power: 1/0 awg to 4 awg or just 4awg?

using a single 5-channel amplifier (accepts up to 4 awg power): are there any cons to running 4 awg from the battery to the inline fuse holder (100a fuse) > 4 awg from the inline fuse holder to the amp? as opposed to 1/0 awg from the battery to the inline fuse holder (300a fuse) > 1/0 from the inline fuse holder to the distribution block > 4 awg from the distribution block (100a fuse) to the amp? the 12v battery is under the rear passenger seat, space is extremely limited. eliminating the distribution block would be great because it would save me several feet of wire (and save me trouble cutting into the foam of the rear seat to make the distribution block fit), but i want the best current flow possible.

4G has 2.5x the resistance of 0G, ie, 4G means an 82mV drop per meter pr 100A. (Hence probably ~1/4V for a typical install using 3m/10' of 4G at 100A.) IMO if there is no need for a DB then don't use it. It adds extra resistance and failure points. But if you do use 0G or 0/1G, use the smaller fuse. There is no need for the 300A fuse (ignoring the fuse voltage drop).

oldspark wrote: 4G has 2.5x the resistance of 0G, ie, 4G means an 82mV drop per meter pr 100A. (Hence probably ~1/4V for a typical install using 3m/10' of 4G at 100A.) IMO if there is no need for a DB then don't use it. It adds extra resistance and failure points. But if you do use 0G or 0/1G, use the smaller fuse. There is no need for the 300A fuse (ignoring the fuse voltage drop).

thanks for the response, i think i'd prefer to buy a new inline fuse holder and skip the distribution block. i haven't been able to find a digital 1/0 awg in / 4 awg out inline fuse holder, do you know where i can find one?

i may have been over-thinking this; no reason i can't just use the existing digital inline fuse holder w a 100a fuse? 1/0 awg wire in / 4 awg wire out, i just tested 4 awg in it, it felt very secure. any potential downside to using 4 awg wire in the port intended for 1/0 awg?

Use the same gauge in & out. Since the input wire must be short, there is little point having a heavier gauge input cable. A smaller gauge in a large hole merely means less contact area, hence more resistance. But that should be negligible overall except there the contact are is so small (or bad) that it heats up and flames, but usually the wire & receptacle gauge & metal is big enough to conduct such heat away. And all fuses are analog, ie just "fuses". There are sloblow & fast blow etc, but no "digital" fuses.

oldspark wrote: Use the same gauge in & out. Since the input wire must be short, there is little point having a heavier gauge input cable. A smaller gauge in a large hole merely means less contact area, hence more resistance. But that should be negligible overall except there the contact are is so small (or bad) that it heats up and flames, but usually the wire & receptacle gauge & metal is big enough to conduct such heat away. And all fuses are analog, ie just "fuses". There are sloblow & fast blow etc, but no "digital" fuses.

yeah, the run from the battery to the fuse will be no more than 10" or 12". i guess i'll be putting the inline fuse holder and distribution block on ebay (they were from my old car), as i look for a 4 awg in / 4 awg out inline fuse holder. i should have clarified, when i referred to the "digital inline fuse holder", i meant "inline fuse holder with digital display"; it had a ground wire and a voltage readout. thanks for your help