Hi Folks
Like most things in life balanced lines have an up side and a downside.
Balanced lines solve a problem of noise pickup in the cables. Cables are antennas to the outside world and any RF or electromagnetic energy striking the cable can be amplifier in a 2 conductor RCA style cable by the system adding noise. Balance lines have 3 conductors and one of them is shunted to ground so any RF etc. hittiing the cable is cancelled due to a process called 'common mode noise reduction'. The longer the cable the more potential for pickup there is.
So in lengths longer than a meter I usually recommend using balanced lines. With shorter lengths it is not as critical.
Now the downside of Balanced lines - you need to have 2 more circuits in the signal path for a balanced line to work so it could be argued that those extra circuits can cause deterioration of the signal. Balanced lines can be done in a number of different ways - transformers or IC's or as we do it with 'Discrete Class A' circuits in order to minimize their contribution of complexity to the signal path.
Hope this helps.
james
