I have a Spectrum 4-4-0, item number 83409, which is about five years old, perhaps a bit newer.  Bachmann does not recognize it in its on-line catalogue now.  It came with a very limited DCC decoder installed.  Recently I find that it seems to have lost its slow switching speed in either direction.  I do not know of any way to adjust the starting voltage, or to change any of the other possible CVs.
Does this decoder have any capacity to have its CVs changed?  Does it have any CVs or other capacities other than to control the head light, speed and direction in any case?
I am thinking of installing a Soundtrax decoder with sound.  Is that just the best action?
Thanks.