I am curious about your choice of the MTH PS1 AA-0000011 smoke unit. Apparently these are $50+ each...and you're planning on 4 units? Can you share the application - presumably this is NOT for installation in an engine or rolling stock?
So here's the thing. While you can indeed hook it to a DC power supply, the PS1 smoke unit has a clever voltage regulator circuit - considering it was designed in the last century.
There are 2 smoke heater resistors. The on-board circuit uses the track voltage to "decide" whether to use one or both resistors. The circuit has been posted and discussed many times in previous OGR threads and I suppose we can re-visit the component-level nitty-gritty if need be.
The upshot is you may find that when operating with DC voltage, there is a range of voltage where you get LESS smoke as you increase voltage! And the behavior will be different between AC and DC. So, for example, it could be that going from 12 to 15V AC increases smoke to your requirements, but that same increase from 12V to 15V DC produces less smoke!
So back to my original question about how committed you are to using the AA-0000011.
There are other fan-driven MTH (and others) smoke units that don't have the PS1 regulator circuit and instead give you direct connection to the smoke heater resistors. In which case more voltage will guarantee more smoke - and 15V AC will produce the same amount of smoke as 15V DC.
Apparently you got/bought a new PS1 smoke unit...but if you already had the 4 units I'd consider modifying this voltage regulator part of the circuit to give direct access to the heater resistors. It can be a messy affair, cutting wires or circuit board traces, soldering, etc..
