xlr vs rca

No hum, no ground loops and I am biamping.

Ground loops do not always show up as hum with volume turned way up with no music playing (of course really bad ground loops do). The insidious kind is when a power supply leakage affects ground on a device which adds modulated noise on your cabling as a function of power demands. The way to reduce this is to go balanced (so that the ground loop is induced equally in both positive and negative signals). You really can't detect this kind of insidious effect other than to observe the improved clarity of going to a properly balanced setup where grounds from different components are much less likely to get to your signal. The effect can of course be small when comparing good equipment that is well matched... nevertheless, several DB in better noise floor can usually be expected with XLR.

the ground loop is induced equally in both positive and negative signals

Balanced circuits are better at rejecting any noise from the power supply but your description of it doesn't make any sense. It isn't a ground loop problem.

When using truly balanced interconnects, i.e., differential signals on pins 2 and 3 and ground on pin 1, I’ve found it’s very often advantageous to float the ground at one end of the signal path. This can be easily done by disconnecting the ground on pin 1 at one end, and only one end, of the cable.

The result is that the cable is still shielded but there is no electrical connection between the chassis grounds of the equipment. This not only increases hum isolation but also prevents high frequency digital clocks and switching power supply noise from traveling between chassis.

I’ve used this floating ground scheme on large analog post production installations (with lots of patch bays and signal routers) as well as on my AES/EBU balanced digital audio cables at home.

On a separate note, while balanced interconnects have way better noise immunity than unbalanced it’s not free: they require twice as much circuitry in the signal path and both sides of a balanced circuit must be perfectly matched.

I’ve found it’s very often advantageous to float the ground at one end of the signal path.

Agreed that is often the first thing to try out....it stops the microamp ground loop currents flowing between the various chassis as well as still grounding the shield to give you better RF protection.

Balanced circuits are better at rejecting any noise from the power supply but your description of it doesn't make any sense. It isn't a ground loop problem.

You need to read up on what Whitlock says about the reasons why XLR balanced is so important for ground loops. Think about how a power supply fluctuates under heavy demand and how this may affect microampere ground loops between gear (the BIGGEST problem in audio as RF noise pick up on analog audio is much less common). Then realize that ONLY ONE wire in in an RCA circuit will carry this current flow on your signal wires - IT CANNOT CANCEL (as it does in well built XLR gear and cabling).

=> this is why a BIG BEEFY power supply is NOT simply about more power...often it can be more important for how much cleaner the backgroud or canvas upon which the music plays can become...

Perhaps I was not clear in the last post.....a BIG BEEFY power supply means less fluctuations due too the varying demand from dynamic music and therefore less ground loops from leakage to ground from the PS => less noise induced into the low level analog signals between components.