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If willing/able to go the DIY route, there have been OGR threads showing how to use low-cost MP3 players or MP3 sound modules.

mp3 player in s

I don't recall an S-gauge example off hand, but above shows one approach.  This particular MP3 player is a ~3cm cube.   As you can see, the speaker itself is not that large so I wouldn't call it room-filling sound. The tiny battery lasts maybe 1 hour or so before requiring recharging.  I've always taken out the guts to change the power source, speaker, on/off control method, etc. to meet a particular application.  This does require scrounging the web or "ripping" a Christmas CD to assemble your mix of MP3 music.  A $2 memory card holds hours or weeks of music so that's not an issue.

128mb microsd memory card


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Last edited by stan2004

Ray (and Stan) - have you considered getting a bluetooth speaker system?  that has the obvious advantage of simply using your iphone or computer as the source.  There are a couple of stereo BT systems on Amazon that look like they'd fit in a boxcar - or perhaps better yet, make them a flatcar or gondola load, which would make changing the batteries easier.  I guess you could get fancy and figure out a way to power it up from track power.

diy rolling stock mp3 player possibly fits S gauge boxcar

Using stuff I had lying around, here's a video of one approach.  Yes, there are i's to dot and t's to cross but with some DIY persistence I think it could be done for a modest out-of-pocket outlay of cash.

An AC-to-DC voltage converter takes AC voltage from the operating-car's power pickups and converts to DC - set to 3.8V.  I removed the tiny Lithium 3.8V rechargeable battery and wired the DC output of the converter to where the battery was attached.  I then attached a larger speaker than the stock tiny speaker (8 Ohm).  Technical note: the board has a type 8002B audio amplifier IC chip.  It is important to use a baffle (chamber) for the thin speakers that might fit in a S-gauge car; it doesn't have to be fancy as illustrated by the vitamin bottle neck.  The video doesn't show it well but messing with the baffle can have a dramatic difference in sound volume and bass.

I confirmed there are buckets of "free" downloadable Christmas songs in MP3 format on the web.  I placed a couple along with some other train related MP3 sounds to illustrate the concept.  The photo shows the directory of files on the microSD card; I think it's common knowledge (?) that a convenient way to transfer MP3 files to a microSD card is with an SD-adapter as shown in video.  Most, if not all, MP3 player modules simply cycle thru all the files on the memory card.  In the video I am pressing the "next song" button to move things along!  In this case you simply apply power and it just starts playing.

The crossing bell MP3 "song" was leftover from an OGR thread on a low-cost DIY crossing-bell sound accessory.  It reinforces the concept that an MP3 player, typically associated with playing music, could be re-purposed for non-musical layout sounds.


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  • diy rolling stock mp3 player possibly fits S gauge boxcar
Last edited by stan2004

Stan, Wow that looks like it might even fit into HO. Thanks for showing this, I am not an electronic wizard, your mention of the type 8002B amplifier IC chip, not sure what that would require in the build, maybe the ohm rating of the speaker?  I really do appreciate you doing this illustration for me and I am sure others will pick up on this.

I may come back to you with some questions on this.



8002b chip

The 8002B is already on the board of the cube-player.  I made note of what's on the board as this would be one of the first questions a hard-core DIY'er might ask since the audio amplifier capability governs the choice/range of speaker Watts, speaker Ohms, etc.  A PDF datasheet is attached - I only include this as background.  For your application, you can ignore the techno-babble.  Just put in a larger 8 Ohm speaker that fits.

If you are seriously considering this, I will assist you in identifying suitable items.  I am an eBay addict and don't mind waiting weeks/months for "free shipping" from Asia to save a buck.  But if this is for Christmas 2020, I suppose you ought to consider domestic sources though prices are generally 2x-3x YMMV.  I've noticed that more and more of the eBay electronic stuff relevant to OGR projects can be purchased from Amazon that qualify for the $25 free shipping and/or Prime.

Also, it helps to know how this will be used.  That's what I mean by i's to dot, t's to cross.  For example, will the car ever run on a track with DCS?  If so, there's a 25-cent "DCS choke" that should be added.  Except you can never buy just one DCS choke without incurring huge minimum qty or shipping overhead.  How exactly do you want to turn it on/off...or maybe it always runs when on a powered track?  Do you really NEED (or just WANT) volume adjustment?  And so on.  This is all part and parcel of the DIY adventure! 


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Last edited by stan2004

Stan ,

I do plan to build this, I don't have DCS, but I would likely run it on both Legacy at 18v and if possible on conventional/ variable voltage. I would probably use a slide switch mounted on the chassis to disconnect power from the track and be able to operate silently if need be. I understand the EBAY addiction, I spend more time there than I should. I do appreciate any help you can give me for aquiring the proper materials.


DIY ebay mp3 player

The MP3 player itself and microSD memory card are widely available on eBay; they are duplicated on the right above.  I figure you might already have a microSD-to-SD card adapter to allow plugging the microSD card into most laptops to load your sound files. You didn't specify how anxious you are to get this going, but if coming from Asia your Christmas might be a Silent Night.

I found a guy in the US selling a pair of wired 8 Ohm 28mm speakers removed from equipment.  $3 each seems to going rate even on eBay Asia for 28-30mm speakers.  There are train sellers of "premium" HO or even S sized speakers but that's a different discussion.

The AC-to-DC converter is not the exact one I showed in video but is the same width (just under 30mm).  I was targeting 30mm as a "safe" maximum dimension to fit in an S boxcar.

This project does require soldering - to remove/replace the battery and the supplied speaker.  And you do need a voltmeter to set the output voltage of the AC-to-DC converter to 3.8V (to simulate the battery).  I assume you can come up with an on-off switch and splice it into the power supply path.  I figure you can cobble together some kind of speaker baffle/chamber using household items; I suppose you can open the boxcar doors to let the sound out...or drill holes in the chassis floor as many sound-cars do.

Yes, there always seems to be "one more thing."  But if you, or anyone else for that matter, are still interested in pursuing this, let the games begin!


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  • DIY ebay mp3 player

But wait, there's more!

diy ebay mp3 player with volume control

In the 2 birds with 1 stone category.  For just over $1 w/free shipping (from Asia) you can get an amplifier module with rotary volume control.  Obviously the volume control can double as an on-off switch in that turning to minimum volume effectively turns the music off.  The additional module is powered by the 3.8V from the AC-to-DC converter.

Also, I show the actual recommended AC-to-DC converter in the previous post.  It's very similar to the one in the video but always good to see proof of concept with the real McCoy!

In the fine-print department, the MP3 cube player has a +VOL and -VOL button.  It remembers the last set volume between use...but if you want to change the volume it can be inconvenient to access the silver mini "buttons".  Hence for the modest additional cost, real-estate, and just a few additional solder connections, I recommend the volume control module.  This also goes to the occasional OGR topics where someone wants to know how to turn down the volume on some particular layout accessory.


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Thanks for the additional information ànd parts post.

Sorry for not acknowledging sooner, winter on its way and needed to be in the yard before I get buried with the white stuff. I am wanting to get this for this Christmas, once parts arrive l will be at this hot ànd heavy. I see out my patio door that here in Genesee it is getting white out there now.


Hi Stan,

The inside width of the car shell that I propose to use is 39mm, the interior length is182mm between the mounting posts and the interior height is 38mm. The chassis of the donor car is of sheet metal construction. The chassis is  from a Gilbert AF operating box car and the shell that I will use is from a Lionel Flyer Christmas car. The shell and chassis will fit with minimal mods to the chassis.  I am considering using a dc-dc buck converter and putting a 1000uf 35v cap between the rectifier and the buck converter to even out the power in the case there may be dirty track,  might that be a good idea or am I all wet?

You're definitely on the right track.

ac-dc vs dc-dc with loose parts

If you are comfortable working at the component-level (i.e., soldering, wiring, etc.) your options expands greatly!  That is, physically separating the bridge rectifier and large input capacitor provides more mounting options.   For example, there is a 1000uF capacitor on the AC-to-DC module which is the tallest component.  But options expand if you can mount it, say, sideways.

Your dimensions seem more than adequate but it's funny how when you actually start installing, wiring, and so on the space seems to vanish!


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Last edited by stan2004
@RickO posted:

There's an o Guage boxcar  Christmas music system"take out" on the FS forum now if it'll fit.

Maybe ask the seller for the dimensions.


Thanks for the heads up on the for sale forum. I am going to build a car up as Stan has shown. I am not sure all the parts will arrive by Christmas so I purchased one of the takeouts that were for sale, kind of a bonus I'll have two musical cars.


What did you decide to do about a speaker?  And do you plan drill or punch out the chassis to mount the speaker downward-facing on the chassis floor?

While you're waiting on components, I'd think this would be the perfect time to assemble your Christmas music MP3 files.  This would be a good time to resolve any issues with the MP3 side of things. 

I have the pair of speakers that you recommended on order, not sure yet, may mount to the ends of the car and drill a number of holes there or to the chassis, it depends on the fit. I can experiment with a junk body and temporary install to find how the end mount sound works out.

Yes when the player arrives I will attempt to start putting that together.

Will keep you posted on progress.


Ray, I have been following this thread and hope the project works out for you. I was slow responding until I began thinking about my own Christmas projects.

Lionel made an S gauge Christmas Reefer that plays Christmas music. It is part of set 6-49621 from the 2009 Vol. II catalog. I have attached some information about the set and the reefer. As far as I know none of these cars or the engine were offered for separate sale. A similar engine was cataloged, 6-48059, but that engine is numbered and painted differently. I have the set but have never opened it, it is MSOB. I did inspect an open set and saw all the contents. The other feature of this set is it includes a circle of 27”R curves with Lionel stamped on the ties rather than K-Line.



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I see that Lionel car uses a 9V battery.  Track power vs. battery seems to be the first decision to be made for DIY sound boxcars.  I seem to recall OGR discussions where the cost of retro-fitted powered trucks if not starting from a so-equipped operating car well exceeds the cost of the sound generating electronics!

A typical alklaine 9V battery might be rated, say, 400 mA-Hrs.  Let's say the electronics draws 40 mA while operating.  40 mA x 9V = about 1/3rd of a Watt of power.  That's probably about right for some background Christmas music.  That would be 10 hours of operating time.  Seems reasonable.

If going the battery-route with these MP3 modules, note that the scavenged MP3 players were designed to operate on a rechargeable Lithium battery.  All the MP3 players I've seen have a USB charging port just like a cell/smartphone.  I recall though that cheap MP3 players typically have only a crude battery charging circuit...rather than the "smart" chargers that automatically know when to stop charging.  So if going the battery route, do your due diligence!

Last edited by stan2004

I have been away from the forum for a couple days, came back here and I see I have received some more information about these projects.

AmFlyer, Hey, thanks for posting the illustrations of the car with the instructions. I was wondering where Lionel had placed the speaker, I see it's over the truck. I was also wondering about the battery replacement, pulling the shell makes that simpler. This helps me to move along with the car for which I acquired a Lionel Christmas music system that came out of an O gauge car.


Yes on the car that is going to get the MP3 player that will use track power through a buck converter, I am planning on removing the battery and wiring from the buck to the MP3 player as you illustrated in one of your pics above. I am still waiting for some of those elements, thus the desire to do the battery powered car to be sure of having one musical Christmas car this year. Besides with the MP 3 car I can change the card and thus play railroad music the rest of the year.

This is a fun project, they both are and I want to thank everyone for their input.


Hi guys, Back again.

I received the MP3 player and the card, I have the music on the card and tried it in the player, all is good. I am now waiting for the amplifier, than will be complete. I have decided to put this system into the Polar express coach. The coach already has the power pick-up trucks and there is plenty of room for this setup. Hopefully the amplifier will arrive in time for Christmas. I will keep you posted on the progress.


Last edited by Rayin"S"

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