xlr vs rca

Lewn,

Also, in any "balanced" design, an early stage, have to split the signal into positive and negative halves?

A phono cartridge can output a differential signal and most if not all modern DAC chips have differential outputs so no split is needed. It can start out that way.

I am just not aware of any other way to do it with tubes

you simply build 2 amplifiers in one chassis like stated earlier and one amplifies the + signal and one amplifies the minus. I don't know how all of the balanced manufacturers approach the problem but you can certainly do it that way. I did look through BAT's website and they make no mention of differential circuits. Perhaps they use them but don't talk about it?

Shadorne,

I'm afraid I don't follow. The balanced builders are just as likely to use gold plated connectors as the SE crowd. As for ground loops, take a look at my system. The phono is balanced into the pro box but it is converted to SE by transformers at the output of that box and is SE from then on. I run 107dB efficient horns with SET tube amps and even with the phono turned up I have to my ear up near the speakers to hear any kind of noise. No hum, no ground loops and I am biamping.

Thank you all very much. I have learned a great deal from studying all of the input I have been given.

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.