Bass shaker disconnects when motion starts

Im using a 3dof rig, with SMC3 soft, as soon as motion starts in game, shakers goes off, but if i totaly stop the cars, shakers turn on again, this thing happens at the point they goes off permanently, and says connection error.

Running bst1 theres a nobsound amp, but connected trough an 3.5mm jack, because built in sound card of the amplifier died. 

thinking it was a power related issue, change psu to the amp, but nothing changed.

i think its something related to communication. tried with a Hub, and direct to an usb port back on mobo, getting same results.

Sometimes works, but for example, engine vibrations, stops for a second, and start again. a huge crash also stop them

dont know what to do.