Adding sound to a SD-75i

Discussion in 'Z Scale' started by zscaler, Sep 3, 2012.

  1. zscaler

    zscaler TrainBoard Member

    I posted a link to my AZL CN SD-75i video ( yesterday and now I'm getting requests on how to do it.
    ESU makes the Loksound Select micro (73800 series) and you pick which specific engine sounds you want. I got the SD-70s sound installed and sent to me.

    Everything in the picture was included. I only had to solder on the speaker wires. The ID number on the chip is NOT for a SD-70 but a F-7 - another work in progress...
    The decoder comes with an eight wire plug which has been cut off (after testing on my DCC test rig which has the matching plug).

    I cut the enclosure into pieces to seal the speaker. In the next picture you see the speaker glued into the shell tilted as much as possible. The scrap pieces of styrene (enclosure pieces) were glued in to seal the back. If you want to get all the sound you can out of the speaker, you need the back sealed like the enclosure box does.

    Sides of the bottom frame removed right up to the car weight. This lets the sound out.

    The usual six wires (green and blue not used) are soldered onto the six contacts on the engine circuit board. Just like the TCS Z-2 is done.

    A notch is cut into the clip which holds the engine together. This is so the wires can angle down. Another notch is cut into the shell of the boxcar for the wires.

    Another notch is cut into the bottom of the engine shell to let the wires through. All the notches on the engine do not show and the engine could be put back to "stock".

    The wires fed into the top slot (well some).

    All the parts together.
    I did replace the yellow LED with a white one on the front. When I first assembled the engine, I glued the wires to the frame. Then I had to fix the engine and had to pull the wires loose. Found out I broke the white wire inside (front headlight did not work afterward) and I am replacing the whole white wire. I used a black felt pen to "paint" the "hoses" so it looks better.
    So you see how easy it can be to install sound next to any engine you want. THE AZL GP-7, GP-30 and GP-38-2 could all be done exactly the same way. There are other speakers available that are smaller and you could put it into a smaller boxcar.
  2. shamoo737

    shamoo737 Staff Member TrainBoard Supporter

    Thanks David. Its just the information we are looking for. Can you tell us what speaker you used and where did you order it from.
  3. zscaler

    zscaler TrainBoard Member

    The speaker came with the decoder. Sountraxx, ESU and Railmaster make different sized speakers. Anything over .50" (12 mm) will not fit in a standard car too easily. The oval speakers should produce more/louder sound than the round. If you were to remove almost the whole center section of a boxcar frame, you could have it extend down below the edge of the shell - just paint it black.
    I found the speaker available at:


    This one is even longer, but same width - more sound?

  4. zscaler

    zscaler TrainBoard Member

    ESU is supposed to come out with a 10mm x 18mm speaker - ESU 50329. That could be installed facing down in the middle of a car. I'm waiting for one right now. If you sealed the car up, the whole car could be the sound chamber. Hmmmm...
  5. kevsmith

    kevsmith TrainBoard Member

    I'm going DCC this Fall and this is very interesting. It is all new to me but I've been reading the NCE instruction book from cover to cover before I start on the locos of Shasta. Question is, could you fit sound decoders into the boxcar as a sound alone unit, picking up off the metal wheels on the trucks and fool it into thinking it is a loco and 'consisting it' with the loco in front. So it shadows the loco on acceleration etc without needing to be hard wired to it?

    second question. How much power take up does the sound need? I take it a booster for the NCE would become a neccesity


    By the way It's about time some more SD75s were available Rob!
  6. zscaler

    zscaler TrainBoard Member

    A five amp power supply can run many sound units. Maybe 1/4 amp per engine. At the most according to my rampmeter.
    Yes, you could put the whole sound decoder in a boxcar and get power off the wheels. But you would have to put a resistor on the motor leads so as to not burn up the decoder. That is why I like the follow car. Holds the decoder/speaker, but lets the engine pick up the power and drive the engine and lights.
    Be nice if they made a sound/function decoder. No motor leads but can be stand-alone in a car.
  7. pmx

    pmx TrainBoard Member

    FWIW, there are but they all seem to be for that Horribly Oversized scale. For example, the Digitrax has the SFX004 Soundbug that can be used in a stand alone configuration. It's designed to be used with their 165 series (HO) decoder, so it's ~17mm wide and 7mm high (So maybe.. it could be worked into an excess height boxcar?). But in a stand alone configuration, you just connect pins 9 and 10 to the track and address the device normally.

    Paul E.
  8. up mike

    up mike TrainBoard Member

    This is a Must Do Project for me now that I got to see Davids in Action :cool:
  9. zscaler

    zscaler TrainBoard Member

    Ed Turner checked with ESU tech support. They say you could put the decoder and speaker in any car and not connect with an engine. Just have power pick-up off the trucks and you could put the sound behind any engine. Then a simple consist is made up.
  10. CSX Robert

    CSX Robert TrainBoard Member

    The purpose of the resistor on the motor leads is not to prevent burning up the decoder, the decoder would be just fine without it. The purpose of the resistor is to make programming the decoder easier. The decoder will actually program fine without it, but the command station will not see the "acknowledgement" pulse and will report an error. The command station also will not be able to read the decoder without the resistor. The decoder communicates to the command station by pulsing the motor to cause a momentary increase in current consumption(the acknowledgement pulse), and with no motor or resistor, there is no increase in current for the command station to detect. What some people will do is temporarily install a resistor for programming, but remove it for operation so that they do not have to worry about it getting hot during operation.

    Note that the presence or absence of a resistor will have no affect on Ops mode programming because the command station does not look for the acknowledgement pulse during Ops mode programming.

    Digitrax makes one (SFX0416) that might be useable in Z scale.
  11. zscaler

    zscaler TrainBoard Member

    I found the secret to make a Z scale engine louder. Well, the car NEXT to the engine.

    More speakers!

    I put three speakers wired in parallel into the shell of a B unit in a AB F-7 consist. Wow, is it loud!
    You will love it Mike!

    The three speakers and decoder will fit into the B unit shell. The Marklin B units are easy to modify to add room. Well some metal removal is required - still working on that part.
  12. Cleantex

    Cleantex TrainBoard Member

    The most important in speakers is to have an in volume adapted resonance box.
    The size of the speaker is less important. If you compare with a residential stereo installation
    you understand what I mean.
  13. Svein-Martin Holt

    Svein-Martin Holt TrainBoard Member

    Will the decoder work with so low impedance? The spec says the decoder should use 4ohm speaker, with 3 pc 4 ohm speakers in parallel the impedance will be below 2ohm and that may destroy the decoder, may be, or?
  14. zscaler

    zscaler TrainBoard Member

    These are 8 ohm speakers. That should help. Anyone know if there is a problem with 3 (or 4) speakers connected in parallel?
    I had the decoder connected to the speakers and was "starting the engine" (nice start up sound) and "running the engine", "revving the engine" while honling the horn and ringing the bell - all at the same time. I believe the decoder has 8 possible channels. Should we check with ESU about this?
  15. rray

    rray Staff Member TrainBoard Supporter

    One 8 ohm speaker is 8 ohms, 2 in parallel makes 4 ohms impedance, 3 in parallel is 2.67 ohms, and 4 in parallel is 2 ohms.

    If you put 2 in series, you get 16 ohms, and another series of 2 in parallel with the first 2 gets you back to 8 ohms impedance.
  16. zscaler

    zscaler TrainBoard Member

    Thanks Robert!
  17. zscaler

    zscaler TrainBoard Member

    ESU 73800 series decoders use "4 or 8 ohms".
  18. Loren

    Loren TrainBoard Supporter

    Pardon the pun David, but this all 'sounds' very exciting. So when do we get to view a video of your F7 noise makers?
  19. up mike

    up mike TrainBoard Member

    You Go David!! and Yes we need a new video.......
  20. eit27

    eit27 TrainBoard Member

    Here is different approach to what David has already created. Using the same component as David has used, with the exception of adding power pick-up to the trucks of the boxcar itself. This is a complete stand alone unit that can be used with an loco. Assign the boxcar its own unique address and consist it with another loco.

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