View Full Version : N scale sound decoder and GP-35?

June 30th, 2012, 10:53 PM
I am looking at getting a Atlas GP-35 with a MRC drop in sound decoder. Just checking if they are truly drop in. If they say Atlas GP and others, does that cover "this" GP engine?





jagged ben
June 30th, 2012, 11:22 PM
The MRC sound decoder is not truly "drop-in." The circuit board will replace the existing circuit board, but you will have to mill the frame in the fuel tank area to make space for the speaker.

Later versions of the Atlas GP-35 should be 'DCC ready', some earlier versions were not. It is suspicious that the features listed for the one you linked to do not include "DCC ready", I would be wary of that particular item unless the vendor will confirm for you.

July 1st, 2012, 05:49 AM
Uh Oh Buzz! MORE N-scale! I like that! N-scale sound is what sold me on finally bowing to the DCC gods. The Atlas geep-35 is a nice engine. However, the MRC decoder you're looking at is not what you want, since it is NOT "drop-in" since, obviously, you've got to mount the speaker somewhere, which is usually accomplished by milling the fuel tank to make room for it. I also believe this decoder is a discontinued item (at least according to Brooklyn Locomotive Works).

If it were truly "drop-in" then you wouldn't have to mill anything.

MRC does make a drop-in sound decoder that will specifically fit the Atlas geep-35. Its MRC number is 0001955 and is listed by Brooklyn Locomotive Works as a replacement for the MRC #0001636. It has a tiny, "high fidelity" speaker mounted directly onto the board, and specifically states that it simply drops into that engine.

I have heard (no pun intended) that the sound quality on these latest MRC decoders can be improved somewhat by doing two things. (1) building a speaker enclosure out of Styrene on the backside of the speaker, and (2) opening up the plastic fan housings on the Atlas engine body and replacing the cast plastic fans with BLMA etched fans to allow the sound to escape the body.

Of course, better sound is always a product of a bigger speaker, and although I would like to say that you can buy a milled frame from Aztec Manufacturing if you want to replace the teeny speaker with a larger one (by placing the new, bigger speaker in the fuel tank area), after visiting the Aztec site, I do not see a GP-35 frame shown as being available. You would have to do the milling yourself, which could be done with a diamond cutter on a Dremel rotary grinder if you were careful and took your time. There are any number of larger speakers available that would fit the fuel tank area...some are round, some are oval, some are rectangular or square. To get the best quality of sound, a tight, sealed speaker enclosure is essential, and they are available from several DCC sound manufacturers that fit their speakers precisely.

My experience with MRC decoders has not been good. They are notorious for having "bugs" and "incompatibilities" with Digitrax and NCE systems. I am replacing all of the MRC sound decoders in my Athearn Big Boys and Challengers because they fail, and melt the tenders! After testing a Soundtraxx Tsunami in one of my Big Boys and directly comparing sound and operation with my other Big Boys that have the stock MRC decoders in them still, the Tsunami is exponentially better in every way than the MRC decoders...that's WAAAY better than the MRC decoders, which sound toy-like and offer extremely limited operational realism.

However, I have heard that the newest MRC decoders sound better, are more durable, and have fewer "bugs". However, that is just rumor and I have no experience with the new MRC decoders.

Hope this assists you!

Bob Gilmore

July 1st, 2012, 03:39 PM
What started all of this again was I bought a F59PHI Rail link in HO. I put in a MRC sound decoder and that is all she wrote. I was hooked after the first time I heard the horn blast. Then I turned on the bell, the lights and ran the engine up and down a single piece of flex track. So, if I do go N scale I just have to have the DCC and sound. To me it adds so much to the fun of watching the trains run around. Way back when I bought a MRC Prodigy Advance. It was on sale and was less then half the price for the Digitrax set.

If all I have to do is grinds out, mill, drill, chisel, hammer, blow torch, dynamite a spot for the speaker in the fuel tank area. I think I can handle that.

I was looking at a place that offers the install of a sound decoder. It was about $200.00 plus the cost of the loco. Little rich for my blood.

Of all loco's out there, the GP-35 is by far my favorite. A close second place is the GP-38's. I have no idea why I like them over any other engine. But I do. So, I will now go look at Brooklyn Locomotive Works and see what they have.



July 4th, 2012, 09:06 AM
I have 9 MRC sound decoders (all drop in) in both Kato and Atlas diesels. The quietest of all the decoders is the 1955 model which is in a GP7. Barely audible. Cannot recommend. However, in an Atlas GP-35 you may get a better result because because of the shape of the loco body. For example, in an Atlas H15-44, the sound from the decoder is very loud and I believe it is the shape of this model's frame that provides good resonance (this is an 8 bit decoder, and not the 16 bit one which are the replacements). And don't waste time and money replacing the speaker with an 8ohm one. Doesn't improve the sound. 16 bit speakers for their size are OK.

Overall, I am very pleased with MRC sound decoders, and can recommend. If you get the 1955 sound decoder and it is not loud enough, send it back and get a replacement. MRC warranty is very good and I have found them an easy company to deal with.

I am operating a NCE ProCab and have no problems with reliability.

As an aside, I purchased three HO stationary sound decoders and I have installed these in various parts of my layout, and while the sound doesn't travel around the layout as with a mobile decoder, the sound from the HO speakers is terrific and adds to the realism of the layout. Also stationary sound decoders are half the cost of the mobile ones.