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Several of my engines are DCC and my wife bought an NCE Power Cab for my Christmas present. The rest of my engines are DC. I have two main lines and thought I could run one on DCC, and the other one on DC. Has anyone else done this? It'd be cheaper than installing decoders in all of my engines.
If its a small layout or test track, yeah, a DPDT switch can do the job. (see October 08 RMC for my article on this exact thing) but looking at the site you have linked to and the way your layout is growing and maybe needing boosters or being split into diferent power districts, I would advise against it.
DCC systems do not like being fed DC current. They let out a lot of smoke and stop working (Trust me, I know) Even a breif accidental voltage feed is disaterous. Decoders are pretty cheap, relay controls, additional wiring and secure lockouts to keep the dc and dcc system separate are a pain in the butt. Its just so much easier to add decoders and be done with it.
Just pop the top off and wire it up from there! Note, It's not plug-n-play and Bachmann wiring is never the right colors. Gotta double check em with a meter!