It's the DC output of the controller that's the fundamental problem. DCC decoder fitted locos will operate on DC supply to some extent (provided they are set 'DC enabled') but not necessarily that well, as you have seen. I couldn't recommend a DC system to get the best out of decoder fitted locos: a simple resistance controller works best, but it's very much second best compared to:
What you really need, which is a DCC system: that will run multiple locos as required, up to the specified current output of the system. And if that's ever exceeded, a booster can be added to supply additional current. What's more it will enable the performance characteristics of each decoder and mechanism combination to be set up exactly as you require. With a DC system you have no way to find out how the decoder is set up, or any means of changing that set up.
If you are prepared to spend on sound decoders, the one off purchase of a DCC system is a single spend to get the best from them. Look for a system that can address 28 functions, sound projects are becoming ever more ambitious in the number of selectable sound effects provided, and plenty of function outputs will be what you want.
What you really need, which is a DCC system: that will run multiple locos as required, up to the specified current output of the system. And if that's ever exceeded, a booster can be added to supply additional current. What's more it will enable the performance characteristics of each decoder and mechanism combination to be set up exactly as you require. With a DC system you have no way to find out how the decoder is set up, or any means of changing that set up.
If you are prepared to spend on sound decoders, the one off purchase of a DCC system is a single spend to get the best from them. Look for a system that can address 28 functions, sound projects are becoming ever more ambitious in the number of selectable sound effects provided, and plenty of function outputs will be what you want.