Fitting the DRS Bachmann Class 57/0 locomotive pair with Bif. LokSound V4. Decoders.



The sound quality and driving technique of the Legomanbiffo (Bif.) sound equipped Network Rail 57/3 was sufficiently impressive to prompt a switch to the same LokSound V4 fit on my two DRS Class 57s, used on the MOD nuclear train. The main changes required are due to the much less flexible function output arrangements of the ESU LokSound, when compared to the Zimo decoders. However, with fairly simple lighting arrangements on the Class 57/0, it is not necessary to provide an additional function decoder. Instead, discrete component buffer amplifiers will be fitted to enable the LokSound Aux 3 & 4 logic level function outputs to be used without recourse to the ESU adapter board, which is almost certainly too big for this application.

Class 57/0 at York station in 2008.


The Planned lighting controls:

Because the locomotives are used double headed within the train and occasionally in double headed light engine configuration, independent control of the (directional) lights at each end of the locomotives is a requirement. The following arrangement is therefore proposed:    (FO = "function output")

(1) Directional lights at end one, activated by button zero. (Headlight FO to end 1 forward lights and rearlight FO to end 1 rear lights).

(2) Directional lights at end two activated by button 14. (Aux1 FO to end 2 forward lights and Aux2 FO to end 2 rear lights).

(3) End 1 driver's cab light activated by button 11 (Aux4 FO plus buffer amp).

(4) On lead loco 57011 only: Detonator flash LED activated by button 17 (Aux3 via buffer amp).

(5) On rear loco 57012 only: Connector feed at end 2 to enable some (dubious) effects in the front nuclear flask carrier, enabled via button 20 (Aux3 via buffer amp).



Revised Class 57/0 Interconnect:

The original Bachmann yellow marker light LEDs have been replaced with new pure white types to represent the real loco's current LED technology marker lights.


Alternative discrete buffer amp circuits: (Depending on which bits I have available when the decoders arrive.)

The N-channel MOSFET solution uses just a single surface mount (SOT23) size component per FO, which is small enough to fit on the main PCB, but just large enough for hand soldering with thin wires.

The NPN transistor circuit is believed to be similar to those on the ESU adapter board.


In both circuits, the load (which must include a suitable series resistor) is connected between the buffered output and common positive. The Aux3 and Aux4 decoder outputs are believed to be at ground voltage when off and at +5V (wrt ground) when active. They have very limited current handling performance.  (The MOSFET solution was finally chosen.)


Programming the Decoder:


Action CV Orig value Final Value
Master Volume adjustment


192 70


Function Mapping:

Function Button Mapping line Original Assignments Sound Slot Original Volume New Button Assignments (change areas in blue)
0(Fwd) 5 headlight FO     (with direction Fwd+F0 on): headlight FO (=End 1 H/L & fwd mkr lights)
0(Bwd) 6 rearlight FO     (with direction Rev+F0 on): rearlight FO (= End 1 rear lights)
1 7 Engine prime/start/stop 1 & 2 128 & 60 Engine prime/start/stop
2 8 Playable High Note Horn 23 128 Playable High Note Horn
3 9 Playable Low Note Horn 24 128 Playable Low Note Horn
4 10 Buffer Clash 4 100 Buffer Clash
5 11 Air Release 5 70 Air Release
6 12 Drivers door slam 6 110 Drivers door slam
7 13 Compressor 7 90 Compressor
8 14 Spirax Valve Popping 8 40 Spirax Valve Popping
9 15 Flange/Wheel Squeal 9 128 Flange/Wheel Squeal
10 16 Dispatch Whistle 10 50 Despatch Whistle
11 17       Aux4 FO: (=Cab light)
12 18 Roof Fan/Cooler Group 12 120 Roof Fan/Cooler Group
13 19 Sanders 13 60 Sanders
14 20       (Make with direction Fwd+F14 on): Aux2 FO (= End 2 rear lights)
14 21       (Make with direction Rev+F14 on): Aux1 FO (=End 2 H/L & fwd mkr lights)
16 22        
17 23       (Make with direction Fwd+F17 on): Aux3 FO (=detonator flash Loco1 only)
18 24 Detonators 18   Detonators
19 25 Aux 1 FO     Remove Aux 1, add Zero Momentum Mode
20 26 Aux 2 FO     Remove Aux 2 (Make with F20 on): Aux3 FO (=connector feed Loco2 only)


Action Index CV32 CV Change Detail
CVK for line 17 0 to 32


3/266 from 0 to 32

Line 20 CVA 0 to 4; CVK 0 to 8 3 3/305 from 0 to 4;   3/314 from 0 to 8
Line 21 CVA 0 to 8; CVE 4 to 1; CVK 0 to 4 3 3/321 from 0 to 8;   3/325 from 4 to 1;   3/330 from 0 to 4
Line 23 CVA 0 to 4; CVK 0 to 16 [Loco 1 only] 3 3/353 from 0 to 4;   3/362 from 0 to 16
Line 25 CVK 4 to 0; CVM 0 to 1 3 3/394 from 4 to 0;   3/396 from 0 to 1
Line 26 CVK 8 to 0; [Loco2 only: CVK 8 to 16] 3 3/410 from 8 to 0;  [Loco 2 only: 3/410 from 8 to 16]




Active Button Sound Slot Assignments (& Lighting Controls): 

Most of the sound slots (at least all of those I've checked) are set at maximum volume, so to make any of them sound louder compared to the diesel engine sounds, I've had to reduce the volume of the engine sounds in sound slot 1.

Sound & Light Control Function list

Sound Slot Volume changes Volume CVs  (CV32=1 first)
F0 End 1 directional running lights -    
F1 Sound On/Off and engine start/stop. 1 & 2 128 to 110 & 60 to 52 259 & 267
F2 Playable High Note Horn. 23    
F3 Playable Low Note Horn. 24    
F4 Buffer Clash/Buffering up when moving slowly. 4    
F5 Air Release (Air Dump). 5    
F6 Drivers door slamming.   6    
F7 Compressor Startup.   7    
F8 Spirax valves.  8    
F9 Flange/Wheel Squeal Enable. 9    
F10 Dispatcher's whistle. 10 50 to 90 331
F11 Driver's Cab Light -    
F12 Roof Fan/Cooler Group 12    
F13 Sanders 13    
F14 End 2 directional running lights -    
F17 Detonator flash. (Loco1 only) -    
F18 Triple Detonators. 18    
F19 Set zero momentum (for test purposes only) -    
F20 Flask flash. (CV 0/291=12; CV112=10) Loco 2 only -    


Motor Control Settings

CV CV Value Description
2 1 Start voltage
3 170 Acceleration delay
4 89 Deceleration delay
5 210 Max. speed setting
6 75 Med. speed setting  (<100 expands slow speed part of range)
49 19 Ext Config.1 includes 40kHz motor pulse frequency
51 2 Slow driving I component
52 40 Slow driving K component
53 85 Max speed adjustment
54 50 Normal driving K component
55 100 Normal driving I component (proportional to motor momentum)
56 255 100% range speed control
124 5  Ext Config.2 includes Enable adaptive regulation frequency

Smooth running is achieved across the entire speed range, but I'm sure many other combinations will achieve the same result!


Detonator flashes:

The Legomanbiffo sound project includes a triple detonator sound sequence. I've fitted a tiny chip LED on the frame of the front bogie near the bottom of the front wheel. The wires are fed up to the main PCB through the same holes as the wheel contact wires. The LED is connected to the Aux3 function output buffer via a 1k resistor. I operate the loco using PC control and I can briefly activate the LED using the Traincontroller software, at the same time as the detonator sounds occur. To see this in action on YouTube, click on the link immediately after the detonator flash photo below.

To watch a You Tube clip showing the detonator flash, click here.


I've also cooked up an electrical circuit that will produce similar results if computer control is not available.  It consists of an astable multivibrator with the "on" time for the LED of around 100mS and off time between flashes of about 1.25 seconds. The astable circuit is held with the LED "off" by the third transistor, until a negative going output is provided by one of the decoder function outputs, which should be activated simultaneously with the detonator sounds.

If you build this circuit, the values of the resistors marked with a star will need fine tuning to get the timing right, as the tolerance of the electrolytic capacitors used, is very wide.  The 680K controls the flash repetition time and the 100k is adjusted to provide just three flashes whenever the detonator flash is activated. The transistors are low power NPN devices with a reasonable gain (eg BC549C). The diodes are there to prevent reverse breakdown of the transistor base-emitter junctions and are ordinary small signal types (e.g. 1n4148). The idea is to modify the function mapping of the LokSound V4 decoder to trigger the function output from the same button that initiates the detonator sound. The button needs to be left "pressed" for at least the duration of the three flashes, before being re-set.



To watch a You Tube clip of the finished 57s with the MOD Flask Train, click here


Adding some useful ESU "logic functions":

Included in the ESU LokSound V4 are several additional features that can be assigned to any available control buttons:

Using the functions section of the comprehensive V4 manual, these steps activate the sound fader and the manual diesel notch control.

1) Volume fader: Fit to button 21:  Set register CV32 to 3 then set CVN=CV429 to 8. Set CV133 to 75 for a little over half volume.

2) Diesel Notch-Up: fit to button 22: Set register CV32 to 3 then set CVN=CV445 to 2.

3) Diesel Notch-Down: fit to button 23: Set register CV32 to 3 then set CVN=CV461 to 4.


Revised Sound & Light Control Function list

F0 End 1 directional running lights
F1 Sound On/Off and engine start/stop.
F2 Playable High Note Horn.
F3 Playable Low Note Horn.
F4 Buffer Clash/Buffering up when moving slowly.
F5 Air Release (Air Dump).
F6 Drivers door slamming.  
F7 Compressor Startup.  
F8 Spirax valves. 
F9 Flange/Wheel Squeal Enable.
F10 Dispatcher's whistle.
F11 Driver's Cab Light
F12 Roof Fan/Cooler Group
F13 Sanders
F14 End 2 directional running lights
F17 Detonator flash. (Loco1 only)
F18 Triple Detonators.
F19 Set zero momentum (for test purposes only)
F20 Flask flash. (CV 0/291=12; CV112=10) Loco 2 only
F21 Volume Fader.
F22 Diesel Notch-Up.
F23 Diesel Notch-Down.


Supplier website links:


Rails of Sheffield    The Class 57 units above were originally purchased from this excellent e-shop.
DC Kits & DE Videos    Helpful source for Legomanbiffo (Bif) LokSound V4 sound decoders & ESU speakers.
ESU website    For access to the V4 user manual.
Rapid Electronics of Colchester    A good reasonably priced source for electronic components.


The photos of the models were taken using a hand held Canon Ixus 220.     The photos of the real 57012 loco were taken back in 2008 at York Station.


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