Atlas GP-38 sound decoder install project

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IronBeltKen

Lazy Daydreamer
I've been dragged kickin' and screamin' into the Dark Side, but I'm slowly adapting. I finally installed a Soundtraxx LC decoder and speaker in my Atlas GP38, they had been sitting on my shelf for over two years. Even though I started the project on Friday, honey-dues kept springing up like mushrooms and I could barely find time to work on it.

Originally I thought I'd have to grind away the top part of the rear weight to fit the speaker enclosure. But when I got the weights off, and saw the the Soundtraxx decoder was slimmer than the light-control PCB I was replacing, I realized I could fit the speaker directly on top of the decoder if I arranged the wires correctly.

First, here's a shot of the components I needed to install:
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/soundtraxx_LC_and_oval_spkr.jpg

I spent over 30 minutes trying to get the shell off, the explosion diagram wasn't much help - but finally I prodded in the right place and it was all downhill from there. Here's a pic of the shell with the tabs so you don't have to go thru what I did:
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/soundtraxx_in_GP38_001.jpg

With the walkway still attached, and me not having experience dissembling the newer Atlas locos, I didn't realize the wieghts could be separated from the frame - but a friend on the Atlas forum set me straight on that:
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/soundtraxx_in_GP38_004.jpg

This was the first time I had to deal with an install that involved soldering, so I was a tad nervous. Nothing like a pair of helping hands to keep things steady:
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/helping_hands_and_spkr.jpg

Before I could go any further, I needed to make an enclosure. The following 3 images show the box taking shape:
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/speaker_and_enclosure_001.jpg
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/speaker_and_enclosure_002.jpg
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/speaker_and_enclosure_003.jpg

A final clearance check:
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/speaker_and_encl_clearance.jpg

No pics of the soldering, I was too stressed out to do that. After I did the initial test, one of the speaker wires broke off on the decoder end as I tried to get the shell back on...sweet! I ended up shortening both wires, resoldering them wasn't as difficult as I'd feared. Here's how everything looked before the shell went back on:
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/speaker_in_GP38_001.jpg

The next image shows where the speaker sits: almost, but not quite directly, under the dynamic brake fan. It's see-thru, so the sound has a way of getting out.
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/speaker_in_GP38_002.jpg

I'm not sure if the Trainman geeps have see-thru d/b fans or not - if they don't, then it may be a good idea to get a Cannon fan to put over that spot. Otherwise the sound may be muffled.

Here's a final shot of my GP-38 reassembled, after successful testing, just so you know everything did fit inside there.
http://i39.photobucket.com/albums/e182/CSX_road_slug/electronics/speaker_in_GP38_004.jpg

That Soundtrax LC decoder seems awfully quiet compared with QSI and Digitrax sound decoders, at full volume it's just loud enough to sound good. But I've got to admit, it's the best at reproducing the 'bark' of a normal-aspirated EMD prime mover, of any brand decoder I've heard so far. The diesel Tsunami just can't get here soon enough!
 

Smoke

Southern Railway lives on
Thanks for the tutorial. I can't wait for the Tsunami either. I'm going to install sound in my SD75M when they come out with the Tsunami.

-Smoke
 

jbaakko

Diesel Detail Freak
I'm waiting for the Tsunami's too. I've been holding out on DCC'ing & sound adding until that. Beyond that, I'd be trying out the Loksound ones, I think I'll toss one in the SD60M...

Anyways, looks awesome, keep it up!
 

IronBeltKen

Lazy Daydreamer
I plan on having a closer look at the LokSound myself.

I sure hope the recent lawsuit against Atlas and QSI doesn't delay the release of the Diesel Tsunami even longer...!:mad:
 

SpaceMouse

Fun Lover
I met with a LOK sound rep at a recent regional NMRA show. Their system of having several basic decoders that are programmable is a great system. I was convinced that I could get the sounds I need for my old-timers from their website.

The only drawback is the programming interface that you have to buy. IF you are going for a lot of their decoders it might be worth it, but if not then it is cheaper to go with a Tsunami.

Maybe Digitrax will eventually get off their butts. I have an Loconet interface already.
 

RexHea

RAIL BENDER
Thanks Ken for the excellent step-by-step info. I used an "LC" in my P2k GP7. Like you, I love the sound even though it is not as loud as other decoders. I believe the LC has about 1/2 the power output as the QSI, the old DSD150, and the Tsunami.

One easy method to getting "bigger" sound is to have as large a baffle as possible. I was able to boost the sound level by using a larger homemade baffle installed in the cab. That is about the only place with enough room. Of course this wouldn't work if you like to see an engineer at the helm:eek: :D .

Oh yeah...at least you got your body off without breaking any tabs....ho hum de hum:rolleyes: :D :D
 

jbaakko

Diesel Detail Freak
Thanks Ken for the excellent step-by-step info. I used an "LC" in my P2k GP7. Like you, I love the sound even though it is not as loud as other decoders. I believe the LC has about 1/2 the power output as the QSI, the old DSD150, and the Tsunami.
I'm assuming that could equate to less power draw, meaning more units running before you trip a transformer?

I myself intend to have the volume set a wee bit low, as to not overpower everything in the train room.
 

RexHea

RAIL BENDER
Josh, in this case, I doubt the audio power difference would be significant enough to be a factor with the total power. I haven't measured so as a wild guess, maybe a few tenths of an amp in current.

Yeah, I used to run my locos with the sound blaring wide open and thought it was really cool with several locos yelling at me. After awhile and after near deafness, I started turning them down to less than pain level.

It was so-o-o-o loud: When I tooted my E7 horn, the proto trains on the track 1/4 mile away would toot back:eek: :D :D
 

IronBeltKen

Lazy Daydreamer
Rex,

You mentioned using a larger baffle to improve the sound volume; now I'm wondering if I should double the depth of my enclosure from 1/4" to 1/2", and place it with the speaker facing downward in the rear. I'd have to cut-away some of the weight for it to fit there, but adding a little more length of speaker wire won't be difficult.

Do you think the gain in sound quality would be worth the effort?
 

SpaceMouse

Fun Lover
Ken,

I talked with a SoundTrax tech rep and I got the distinct impression that it was the nature of the beast and other than turning the volume all the way up, I was stuck with what I have.
 

IronBeltKen

Lazy Daydreamer
Ken,

I talked with a SoundTrax tech rep and I got the distinct impression that it was the nature of the beast and other than turning the volume all the way up, I was stuck with what I have.
Yeah Chip, that's exactly what I'm doing but it still isn't quite enough. Somebody on the Atlas forum said that using a deep enclosure could yield an additional 3 decibels of sound - seems a tad farfetched to me, though!
 

RexHea

RAIL BENDER
Like Chip said, it will never be as loud as a QSI. However, we can make it somewhat louder with the baffle. Ken, I did a lot of experimenting with this beginning with cupping the speaker in my fists. You will notice a huge difference in the volume when it is cupped versus not. You can also try sealing the speaker in some kind of container just for the experiment. What got me thinking in this direction was the BLI units. There is no baffle built on the speaker; it uses the entire loco shell. Well, we can't do that, but we can try to make the baffle as large as will fit.

Everyone concentrates on having the speaker sealed to prevent front/back cancellation, but it is also important to have enough air behind the speaker to allow full and non-restrictive movement. Your addition of 1/4" in depth will make a considerable difference, but you need to perform a few experiments yourself.

The so-called speaker baffles that you buy from "Tony's" (and others) are too shallow. What I did for my GP7 was use their baffle for a form, cut the backside away, and added a styrene made extension box. The volume doubled. Also, I used a pill bottle cut in half with a round speaker in my FA unit. The FA uses a DSD150, but again the sound doubled versus a smaller baffle. Don't worry about the speaker pointing down as many do this and I sometimes believe it provides a better sound. I wouldn't be concerned about cutting away some of the weight in the loco, as many after-market installations require this in order to make a fit. You can always add weight later in other places, if this becomes necessary.
 
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Cjcrescent

Master Mechanic
Instead of a pill bottle, I have read of others using an old 35mm film container to make a baffle. I believe it was in reference to an installation in a steam tender. Not sure if the "can" would fit a scale width shell.
 

IronBeltKen

Lazy Daydreamer
... addition of 1/4" in depth will make a considerable difference, but you need to perform a few experiments yourself... What I did for my GP7 was use their baffle for a form, cut the backside away, and added a styrene made extension box. The volume doubled. ...
Muchos garcias Rex, looks like [a larger enclosure] is what I'm gonna do! I'll let you guys know how it works out...
 
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