Pretty sure this is a setting you can only change via DCS, so if you know someone with a DCS system, or your LHS has one, you can set it there.
Here is a document from Ulrich Models that explaisn what you can and cannot do with MTH locos in DCC: http://www.ulrichmodels.com/prostores/DCC_Topics/MTH_DCS_and_DCC.pdf
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I own six MTH HO scale SD70Ace locomotives, along with several other steam MTH units. I operate a Digitrax DCC "Super Chief" system, and use these locomotives in consists which works well, pulling 100 car trains! My question is, can the sound volume level be "locked" at maximum? After shutting down the system, when I re-start, the volume levels of these locomotives is low and must be increased by using the F6 key on each unit address. Maybe they default to low volume. Perhaps there's a CV value that can be set to maintain maximum volume. I know MTH doesn't support a lot of CV programming. Any suggestions?