ESU LokSound AutoTune

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Summary: The ESU LokSound 5 / LokSound 5 DCC multi-function sound decoder has a feature called Auto Tune. Some older LokSound V4.0 decoders may also support this feature. Auto Tune allows for automatic calibration of the motor control parameters, such as the BEMF, without editing CVs. It can complete this task more accurately than manually attempting to set the appropriate CVs.


See the Video.

Read your manuals to determine if the feature exists in other decoders by ESU, such as the LokSound 4. This feature may be absent from economy OEM versions.

Auto Tune

The LokSound 5 software controlling the motor operation has been further refined. The Pulse Width Modulation frequency ranges from 10 to 50 kHz for silent operation, with a benefit particularly for coreless motors.

The Load Control has 10 CVs to tune it. The Auto Tune feature allows all ten to be adjusted by the decoder software, perfectly matching the motor performance.

How Does the LokSound Auto Tune Work?

Before beginning, reading and recording the contents of CVs 51 to 56 is advised. This is easiest with the LokProgrammer, or using JMRI's DecoderPro.

For best results, the locomotive should have some running time on the mechanism. A locomotive with a broken in drivetrain will perform better. Run the locomotive for a few minutes before bringing it into position on the track section to be used.

Running Auto Tune

For effective calibration, a length of straight track at least 1.3m long is recommended.

  1. Set CV 54 to the value of 0 (zero) (Load Control Parameter "K")
  2. Leave programming mode
  3. Press F1
  4. The locomotive should begin travelling down the track: It will launch at full speed in the last direction of travel, so ensure it will go the right direction before beginning the process.
    1. At the completion of the Auto Tune process, the locomotive will stop and ring the bell. This should be completed within 1 metre of travel.
    2. Press F1 to silence the bell.

The Auto Tune process will make changes to CV53 (Control Reference Voltage).


After the Auto Tune process has completed, verify operation by taking the locomotive on a test run. If further adjustment is needed, set CV53 (Control Reference Voltage) to a value of 120, and increment or decrement that value as needed.

CVs Referenced

ESU LokSound CVs for Speed Control
CV Name Desciption Default Range
2 Start voltage Sets the minimum speed of the engine 3 0-255
3 Acceleration This value multiplied by 0.25 is the time from stop to maximum speed. For LokSound 5 DCC: This value is 0.896 seconds. 28
4 Deceleration This value multiplied by 0.25 is the time from maximum speed to stop. For LokSound 5 DCC: This value is 0.896 seconds. 21
5 Maximum speed Maximum speed of the engine 255
6 Medium speed Medium speed of the engine. Used only if the 3-point speed table is enabled. LokSound 5 DCC only.
49 Extended Configuration #1 See Loksound documentation for full details 19 0-255
51 "K Slow" Cutoff Internal Speedstep, until "K Slow" is active 1
52 BEMF Parameter "K Slow" K Portion of the PI-Controller valid for lower speed steps 0
53 Control Reference Voltage Defines Back EMF voltage, which the motor should generate at maximum speed. The higher the efficiency of the motor, the higher this value may be set.

If the engine does not reach maximum speed, reduce this value.

54 Load control Parameter "K" K component of the internal PI-controller. Defines the effect of load control. The higher the value, the stronger the effect of Back EMF control. 50
55 Load control Parameter "I" I component of the internal PI-controller. Defines the momentum (inertia) of the motor.

The higher the momentum of the motor (large flywheel or bigger motor), the lower this value has to be set.


Known Problems

Some locomotives with factory (OEM) multifunction decoders installed may not work correctly with AutoTune. Rapido Trains' RDC and Royal Hudson may not tune correctly due to their custom programming.

Royal Hudson by Rapido

These locomotives and their ESU Multifunction Decoders require a different reset procedure as setting CV8 to "8" will not change the necessary CVs on the ESU LokSound Version 5 decoder. To reset this model to its original factory settings, follow this two-step procedure:

Step 1

  • Select the locomotive address you are currently using. If you did not program a custom address, the default is "3".
  • In programming mode, change CV8 = 8
  • Cycle power. This may require leaving programming mode and energizing the decoder, then disconnecting power or removing the locomotive from the track.

Step 2

  • Select address "3"
  • Change the values of these CVs in the order listed below:
  1. CV51 = 1
  2. CV52 = 0
  3. CV53 = 120
  4. CV54 = 50
  5. CV55 = 100
  • Cycle power.

Your model is now reset to factory defaults and will respond to address "3" until a custom address has been programmed.

  1. Changes can be made with most DCC systems, an ESU LokProgrammer or JMRI.
  2. Some DCC systems may not provide adequate current to reprogram an ESU decoder. If this happens, you will need to use a DCC Programming Booster.
  3. Use caution during programming, make sure it is isolated and that no other locomotives sharing the same address are active.

ESU Tech Tip

Short video demonstration of AutoTune.

Adjusting Speed Parameters

Adapted from a message posted on the LokSound email list.[1][2]

The names of CVs in this post are those found in the LokProgrammer software, not necessarily the names defined by the NMRA.

The best results can be achieved by:

  • Disabling CV124.4, "Adaptive Regulation Frequency,"
  • Setting CV10, "Back EMF Sampling Period" to its largest value of 8.
  • CV49.1, "DC Motor PWM Frequency" set to 40 KHz.
  • CV56, "Regulation influence" was left at maximum, or 255.

Low speed

Try manually setting CV51 "I slow" to 0, and CV52 to a small value, smaller than auto-tune recommends. Perhaps half or less.

Any non zero value in CV51 may cause locomotives to surge.

For higher speed steps, if either CV54 "K" or CV55 "I" is too large the locomotive will surge.

To manually tune, set CV55 to a small value, perhaps 10 or less, then set CV54. If CV 54 is too large, the locomotive will surge. If too small, the locomotive slows down too much as the load increases, such as when running through the curved leg of a turnout. When satisfied with CV54, then CV55 can be increased a little bit until surging re-appears, then back off 10-25%.

Adjusting Top Speed

Finer control and improved low-speed performance can be achieved by reducing CV5, "Maximum speed" so that the engine runs no faster than desired.

Alternatively, CV53, "Regulation Reference" may be reduced. This is the Back EMF produced at full speed.

Next adjust CV2, "Minimum Speed" for the desired starting speed in step 1.

Some momentum is necessary when running in 28 speed step mode to make a smooth speed changes when adjusting the throttle, even when by only one step. With considerable momentum, the sound schedules will produce far more prototypical behavior.

Further Reading