Crimping Tools for Larger Gauge Wires

Looking for some guidance on reasonably priced but effective crimping tools and crimps for wire a few mm2 in cross section/8AWG and up, as I have a ground loop issue to resolve for the head unit/amp combo I have in my car. The frequency of the rogue whine varies with engine speed and its volume with the load on the system, so I think it's alternator related and I'm picking up a voltage offset between the chassis and engine earth points caused by the alternator current which becomes a signal included in the earth for the phono leads from the head unit to the amps. Want to rewire joining the amps, head unit and engine earth with something of a suitably meaty to resolve this.

Any pointers gratefully received, many thanks!

Steve.

You can get a really inexpensive hydraulic hex crimping tool from aliexpress or similar, usually comes in a yellow blow-molded plastic case. It's a pretty average piece of kit, but does a good job with some care taken.