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I've been asked quite often how to adjust the relative volume levels of any manually operated sounds on ZIMO decoders.

There is a simple way to achieve this with CV changes.

You do not need to know how the project author has programmed the sounds. This will work with any project.

With ZIMO, all you need to know is which F key operates the sound you wish to adjust and refer to the list below to obtain the relevant CV number.

The value range is 1 - 255, higher values give greater volume. 0 and 255 both give maximum.

I've also added a list of values equivalent to a range of attenuated (reduced from maximim) levels which you can use as a guide.

If you make these changes using POM, you can hear the changed volume immediately.

F0 CV571
F1 CV514
F2 CV517
F3 CV520
F4 CV523
F5 CV526
F6 CV529
F7 CV532
F8 CV535
F9 CV538
F10 CV541
F11 CV544
F12 CV547
F13 CV550
F14 CV553
F15 CV556
F16 CV559
F17 CV562
F18 CV565
F19 CV568
F20 CV674
F21 CV677
F22 CV680
F23 CV683
F24 CV686
F25 CV689
F26 CV692
F27 CV695
F28 CV698

Here are the fixed sound assignments. The CVs listed control the volume of the sounds shown (if they form part of the sound project loaded):

Boiler Hiss CV574
Direction Change Sound CV576
Brake Squeal CV578
Thyristor Sound CV580
Start Whistle CV582
Cylinder Drain Cock CV584
Electric Motor CV586
Gear Change Sound CV590
Thyristor 2 CV592
Turbocharger CV600
Dynamic Brake sounds CV602

And the external trigger switches:

Switch 1 CV739
Switch 2 CV741
Switch 3 CV743

And the sound from the Random Generators:

Random sound 1 CV745
Random sound 2 CV748
Random sound 3 CV751
Random sound 4 CV754
Random sound 5 CV757
Random sound 6 CV760
Random sound 7 CV763
Random sound 8 CV766

Sound allocation to External Switches and Random Generators is largely at the whim of the sound author, so a little trial and error will be required to find which ones have sound assigned.

When including sounds in the Random Generator it is normal to assign any compressor or air pump sound to Random Generator 1, since this is designed to operate soon after the loco is brought to a halt. (Of course, the sound author needs to have known this and implemented it within the project).

If there is a sound assigned to these F keys, automatic sounds, switches or random generators the volume of that individual sound may be varied, in isolation, by changing the value in the respective CVs shown.

Value range is 1 - 255. (0 is equivalent to 255)

As an aid, here are the values equivalent to a range of sound levels:

Value Attenuation

1 > -27dB Minimum Volume
11 -27dB
16 -24dB
23 -21dB
32 -18dB
46 -15dB
64 -12dB
91 -9dB
128 -6dB
181 -3dB
0 or 255 -0dB Maximum Volume

Kind regards,


Chief cook & bottle washer
2,998 Posts
The F is Function key (The buttons on your controller). If the overall sound has gone quiet, make sure that F27 is off and then press F28. F27 lowers the volume in real time and F28 raises it. If you can do it with your controller, set these two keys to momentary rather then latching. If this doesn't work use CV266 to raise or lower the volume. Read it's value first and then add to it in small (say 10 steps) until you get to where you want. I probably wouldn't go much more than 75 or 80.
Having said all that, it could be that your speaker is failing or failed.
Have a look here at the manual:

Chief cook & bottle washer
2,998 Posts
I've just realised that I didn't remember to ask how old your decoder is. If it's an older version it'll need updating.
Go to CV 396 and enter 27 then go to CV 397 and enter 28. You can also go the CV 395 to determine the maximum volume that you can achieve with F28, bearing in mind that that will never be more than what CV266 is set to. Another one if the version is high enough is a brake Funtion key. Find an unused F key (for instance F22) and go to CV309. Enter 22 (if that's the key you've chosen, just make sure it's unused). Then go to CV349 and enter 5 or 6. this gives the braking force I can't remember what version it needs to be use these CV's but if they don't work it's obviously too old a version.
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