Digitrax SoundFX SDXH186MT User manual

© 2017 Digitrax, Inc. www.digitrax.com— 1 —
Complete Train Control
Run Your Trains, Not Your Track!
Features:
▪Digitrax SoundFX®Sound System
Your locomotives will sound in scale like the real thing with SoundFX
Customizable 16, 12 or 8 Bit Sound
Works with SoundFX 8 and 16 Bit sound projects
4 Simultaneous voices
Downloadable Sound with Digitrax PR3 and SoundLoader 2.0 software
16 Megabit On board Sound Memory
1 Watt Sound Output
Cam input-synchronized steam-chu option for steam locos
Scaleable Speed Stabilization(BEMF) optimized for sound operation
▪Congurable Logic Level or 12v F3-6 function outputs.
▪SoundFX does not require an external rate sensor to vary workload.
▪Smart Power Management-no more booster or programmer shutdowns!
▪Program CVs using any Digitrax Compatible Control system without having
to buy any extra equipment.
▪Compatible with Locomotives using the 21MTC Interface
▪Series 6 Decoder Features.
▪Works with PX112-10 Power Extender.
▪Digitrax FX3Functions-Control lights and functions for prototypical lighting
eects and on/o control.
▪Congurable FX3Pulse Function available on all function outputs.
▪Digitrax LocoMotion®System – Lets your trains run like the real thing!
▪2 Digit and 4 Digit Addressing.
▪Basic, Advanced & UniVersal Consisting.
▪SuperSonic motor drive for silent operation.
▪Direct mode programming.
▪Decoder Reset CV with or without speed table reset.
▪Transponder Equipped ready for transponding on your Layout.
▪Motor Isolation Protection helps prevent damage to your decoder.
▪DCC Compatible.
▪FCC Part 15, Class B RFI compliant.
▪Digitrax “No Worries” Warranty.
SDXH186MT SoundFX®
Fits many HO locomotives
8 Selectable Steam & Diesel Sound
Schemes Included
1.15”x.64”x.21”
29.28mm x 16.26mm x 5.34mm
HO Scale
Mobile Decoder with SoundFX
21MTC interface
1.0 Amp/2 Amps Peak
8 FX3Functions, 200ma output

© 2017 Digitrax, Inc. www.digitrax.com— 2 —
Parts List
1 SDXH186MT Function Decoder with SoundFX®
1 Instruction Sheet
Installation Information
See the Digitrax Decoder Manual for complete decoder test procedures, instal-
lation instructions, programming and technical information. Digitrax manuals
and instructions are updated periodically. Please visit www.digitrax.com for the
latest versions, technical updates and additional locomotive-specic installation
instructions. CAUTION: Programming and layout track must not exceed
16V when using this decoder.
Installation Instructions
1. Carefully remove the locomo-
tive shell. (Figure 1) Note
the orientation to the frame
for correct re-installation.
Arrange internal wires to
expose the jumper board in the
locomotive.
2. Remove the jumper board
from the locomotive’s 21MTC
pins. (Figure 2) The jumper
board allows the loco to op-
erate on a standard DC track
or in analog mode on a DCC
track. If the loco also has
a 8pin NMRA socket, any
jumpers should also be
removed.
3. Insert the 21MTC socket onto
the exposed pins. The black
socket and the decoder text
should be facing up. The
socket is indexed so it will only
t on in one conguration.
(Figure 3) Seat the decoder
rmly on the pins.
Figure 1: Remove loco shell
Figure 2: Carefully
remove jumper board
Figure 3:
Carefully plug in decoder. Shown with op-
tional SP2615BC speaker.

© 2017 Digitrax, Inc. www.digitrax.com— 3 —
Note: The SDH186MT does not include a speaker. This install is shown with an
optional SP26158BC. Please refer to you locomotive manufacturer for the best
way to attach a speaker to you locomotive motherboard.
4. Inspect the installation before testing the sounds and replacing the shell. In
particular be sure that wires are correctly routed and not pinched between
the shell and frame.
5. Place the loco on an active DCC track powered by a compatible DCC system
and select the factory default address 03 to enable sounds for testing.
6. Be sure F8 (mute) is OFF to allow sound output, and then press
F1 (bell) or F2 (whistle/horn) ON to hear the associated sounds.
7. Customize sounds by programming Sound CVs to adjust the desired cong-
urations, as shown in the following tables of SoundFX CVs. Sound schemes
other than the 8 factory preloaded can be loaded by using a Digitrax PR3
SoundFX Programmer or DCS240.
Speaker Mounting and bae or enclosures.
The sound performance of any attached speaker(s) is greatly aected by
the mounting system and required bae or rear enclosure. The includ-
ed 8ohm box speaker is pre-mounted in a bae for your convenience,
however additional baes or other mounting systems may need to be
taken into consideration when installing. The bae is used to isolate the
speaker diaphragm front sound waves from the “out of phase” rear sound
waves. This minimizes sound cancellation, particularly at lower frequen-
cies. For most ecient sound generation, the cubic volume of the bae
should be as large as practically possible, and the bae walls should be
acoustically rigid so not to allow acoustic interference.
Practical bae materials are plastic, cardboard and even sheet metal.
Common items such as cardboard tubes, soda caps, or 35mm lm can-
isters may be modied and trimmed to create reasonable baes in the
available space. Most HO or O scale or similar locomotives have limit-
ed internal volume within the shell, so the choice of speaker mounting
benets from some ingenuity to get best sound performance and space.
Of course, you can substitute an alternate after market speaker of the
maximum size for the locomotive you have.

© 2017 Digitrax, Inc. www.digitrax.com— 4 —
Customizing Your Decoder
Your Digitrax SDXH186MT SoundFX decoder is ready to run and will
operate and generate sound (with an installed speaker) using address 03
with no additional programming. On your Digitrax system, simply select
the locomotive’s address and the sound will start. On some DCC systems,
it is necessary to select the locomotive address AND send a command to
start the sounds.
For a more prototypical railroading experience, your decoder can be
customized for your specic locomotive by programming some of the
Conguration Variables, or CVs, available. Digitrax Sound decoders can
be programmed using either a programming track or with the operations
mode using the main line. See the Digitrax Decoder Manual or the Digi-
trax web site for more information.
CAUTION: Programming track must not exceed 16V when
programming this decoder.
Initial Test and Programming: This decoder is preprogrammed and
tested with a diesel locomotive sound scheme, and is ready to operate on
factory default address 03. Before customizing the decoder it is useful
to run it on the factory default address 03 to check the installation. The
following sections show how to change the locomotive address and cus-
tomize the decoder.
For more information on general decoder installation and programming
techniques and examples visit www.digitrax.com
Changing the Decoder Address
The rst CV most people change is the decoder address. This allows
you to independently control each loco with a unique address. Digitrax
decoders are shipped with CV01 (AD2), the two digit address, set to 03.
Following is a brief description of how to change the decoder address
with a Digitrax DT4XX series throttle. See your Starter Set Manual for
complete programming instructions.
1. Place the loco on the programming track not to exceed 16V.
Go into Program Mode on your system. On DT4XX throttle press
PROG.

© 2017 Digitrax, Inc. www.digitrax.com— 5 —
2. Choose AD2 for 2 digit addressing or AD4 for 4 digit addressing.
3. Choose the address you want to set up for the decoder.
4. Complete address programming by pressing ENTER.
Note: CV29 must also be programmed to enable 4 digit addressing, this
is done automatically by the DT4XX throttles. See your Digitrax Decoder
Manual or the Digitrax Toolbox App for how to set up CV29.
Using this decoder in other locomotives
The factory supplied sound project loaded into the SDXH186MT is for a
GP38 diesel locomotive, other preloaded projects are selectable with the
value in CV60. If you want to install it in a dierent locomotive, you can
simply load a dierent sound project for that type of locomotive. The cam
input is available on pin 1 for Steam installations where supported by the
locomotive.
Digitrax LocoMotion®System
Your locomotives look like the real thing, now you can make them run
like the real thing, too. Digitrax decoders incorporate torque compensa-
tion for smooth as silk operation. You can also program CVs that control
momentum, 3 step and 128 step speed tables, switching speed, normal
direction of travel, scalable speed stabilization and more to take full ad-
vantage of the Digitrax LocoMotion System.
Momentum-CV03 & CV04
Momentum is part of the LocoMotion System. Acceleration is controlled
by CV03 and deceleration by CV04. Both come from the factory set to
000. A range of 000 to 031 is available for both accel and decel. Try
CV03:003 and CV04:000 as a starting point for experimenting with
momentum.

© 2017 Digitrax, Inc. www.digitrax.com— 6 —
Speed Tables-How the Loco Responds to the Throttle
With Digitrax LocoMotion, there are two types of speed tables: 3 Step Ta-
bles and High Resolution 28 Step Tables. Please see your Decoder Man-
ual for a discussion of the 28 Step Tables. The 3 Step Tables are set up
by programming 3 CVs: Start Voltage (CV02), Mid point Voltage (CV06)
and Max Voltage (CV05). These values are set at 000 at the factory. All
have a range of values from 000 to 255. We recommend the following CV
values as a starting point for experimenting with speed tables.
Loco Type V Start
CV02
V Mid
CV06
V Max
CV05
Switcher
Concentrated low speed. Limited top
speed
002 038 064
Road Switcher
Prototypical top speed w/evenly
distributed curve from 0 to top speed
002 048 098
Mainline Loco
Quick increase to cruising speed then
levels o to prototypical top speed.
002 128 154
Decoder Reset CV08
Decoder reset lets you reset all CV values to the initial factory settings. To
reset all CV values, program CV08 to a value of 008. You also have the
option of resetting all values except the 28 speed step tables. To do this,
program CV08 to a value of 009.
Other LocoMotion®Features: Switching Speed, Normal
Direction of Travel & Scalable Speed Stabilization
(Back EMF) Features
Switching speed is controlled by CV54. The factory setting is 000 for
OFF. To turn on the switching speed feature, program CV54 to a value of
001. When this feature is on, use F6 to activate and deactivate switching
speed. With the feature on the throttle’s target speed is eectively re-
duced by about 50% and the eects of accel and decel programmed into
the decoder are reduced by 1/4. This is useful for yard switching opera-
tions.
Normal Direction of Travel is controlled by CV29. See your decoder
manual or the Digitrax Toolbox App for additional information on the
settings for CV29.

© 2017 Digitrax, Inc. www.digitrax.com— 7 —
Scaleable Speed Stabilization (Back EMF) intensity, or droop, is
controlled by CV57. The factory setting for this feature is 006 which is
suitable for most locos. You can adjust this value in the range of 000
for OFF to 015 for the maximum eect. Consult your Digitrax Decoder
Manual for info about CVs 55 & 56 and their eects on scaleable speed
stabilization. The factory setting for both CV55 & CV56 is 000.
Logic Level or 12v 21 pin function outputs CV64
The DH166MT can be congured via CV64 for compatibility with either
Logic Level or 12 Volt function formats for outputs F3,F4,F5, and F6. By
default CV64 is set to a value of 0 for Logic Level compatibility. This is
the most common conguration for locomotives using the 21MTC inter-
face. Setting CV64 to a value of 64 will set a bit for function compatibility
to 12v format comparable to that of F0, F1, and F2 .
Digitrax SoundFX®System
Digitrax SoundFX lets you make your locos sound in scale like the real
thing! The SoundFX sound CVs in the range of CV140 to CV256 let you
customize your decoder without having to reprogram or change the in-
stalled sound scheme.
Diesel Notching CV132 and 155
Sound CV155 is provided to select Diesel engine “notching” modes. The
default of CV155= 00 provides “automatic notching” that changes the
diesel RPM settings at 8 distinct throttle speeds that are controlled by
Sound CV132. Sound CV155=01 selects “semi-automatic notching” mode
that allows F6 ON to increase the notch from the current throttle setting
and F7 ON to decrease back towards the lowest current throttle notch
setting. Sound CV155=02 selects “manual notching” mode that allows F6
ON to increase the notch setting and F7 ON to decrease the notch setting
irrespective of the throttle setting, which controls just the motor speed.
Steam Chu / Cam Conguration and Gear Rotation
Trim CV133 and 134
CV133 controls the Steam Chu / Cam conguration in the decoder it
allows you to get the value of the CV equal to the diameter of the driver in
inches from 1-27 or to set the CV to 128 to enable the external cam lead.
CV134 controls the gear rotation trim where a value of 32 equals a 100%
ratio.

© 2017 Digitrax, Inc. www.digitrax.com— 8 —
Bell and Air Eect Rates CV146-149
CV146 controls the bell rate or time between ring of the bell, it has a
range from 1-100 with each increment adding 24ms of delay. CV147 con-
trols the drier rate, it has a rage from 1-64 with each increment adding
about 2 seconds. CV148 controls the Compressor/ Air pump start rate
and CV149 controls how long the Compressor/ Air Pump runs.
Auto Coupler Sequence Threshold Value CV151
CV151 controls the threshold at which coupler and brake sounds are
automatically played when locomotive direction is changed and function
3 is enabled. CV151 has a range of 0-60.
Changing the Sound Scheme on your SDHX166D CV60,
150, 157
The SDHX166D comes preloaded with 8 dierent sound schemes, 6 die-
sel and 2 Steam. These schemes can be selected using CV60. Each diesel
scheme can be congured with one of 8 dierent horns using CV150 and
one of 4 dierent bells using CV157. Each Steam scheme can be cong-
ured with one of 3 whistles using CV150 and one of 4 bells using CV157.
To enable playable volume for your selected horn or whistle add 128 to
the selected value (ex. Playable volume on horn 2 is enabled with a value
of 130, 02+128=130)

© 2017 Digitrax, Inc. www.digitrax.com— 9 —
CV60
set to Sound Scheme CV150 set to CV157 set to
0 GP38 Diesel
0= default 1-7= alt
horns
128-135 = Playable
horns
0=default 1-3 = alt
bells
1GE Evolution
Diesel
1= default 0-7= alt
horns
128-135 = Playable
horns
0=default 1-3 = alt
bells
2 SD70 Diesel
2= default 0-7= alt
horns
128-135 = Playable
horns
0=default 1-3 = alt
bells
3 GP10 Diesel
3= default 0-7= alt
horns
128-135 = Playable
horns
0=default 1-3 = alt
bells
4 RS1 Diesel
4= default 0-7= alt
horns
128-135 = Playable
horns
0=default 1-3 = alt
bells
5 C420 Diesel
5= default 0-7= alt
horns
128-135 = Playable
horns
0=default 1-3 = alt
bells
6Steam type 1
(based on 3985)
0= default 0-2= alt
whistles
128-130 = Playable
whistles
0=default 1-3 = alt
bells
7Steam type 2
(based on K27)
1= default 0-2= alt
whistles
128-130 = Playable
whistles
0=default 1-3 = alt
bells
Loading Other Sound Schemes in your SDHX166D
The decoder’s sound scheme can be changed using a Digitrax PR3 pro-
grammer and your computer with the SoundLoader 2.0 software. Both
the software and a number of alternate sound project les are available
from the Digitrax Sound Depot web site. It takes only a few minutes to
download the new sound to your decoder. The following tables show the
CVs used in this decoder version and how it is set up at the factory to
operate various sounds using your throttle. (Table on next page.)

© 2017 Digitrax, Inc. www.digitrax.com— 10 —
CV# Used For Range Default
Value
01 2 Digit Address 03
11 Sound Time Out, 06 = Sound ends when loco address is
de-selected, 00=Sound stays on after loco is de-selected 06
29
Conguration Register - Advanced or Standard speed steps,
2 or 4 digit addressing, Analog Mode, Normal direction of
travel, speed tables
06
49 Forward Light (FOF) - Headlight 00
50 Reverse Light (FOR) - Reverse Light 00
51 Function 1 00
52 Function 2 00
58 Master Volume (F8 used for Mute) 1=min 00=max 00-15 09
60 Sound Scheme Select 00-07 00
132 Notch Rate 00-255 127
133 Steam Chu/CAM cong, 128=>EXT cam, 1-127=>DRIVER
dia in inches 01-128 63
134 Steam Gear Ration Trim, 32 = 100% Ratio 00-255 32
135 Mute Volume 00-64 00
140 Prime Mover / Chu Volume 00-64 60
141 Bell Volume 00-64 25
142 Horn/Whistle Volume 00-64 60
143 Time-Scattered Air Eects Volume 00-64 30
145 Misc Vols 00-64 40
146 Bell Ring Rate (1=24 milliseconds) 01-100 07
147 Air Drier Rate (1-about 2 seconds) 01-64 02
148 Compressor Run Rate 00-255 30
149 Air Compress On Time 00-255 20
150 Horn/Whistle Setup (Default=0, Playable Horn=1, Alter-
nate Horn=2 +128 for playable volume.)
00-07
or 128-
135
00
151
Auto Coupler Sequence Threshold Value-Peak speed to
allow auto coupler/brake when direction change occurs and
F3 is ON
00-64 48
152 Project Author ID, Digitrax=221 221
153 Project ID 168
154 Steam Blow down / Safety Volume 0-64 60
155 Notching/Slip Mode: 00=Automatic, 00
157 Bell Selector 00-03 00

© 2017 Digitrax, Inc. www.digitrax.com— 11 —
Function Used For Notes
F0 Lights
F1 Bell
F2 Horn/Whistle CV150 sets mode
F3 Coupler crash Auto coupler/brake set by
CV151 max speed
F4 Air feature disable
F4 o enables pop-o,
drier and starts compres-
sor/airpump
F5
Diesel = Dynamic brake
Fans Steam = Water
Pump turbine
F6 Diesel = Notch Up
Steam = Blowdown
Notch UP if CV155=01 or
02
F7
Crossing Gate Airhorn
or;
Diesel = Notch DOWN
Steam = Wheelslip
Notch DOWN, if
CV155 = 01 or 02
(Crossing Gate active if in
Diesel mode and CV155=0)
F8 Mute Control F8 ON is mute
F9 Brake squeal
F10 Crossing Gate
Airhorn Sequence
F11 Steam = Greaser
F12 Steam = Safety Blowo
SoundFX DC Operation Mode
Digitrax SoundFX decoders will operate on smooth DC power. The sound
will not start until approximately 7 volts is applied to the track and there
will be no “start up sound.”

© 2017 Digitrax, Inc. www.digitrax.com— 12 —
SDXH186MT Troubleshooting
If the sound does not start in the decoder
1. Make sure you have selected the locomotive address on a throttle.
The sound will not run unless the locomotive is addressed in the
system.
2. Check your installation to make sure the decoder is installed
properly.
If the sound output sounds distorted
1. Check the speaker cone for magnetic debris that may have collected
there. Debris on the speaker will cause a loss of sound quality and
must be removed.
2. Be sure that the CV58 volume is not set at a level that is too high for
the speaker being used.
If the sound in your decoder shuts down after you stop it and
you are not using a Digitrax system for control. On some DCC
systems decoders are not addressed by DCC packets after the locomotive
is set to 0 speed. In this case after the CV11 timeout elapses (6 second
default), sound will “shutdown.”. To defeat this feature, set CV11=00 to
remove the timeout and shutdown. To make sounds, the decoder must
have a command addressed to it at least once.
If you have trouble reading back CVs on the programming
track, this may be due to insucient current draw. Of course you can
always just re-program the CV value into a CV to get the desired results,
even if reading CVs does not work. OPS mode is recommended for writ-
ing to (programming) all CVs except CV01, CV17 & CV18 (2 digit and 4
digit addresses). If a second DCC decoder is present that is not SoundFX
compatible then correct read back of CV data is not possible, since the
NMRA CV read back was not designed for multiple decoder read back.
The SDXH186MT plays a Steam scheme, but I want the default
Diesel scheme. If the factory scheme has not been erased, program
CV60 to a value of 0 to reselect the default GP38 diesel scheme.

© 2017 Digitrax, Inc. www.digitrax.com— 13 —
I have loaded a new scheme but the CVs and Functions are not
what I expected. Load the sound project you programmed and then se-
lect the view>project description” menu and then read the text le on the
screen that denes how that project in particular uses CVs and functions
for sound generation and conguration.
Warranty & Repair
Digitrax gives a one year “No Worries” Warranty against manufactur-
ing defects and accidental customer damage on all Digitrax command
stations, boosters, throttles, decoders, power supplies and layout control
devices.
That’s it! A simple, straightforward warranty with no tricky
language!
Visit www.digitrax.com for complete warranty details and instructions
for returning items for repair.
Please return warranty items directly to Digitrax - DO NOT re-
turn items to place of purchase.

© 2017 Digitrax, Inc. www.digitrax.com— 14 —
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TM
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Made in the USA
2443 Transmitter Road
Panama City, FL 32404
www.digitrax.com
Need Support?
helpdesk.digitrax.com
SDXH186MT
Fits Many HO Locomotives with 21MTC interface
307-9003-0000