The amp remote line needs to power the tuner, ISTR this is around 100-200mA @ 12v. A decent amp will draw no more than ~5mA from the remote line as it will just turn a mosfet switch on.

The amp remote line is rated at 1A. It's fused with a resettable fuse, and the high-side driver that switches it is overcurrent/overtemperature protected too. Just try it and see if it works.

Hugo