How to wire sound only decoders?

[jwils1]

I'm installing Digitrax SFX0416 sound only decoders in both an Atlas H15/16-44
and a P2K GP9 II.

I will not be using any functions on the SFX0416, just sound. On the
Atlas can I just wire the red and black wires to the front track pickup
wires or do I need to also wire them to the rear pickup points?

On the P2K the existing black wires seem to go to both the front and
rear left track pickups. There is a red wire attaching to a screw on
the frame. Is this a case of where the right track pickups go through
the frame? Can I wire the decoder to just the front black pickup (which
is really easy to get to) and to the red wire where it attaches to the
frame?

The Atlas has the factory supplied DCC decoder and the P2K has an NCE
DCC decoder plugged in to the factory furnished plug.

What I'm wondering is....if I just connect to the front black and red
pickups, don't these pickups actually also connect to the rear pickups
internally through the decoder, so I'm essentially getting track
connection from all pickups?

[loathar]

I would say the more direct connections to the wheels, the better. I did a decoder in a Bach and only connected one power wire to the common frame. I had a lot of light flicker and stuttering this way. I rewired to all the wheel wipers and it work much better. Power interruptions to a sound decoder would probably cause you more grief than a motor/light only decoder would.