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MRC 16-bit sound decoder in Atlas RS-3

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  • MRC 16-bit sound decoder in Atlas RS-3

    Ever since I first tried switching with a sound-equipped loco, I've been on a quest to match the prime mover noise with prototypical switching.

    The first problem is getting the prime mover to rev up before the loco starts to move. Most engineers throttle up to at least Run 4 when light, Run 8 if coupled to anything heavy. The slack doesn't even run out for 5 seconds or more.

    Some sound decoders support manual prime mover notching. I don't like this because I have to keep track of both notch and appropriate speed. All very well if I'm putting on a show for somebody else, but not so hot if I'm the audience.

    In the Bachmann RS-3 and the Atlas HH-660, you can get a tolerable approximation by setting a rather slow acceleration rate and throttling up to speed step 25 or so. With Athearn's Genesis GP-9, acceleration rates slow enough for the diesel to rev before movement aren't very practical when doing actual switching.


    The second problem is what happens when the loco gets rolling. Working in level yards, the engineer almost always throttles back to idle and drifts along until it's time to apply the brakes.

    Some people do this with manual notching, but see above. None of the decoders I've tried can address this with the deceleration rate; in many cases the prime mover RPM is tied to the track speed.

    So I was quite interested when MRC advertised decoders with an operating brake function. It sounded like I could prototypically open the throttle to accelerate, shut off to drift and apply the brakes as necessary.
    James


  • #2
    I had read a good deal of on-line criticism of both the older MRC decoders and the current 16-bit sound decoders. But when an Atlas RS-3 came my way, I shelled out $56 (including shipping) to TrainTek for a #1622 "Drop In Alco 244". Here it is with Miniatronics YelloGlo LED headlights and 470 ohm resistors.



    The included speaker is about 22mm in diameter and isn't going to fit anywhere in the RS-3 unless I do a major milling job on either a weight or the underframe between the trucks. It's mounted to the board with a bit of double-sided tape for operational testing while I await a speaker that will fit in the cab roof.

    And now I'm going to talk a little about MRC product management. The people handling their DCC decoders are either very overworked, or they should seriously consider some other career:

    1. The package's label says "16 Bit Drop In ALCO 244". It does not say the board is dimensioned for Atlas, neither does their web page for it, nor their on-line Decoder Selection Chart. It fits my RS-3 and looks like other Atlas boards, but this is something I found out from MRC resellers, not MRC themselves.

    2. Neither the web site, the packaging nor the manual give dimensions for the speaker. The paper manual does say it's 8 ohm impedance.

    3. The manual is more informative than some competitors, but it's a single tri-fold page covering 6 products. It says 'Fits Many Atlas/Kato/Athearn/Intermountain Locomotives'. I was most annoyed to be told which CV selects bell and horn type, but not what sounds are selected by which values. Yes, I'm old enough to have heard real B&M RS-3s 45 years ago. I think the horn I can only describe as '3 chime' (CV50 = 1) is the closest, but I could easily be off in the weeds. And I have no idea which of several single-chime horns is closest to what Atlas put on the model.

    4. The manual doesn't document the polarity of the motor terminals. It does for the light terminals and pads. And available lighting effects are also documented.

    5. When you download 'resources available', you get the same generic manual. C'mon, guys, web content only costs you the writing, and someone, somewhere wrote a set of specs good enough to get this manufactured.
    James

    Comment


    • #3
      Yeah, not much help are they. This and other decoders will short on turnouts and drive you nuts. There is no keep alive circuit of any value. That cap on the board is for the sound not the motor. That means it will stop and start on the very slightest dirty track or hick up in power pick up. They also must have gotten a deal from the greeting card people for their speakers. They all seem to be the same size. It is an Atlas style board made for those decoders that have the clip for the board. So that part meets the 'drop in' advertising of the decoder.

      There is only one real way to get the speaker in there and that is buy a speaker that will fit because that one isn't going to. An oval speaker is the one I use for this. RailMaster DS1436-8 8ohm 1.5 watt 14mm x 36mm x 10mm (0.55" x 1.41" x 0.39") or Soundtraxx 14mm x 25.5mm Oval Speaker part #810112 The Railmaster does come with an enclosure. Fortunately this is an 8 ohm speaker load and is common. You will have to make the enclosure fro the Soundtraxx as they don't have one yet. Just the gaskets. Either way your going to have to mill or cut down the weight in the long hood end. A band saw makes quick work of that. Don't use a Dremmel type tool as this will just take too much time. A hand hack saw or coping saw will work better if you don't have a small band saw. I leave a shelf for the speaker to sit on. Be sure that it doesn't stick up much past the top of the weight because there is not much room. This may sound counter intuitive but I mount mine facing down. You get more bass out of it that way. You can drill holes into the platform but I use a speaker gasket or a couple of pieces of plastic as a spacer. Lately I have been using just double sided tape on the outer edges. Holds fine. You can do it this way or drill out the chassis in the fuel tank for the speaker. I tend to leave the chassis alone and use the weight for the modification.

      I also use the Soundtraxx TSU1000AT sound decoder for Atlas engines. Superior sound and motor control. This is one of those cases of you get what you pay for.

      Bill

      Bill Shanaman

      New Haven RR

      Hartford Division

      in Colorado.

      Comment


      • #4
        You would absolutely love the new Loksound decoder for the RS3 - same one Atlas now uses in their latest factory offerings. Very realistic sound to movement relation.

        Mark.

        Comment


        • #5
          Bill, once I figure out what connector to order from DigiKey, I will try different speakers. I found a conversion SBS using a TDS Mini-Oval under the cab roof. Do you think milling the weight gives enough better results to justify the loss of traction? My mill will make short work of the job if I decide to do it that way. I also looked at milling the frame, but that seems to cost me at least one of the motor mounting screws.

          Mark, I'll take a look at the Loksound.

          I compared some of the MRC 1622's configuration with the defaults printed in the manual and everything matched. So I tried running it. The default horn is a 3-chime, the default bell is rather slow, the default starting voltage of 20 produces about 5MPH at speed step one. The prime mover sound with the shell off is quite tinny compared to a stock Bachmann RS-3. I won't know how it sounds with the shell on till I get a speaker that fits.

          Something's wrong with dual-mode: When I connect DC, the prime mover sound starts up but the loco never moves. I've emailed TrainTek asking for suggestions, but DC function would mostly be a convenience for wheel cleaning. I have more than enough DC locos if it's just me running - this one is only needed for DCC op sessions.

          But what I bought this for was to try out the F5 "Service Braking" function. With starting voltage of 2, acceleration of 60, deceleration of 63, switching moves generate reasonable prime mover sounds: From a stop, the diesel revs before the wheels turn. When up to speed, throttle to 0 brings the diesel back to idle quickly. F5 can make wheel squeal, dynamic brake or be silent, but it slows the engine. I'd be happier if the deceleration could be reduced to Genesis GP-9 levels - I had them coasting a scale mile late in my experimentation. But I'm not going to junk the decoder.

          My coolness toward it comes mostly from the lousy job of sound editing MRC's engineers (or contractors) did. And yes, before I was a Product Manager I wrote and maintained a production sound editing program. They don't have enough samples to cover all running conditions. This is most evident if the RS-3 is moving at speed 10/28 on level track: the prime mover sound goes up and down every few seconds like the microcode is using an 'accelerating slowly' segment. There are also a lot of anomalies when decelerating - turbo and diesel revs kicking up, then dropping, then kicking up again. I won't knock them for the tinny sound until I try a better speaker, but Bachmann achieved a much better "Alco 244" presence in their inexpensive offering.

          MRC's web site reports the #1622 as out of stock. It appears they have replaced some 1600-series parts with 1800-series parts. I may try one of the newer ones next. But right now I'm thinking that it's a shame that the innovative F5 "service brake" idea wasn't accompanied with more polish on the overall product.
          James

          Comment


          • #6
            Why do you need a connector? To remove the body? I found mounting the speaker to the weight means you don't have to worry about that. Milling the weight will not adversely affect the traction or pulling power. Sure you may lose a car or two but overall if it is anything less than 1.5% grade you won't notice a difference. You can trade mounting screws for double sided tape or silicone glue. As long as the drive train is level you should be OK.

            Dual Mode. Something they don't tell you, and other dual mode decoders too, is that you need straight filtered DC. No pulses or waves. And something above 8 or 9 volts just to get the motor turning. That sound eats up a lot of the voltage before getting to the drive section of the decoder.

            I don't know if you researched this or not but Soundtraxx, Digitrax sound bug, TSC WOW!, QSI Titan, LOK sound and MTH all have 'service brakes' with squeal sounds. I am a Soundtraxx brake user myself. It is really nice to switch with. Half my crews hate it because of the momentum you need to make it work well. I use NCE Cab04/06PR radio throttles and have the brake remapped on F7. They originally come on F11 so you have to remap as those throttles do not have an F11 except the Cab06 where you have to take extra steps to get to F11. Why when you can put it on a usable function key. F7 is the alternate and is available on all throttles.

            I can see why you want to keep the MRC decoder and just change the speaker. The Soundtraxx 810112 speaker is the best fit I have found for the RS3 narrow hoods. Bill
            Bill Shanaman

            New Haven RR

            Hartford Division

            in Colorado.

            Comment


            • #7
              You're right, Bill, there's "F11 Train Brake" on page 53 of the 66-page Soundtraxx manual. I suppose if Linn Westcott was a centenarian, I'd have seen an article about using it and there would have been pressure on the manufacturers to standardize on a common Fn key. As it is, I'll have to think about annoying my visitors while pleasing myself.
              James

              Comment


              • #8
                The circuit diagram I made as the final bit of prep for my NMRA EE AP certificate:



                Thanks again to Dwayne Ward for the electric symbol parameter file.
                James

                Comment


                • #9
                  I may not be any help to you, but for the speaker in my Atlas RS-3, I cut out the exhaust hole from the shell and installed a Detail Associates HO #229-2702 Air Grill. Drilled/countersunk a 3/4" hole into the top of the locomotive weight and dropped in a Soundtraxx 3/4" speaker.








                  Louis L&R Western Railroad
                  Pacific Northwest Logging in the East Coast

                  Comment


                  • #10
                    That looks pretty good. Does it fit the drill hole tight enough so it acts as an enclosure too? Do you like the sound?
                    James

                    Comment


                    • #11
                      quote:


                      Originally posted by jbvb


                      That looks pretty good. Does it fit the drill hole tight enough so it acts as an enclosure too? Do you like the sound?


                      Yes, indeed it does work outstandingly well, and sounds great. I tried the speaker with face down into the hole and face up. Both ways seemed to sound the same. Ever since MRC started mounting their speakers face down into the speaker boxes, I always test both methods on my installs. This RS-3 install I went with the speaker face up. As long as the speaker pressure is less on one end, the sound will work just fine on the opposite end of the speaker.


                      Louis L&R Western Railroad
                      Pacific Northwest Logging in the East Coast

                      Comment


                      • #12
                        quote:


                        Originally posted by desertdrover


                        I may not be any help to you, but for the speaker in my Atlas RS-3, I cut out the exhaust hole from the shell and installed a Detail Associates HO #229-2702 Air Grill. Drilled/countersunk a 3/4" hole into the top of the locomotive weight and dropped in a Soundtraxx 3/4" speaker.








                        Louis, I forgot about those. Nice suggestion.

                        Bill
                        Bill Shanaman

                        New Haven RR

                        Hartford Division

                        in Colorado.

                        Comment


                        • #13
                          I measured my RS-3's weight and it was too narrow to drill for an 18mm speaker as Louis suggested; 15mm might not have broken out the sides of the hole. So I got a mini-oval & enclosure after all. The other night I got back to this and was glad I own a milling machine:



                          Once with a 3/16 end mill to make room for each LED headlight's resistor. Several more cuts with a 3/8" end mill under the cab (rear weight's mounting screw area, shown) to make room for the speaker & housing. Then a while with a hobby knife cutting out the top & sides of the shell to match.

                          The prime mover sound is not wonderful through any speaker I've tried, but I'll just turn down the volume. Bell & horn sound OK. I continue to like the way the prime mover goes to idle when I throttle back, and the F5 brake function.

                          More generally, I find current Chinese-produced HO locomotives to be a mixed blessing. They look good, run well and are generally a good value. But the designers didn't give a damn about taking them apart. In this case, I broke at least one tab off the shell each of the 3 times I removed it from the chassis. Glued back on, hope they'll hold. I also broke one set of latches on the fuel tank molding, so I got out the Goo. Broke the wire off one brush's tab too. But now it's in service until something inside wears out.

                          At least it isn't like my Athearn USRA 2-8-2, which developed an intermittent short after I had to take it apart, and has been in its box for about 10 years, waiting for me to find the patience to address it again.
                          James

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