Metadyneman wrote: ... The original 36-557 was a re badged Soundtraxx decoder and was awful! ...
Incidentally my Bachmann "Killarney" (which I have re worked as City of Truro) has a 36-554 in it and is and excellent runner at all speeds.
I had one of those Bachmann badged Soundtraxx decoders supplied by a friend for installation with his Bachmann O4 2-8-0, and it was very jerky and 'granular' plus whiny sound effects, a 21 pin Lenz Silver delivered the required refined and silent running. Subsequently same friend wanted his latest purchase - Bachmann J11 - decoder fitted, and the laid aside Soundtraxx was given a try. I had to use one of the speed curves with the biggest inflexion to get the reasonably linear speed progression my friend wanted, but the motor control was smooth and silent. Later we switched it into the O4 and there was all gnarly performance again. Both models had all the suppression components stripped out, and ran equally sweetly on resistance controller DC before DCC decoder fitting, and had very similar looking motors and drive lines. Got to be something variable in the motor characteristics to produce such different interaction, I suspect a resonance of some sort.
By no means the only example of a decoder 'good in this model, poor in another', with both model mechanisms of outwardly similar construction and DC performance.