# Dcc control with analog sound. Is it possible.



## MartyI (Dec 24, 2009)

I have been switching over my lgb collection to my new piko dcc control system. I have a few diesel locos that have sound in them already.. Trying to save a buck on a sound decoder and just go with a regular decoder, I was thinking of a way to keep the original sound board. Here's my thought...
If I completely separate out the old sound board from the motors and lights, and use the new dcc decoder for lights and motor control and just tap in two leads from the motor output of the dcc controller to the old sound board, would this work. The motor output is variable and in theory should change the levels of the sound. Am I way off on this thinking.
Thanks for any insight


----------



## SteveC (Jan 2, 2008)

I'm no expert, but, the DCC voltage that is placed on the track is at a constant level and does not vary with the speed of the locomotive. Additionally, the DCC signal is similar to a PWM (pulse width modulated) signal, and that type of signal has been known to not work well with the older LGB sound modules.


----------



## MartyI (Dec 24, 2009)

The way I would wire it, the voltage would vary, as do the motors. Interesting work-around I think. I may need to try.


----------



## krs (Feb 29, 2008)

Marty - As you said, just try it out. 

Some of the older LGB sound modules will probably work properly and others won't. 
The ones that do not need a filter between the decoder PWM output and the sound module input to change the PWM decoder output to an analogue variable DC voltage for the sound module. 
The filter design needs to be such that it allows enough current to power the LGB sound module. 

Someone once sent me an LGB schematic of that filter, I'll see if I can find it. 
It was basically an LC filter but using values that allowed sufficient current to power the sound unit. 

Knut


----------



## Greg Elmassian (Jan 3, 2008)

you may have to filter the motor output to the decoder, but it is definitely do-able and has been done a number of times. A full wave bridge, filter cap and possibly an inductor will do the trick. Aristo makes a board for this too. 

Greg


----------



## Axel Tillmann (Jan 10, 2008)

I personnaly think this is an attempt to fit a square peg through a round hole.

You engage into DCC to have also all the sounds accessable. Old sounds cannot be triggered by DCC commands. However old soundboards will still fetch >$40 on the market for some DC hobbyists. $40 is about to cover the dfiferential from a regular DCC to an integrated DCC board.

I would think twice (or even ten times) about it.


----------



## Trains West (Oct 4, 2008)

I do this all the time ...... it works just fine 

the sound power comes from the motor output on the dcc board just like you stated 

if you want add a few full wave bridges with the ac legs shorted together inline to the motor but not the sound .... its will let you power the sound with the first click on the throttle but not let the loco move .... that way it sits all day with sound running 

to trigger the bell and horn I put a relay on the fuction output that will complete the "loop" of trigger just like a reed switch 

easy as pie and no need for other sound systems


----------



## Jerrys-RR (Jun 21, 2010)

This is a circuit that worked for me with a MRC decoder in an Aristo-Craft FA-1 or FB-1. I was not happy with the MRC decoders lack of speed compatibility in dual loco use so I ended up running both the FA-1 and FB-1 from one decoder which did work. The MRC decoder did not work under analog track power but the important thing is that the two resistors and capacitors DID work very well in converting my LGB analog sound systems to work both under MTS/DCC and under analog track power.

The sound system circuit was developed by LGB for use with LGB analog sound cars to adapt them to work with MTS. It was printed in an old LGB Telegram magazine.






















Jerry


----------



## Dan Pierce (Jan 2, 2008)

If you have the LGB mogul, or F7B, the rpm sensor is a sensor on the axle so full track power will work just fine on these. However the start up direction will not work properly. (2 blasts forward, 3 for reverse). 
Reed sensors can have relays for activation of the sounds, or just keep using the magnets. 
Some other LGB engines have this feature with axle sensors. 

Phoenix units are DCC, but you need to have a switch to make sure you can disconnect the Phoenix when reprogramming the engine decoder. 
Phoenix can be programmed from their software via the serial interface.


----------



## rreiffer (Jan 14, 2009)

I agree with Scott, if it's an engine I don't want to stick a fortune into I put the existing sound system in parallel with the motor.


----------

