Decoder Recommendation

I am not that familiar with sound decoders to give you much advice.   I have installed some sound only decoders along with motor decoders.   

As for the RC GP-9, I think it has a Pittman can motor.   I am familiar with this motor.   The weaver single motor drives for the FA, FB, GP38, and RS3 use the same motor I think or at least a similar model Pittman.   I find that these motor draw considerable current.   Mine seem to want about 1.7-2.5 amps running and stall out at more than 4 amps.   For this reason, I use NCE D408SR motor decoders with this motor.    I have tried some of the smaller HO decoders that are rated right at the edge for 2 amps running, and they have failed.    So my advice is you need a motor control decoder with over 2 amps capacity running under load and over 5 amps stall.    The NCE meets this requirement.    A sound and motor decoder should have similar specs.

I meant to say Red Caboose not Intermountain GP9 although I seen one kind respondent knew what I was saying.....

I put a NCE D408SR in a Red Caboose GP9 I had and it ran great for along time.

ncng

does this engine have one motor or two?  1.75 to 2 amps sounds like a lot for one motor.  Regardless,  I have the G gauge MRC diesel sound decoders in three of my diesels and 2 of them have 4 motors each.  It is rated at 5amps.  I am not a diesel person and can't tell you if the sound is right for the model but it sounds good to me.  More volume then you will ever need and great low speed control.  Micro mark has them at close put for $69.  I run my trains a lot and they have been in the locos August or so.  Some of the horns and bell sounds are kind of weird but there are many to choose from.  I have been using QSI titans in the steam engines which do not have the current appetite that the diesels have.   email to astarr78@msn.com