Volume Limit (Steam only) (Default 0)
CV 2.507: DDE Exhaust Low Volume Limit (Default S-255 / D-0
CV 2.508: DDE Exhaust High Volume Limit (Default 255)
CV 2.509: DDE Attack Time Constant (Delay) (Default S-150 / D-215)
CV 2.510: DDE Release Time Constant (Delay) (Default S-150 / D-215)
CV 2.511: DDE Throttle Sensitivity (Default 10)
CV 2.512: DDE Load Sensitivity ( Default S-32 / D-0)
When the locomotive encounters a grade, DDE responds to this by increasing the intensity and volume of the exhaust chuff to simulate the locomotive exerting more power. Similarly, the demand on the motor is lifted when the locomotive starts drifting downhill, which reduces the intensity and volume of the exhaust chuff.
CVs 2.503-2.512 are used to adjust parameters of the DDE processor. DDE control CVs allow the engine sound effects to be modified in response to motor process load and/or speed during operation. You may need to modify default settings to fit the specifics of your installation and locomotive. This section details using DDE control CVs to fine-tune your operation.
JE: Before you do anything, read this entire document to understand the ideas and insure that some of the seemingly unrelated settings are correct.
First, if you intend to limit the top speed of the loco, make those adjustments before running the auto calibrate and set the DDE values to their defaults, steam or diesel, then run the “Auto Calibrate” for the load sensing; CV 2.503 and CV 2.504.
Next, I run the loco on the layout with grades and check the DDE effects. Many times this is all that is needed. If the results are not as expected, the fun begins.
Make a list on paper of the DDE CVs with their current settings. Each time you modify a setting, mark it on your list. POM cannot read back the CV settings so this will remind you of what you have.
Using Program on the Main, adjust CV2.512 to what effect increasing or decreasing has. This is the main control. After that, you can play with 2.503 & 2.504. Be sure to list any changes.
You can try different values for a CV, one at a time and easily reset it to the original value. I recommend that, if you don’t like a new value, reset it to the original before you try something else.
If you use DecoderPro, when you are happy with your settings, set the loco on your programing track and “read” the decoder settings into the program so you can save them in the roster file.
Note: To access Indexed CV Page 2 with CVs 2.257-2.512, CV 31 (CV Index 1) must be set to a value of 16 (default) and CV 32 (CV Index 2) must be set to a value of 2. Set this once each session and it will remain for the session.
Calibrating DDE Load Sensing
CV 2.503 (DDE Load Offset) is used to set the DDE processor’s nominal low-speed load level, and serves as a reference point for the minimum amount of load required to move the model. Entering values from 1 to 254 into CV 2.503 will set the DDE load offset. Increasing the value in CV2.503 will modify the operation of the DDE processor such that the locomotive will sound like it is under a lighter load. Decreasing the value in CV 2.503 will modify the DDE processor such that the locomotive will sound like it is under a heavier load.
JE: Do not allow a value of 0 in this CV.
CV 2.504 (DDE Load Slope) is used to set the DDE processor’s nominal high-speed load level, and serves as the reference point for track speed. The value in CV 2.504 determines the load required to increase the speed of the motor (Tech Ref). Entering values from 1 to 254 into CV 2.504 will set the DDE load slope. Increasing the value in CV 2.504 will modify the operation of the DDE processor such that the locomotive will sound like it is under a lighter load. Decreasing the value in CV 2.504 will modify the DDE processor such that the locomotive will sound like it is under a heavier load.
JE: Do not allow a value of 0 in this CV.
After using auto calibrate to set CV 2.504, if the sound does not change enough with varying loads, try changing the value of CV 2.504 to see if that varies the load sensing to get the desired results. Move in increments of say 20 both below and above the auto calibrate setting and check the results after each change.
If the sound does not decrease when the loco starts downhill or encounters a lower load, try increasing the CV 2.504 value by 20. Try another increase if that is not successful. Once you get the change you are looking for, start reducing the value by 2s until the effect fails. Fine tune from there.
I have found I can lower the sensitivity in CV 2.512 along with the CV 2.504 change and get good results.
We highly recommend automatically calibrating the DDE load offset and DDE load slope. Enter a value of 255 into CV 2.503 at speed-step 1, then enter a value of 255 into CV 2.504 at the average operating speed for your layout will automatically calibrate DDE load compensation.
Ensure the locomotive is on level track when entering values of 255 into CVs 2.503 and 2.504.
Follow the steps below:
Note: If, after the calibration is complete, you feel the need to increase or decrease the sensitivity, you can do this with CV 2.512.
Adjusting DDE Volume Limits
CV 2.505 (DDE Side Rod Clank Low Volume Limit), CV 2.506 (DDE Side Rod Clank High Volume Limit), CV 2.507 (DDE Exhaust Low Volume Limit), and CV 2.508 (DDE Exhaust High Volume Limit) are used to set low and high volume limits for the side rod clank and exhaust chuff sound effects that fluctuate according to the load sensed by the DDE processor. Rather than merely adjusting the volume level, adjusting CVs 2.505-2.508 allows you to attenuate and boost the sound of the exhaust and side rod clank from each effect’s mixer channel volume level. CV 2.506 and CV 2.507 are used to specify the side rod and exhaust sound response at low loads. CV 2.505, the side rod clank low volume limit, and CV 2.508, the exhaust high volume limit, are used to specify the sound response at high loads.
During acceleration and when the locomotive is operating under high loads, CV 2.508 will determine the maximum boost in exhaust volume and CV 2.505 will determine the maximum reduction in rod clank volume. A value from 0 to 255 may be programmed into each CV. Under very high loads, the exhaust volume will be amplified by +12dB when CV 2.508 is set to 255 and the rod clank volume will be attenuated by -12dB when CV 2.505 is set to 255. A value of 0 indicates sound volume will not be adjusted in response to throttle increases. During deceleration and when the locomotive is operating under very low loads, CV 2.507 determines the maximum attenuation in exhaust volume and CV 2.506 will determine the maximum boost in side rod clank volume. Under very low load levels, the rod clank volume will be amplified by +12dB when CV 2.506 is set to 255 and the exhaust volume will be reduced by -12dB when CV 2.507 is set to 255.
In summary, CVs 2.505-2.508 allow you to adjust each sound effect’s low and high volume limits to match your preference. For instance, setting CV 2.507 to a value of 64 and CV 2.508 to a value of 255 will make the exhaust 12 dB louder during acceleration and under very high loads, but will only attenuate it by 3dB during deceleration. You can try this with the side rod clank volume as well by programming CVs 2.505 and 2.506 with the same values.
Be careful not to set the baseline volume level too high or too low as the DDE cannot increase or decrease the volume beyond its maximum or minimum settings of 0 and 255 regardless of how high you set CV 2.505 thru CV2.508. In other words, even though the DDE can increase the exhaust volume by up to 4 times (400% or +12dB), if the mixer level is set to 255, no further increase will occur. Similarly, if the mixer is set to 128, then the maximum volume change possible with the DDE is 255/128 or about 199% (+6dB).
JE: If the sound level seems to stay at the high limit constantly, try reducing the volume limit value. The sound may be maxed out and saturated.
Adjusting DDE Time Constants (Delay)
CV 2.509 (DDE Attack Time Constant) and CV 2.510 (DDE Release Time Constant) are used to determine how quickly the DDE processor reacts to changes in load and speed. CV 2.509 determines the duration of time that elapses from when the decoder receives a new throttle command (or senses a change in load) to the time the DDE processor begins to reshape the audio signal. CV 2.510 determines the duration of time that elapses between changes in the way the DDE processor reshapes the audio signal. Longer response times (higher values) may help to ‘smooth out’ the DDE response.
Entering a value from 1 to 255 into CVs 2.509 and 2.510 will adjust the DDE attack and release time constants from minimum (fastest) to maximum (slowest). Entering a value of 0 into CVs 2.509 and 2.510 will set both DDE time constants to an “instant” response.
JE: Use caution setting a value of 0 in these CVs. The higher the value, the slower the response.
Adjusting DDE Sensitivity Levels
CV 2.511 (DDE Throttle Sensitivity) is used to adjust the correlation between the throttle setting and the exhaust chuff sound effect. Simply put, when the throttle setting is much greater than the current locomotive speed, the load is very high. Conversely, when the throttle is much less than the current locomotive speed, the load is very low. As such, the DDE processor modifies the timbre and volume of sound effects in response to the throttle only when acceleration and deceleration rates are set in CV 3 (Baseline Acceleration Rate) and CV 4 (Baseline Deceleration Rate). You may enter a value from 0 to 255 into CV 2.511 to adjust the DDE throttle sensitivity level. Entering a value of 0 into CV 2.511 will disable DDE throttle sensing.
Setting CV 2.511 to 255 indicates that the cadence and volume of the exhaust chuff sound effect will be most sensitive to the changes in throttle setting.
CV 2.512 (DDE Load Sensitivity) is used to adjust the correlation between motor load and exhaust chuff sound effects. As the motor is impeded during operation, the DDE processor will adjust the timbre and volume of exhaust chuff and rod clank sound effects according to the value of CV 2.512. You may enter a value from 0 to 255 into CV 2.512 to adjust the DDE load sensitivity level. Entering a value of 0 into CV 2.512 will disable DDE load sensing and sound effects will not be modified when the motor is impeded. Setting CV 2.512 to 255 indicates that the exhaust chuff sound effect will be most sensitive to changes in motor load.
Take care to not make the DDE overly sensitive, especially to the motor load signal. Doing so may result in “saturation” of the DDE effect whereby the DDE will simply appear to be unresponsive. This is because even a slight load signal can be amplified to a point that sends the DDE to the extreme end of its settings and thus any additional increase in motor load will have no further effect on the sound.
Note: DDE Load Sensing is disabled if back-EMF is disabled in CV 217.
JE: It is apparent the DDE uses the BEMF signal for the source of change in the loads. Be careful with BEMF reductions.
I find good response with CV212 set to a value above 200. Below that the intensity may not trigger the DDE effectively.
I currently am using CV212 = 255 (100%) and CV10 = 0 which sets no reduction to CV212 giving me the maximum BEMF available for the DDE.