@FrankfordJunction Ron L,
I'm glad you started this topic. I've been meaning to work on mine to make it sound better, but haven't made it a priority, until today when I placed a parts order.
I've been leaving the sound switched off, because I don't like the slightly distorted (overdriven) sound it has or its loud volume. But I would like to have it make the sounds it supposed to have if they were tamed a bit.
So, I just ordered a 1K ohm logarithmic taper potentiometer (variable resistor) that I plan to wire into the speaker circuit on mine. I'm planning to have the adjustment shaft end accessible from underneath, just flush with the bottom of the frame so you don't see it.
By limiting the output current from the audio amplifier, it may sound better. It will definitely be quieter and I will finally be able to adjust the volume and hopefully enjoy the locomotive's "operational" sounds.