A few points, Greg.
First, how long do the Keep Alives provide power to the board? Keep Alives are designed to carry a locomotive over dirty track or switches where contact is intermittent. They’re not long-term back-up power. Most users I’ve chatted with don’t want more than 1 or 2 seconds of stored power because of the risk to scenery in the event of a derailment where the loco leaves the track and keeps going. Unlike deadrail, if a Keep-Alive-equipped loco leaves the track and keeps going, it’s not receiving the “stop NOW, dammit!!!” command from the controller, and will cheerfully continue tearing up the plaster and ground foam until such time as the Keep Alive fully discharges. You don’t want more than a second or two at the most capacity in that situation. That will be fine for quick interruptions when changing direction in an analog DC environment, but it requires you to get moving immediately again to avoid the sound dropping out. If you’re switching cars, it’s not uncommon to be stopped for 30 seconds while coupling/uncoupling and throwing switches. That’s going to drain even a high-capacity Keep Alive.
Second, yes, you can set the throttle to “minimum” voltage to keep the sound going but the motor stopped when pausing for more than just a few seconds (the life of the Keep Alive). That requires you to have a controller where you have a visual representation of the voltage going to the track (knob, slider, meter, etc.). How do you do that on systems that use pushbuttons, like the Old-school Train Engineer, Railboss, or similar systems? There are many modelers who love the simplicity of “button one makes the train go faster, button two makes it go slower.”
Third, “Keep Alives” are not easily fitted to every DCC decoder. This is less of an issue as new decoders are developed and that feature becomes more and more “standard,” but it’s something to think about. Also, Keep Alives add to the cost of the decoder, so if you’re comparing dollars for dollars, it’s a line item in the equation.
Fourth, track voltages. Large scale power supplies have been known to put out upwards of 30 volts to the track. Many HO decoders aren’t going to like that very much. “Hey, that’s a great smoke unit!” “Nope, that’s my DCC decoder that just got nuked.”
Fifth, even if your decoder will handle your track voltages, how do you deal with PWM incompatibility? While it’s easy to say “just filter your track,” that works on only your track. What happens when you take your trains to run on someone else’s railroad or club display that uses PWM? You’re certainly not going to put a filter onboard every loco.
Sixth, many “critter” type locos I’ve encountered are direct-to-motor wiring from the rails, often in very tight spaces. All things being equal, what’s the easier installation? Two wires soldered to the existing track pick-ups, or having to break the connection between the track pick-ups and the motor to do a full-on DCC installation?
Of course you can use HO DCC decoders in an analog environment if you want inexpensive sound. No one here is suggesting otherwise. However, there are many factors which historically have, and will continue to throw roadblocks in front of this practice finding widespread use–certainly to any level where they may be considered “competition” to a standalone sound system developed specifically for analog DC. If DCC in analog DC works for you, great. Run with it. Don’t expect to find a crowd of people running behind you. The letters “DCC” scare the bejeezus out of many folks, and even if it were “Plug-and-play” simple, they’d run the other direction.
Later,
K
