Is this typical on pre and amps that have both Single Ended and Balanced Outputs?
@post2338 @cleeds
It really should not be that way, and this statement
A differentially balanced design will yield a 6dB higher output than it will single-ended.
Is false. But there is an important nuance/ caveat! The way balanced operation is supposed to work is that the signal travels in a twisted pair inside a shield, and the shield is only used for shielding (unlike in an RCA style cable where the shield is often part of the signal return).
In the old days and still to this day transformers are used to drive the balanced line cable. The transformer doing this is driven by the source (perhaps a preamp) and its output is a simple secondary winding without a center tap or any other complexity (so its output is exactly 2 wires). Its merely connected to pin 2 and pin 3 of the XLR connection. Pin 1 is ground and is not part of the transformer connection at all.
Now a transformer can drive single-ended as well as balanced. All you have to do is connect pin 3 to ground (pin 1 of the XLR) and the single ended connection is ready to go. But you may notice that the signal level has not changed at all- its still the same transformer with its same signal.
The reason you see this 6dB increase talked about so often is that the circuit driving the XLR output doesn't support the balanced standard, and is likely just two single-ended outputs that are operating out of phase with each other. So the single ended output is simply one of those phases (usually the pin 2 connection) and if you add the second phase for a balanced connection you double the voltage- and there is your 6dB.
That isn't how its supposed to work, but most high end audio companies with balanced line products either choose to ignore the balanced line standard or are ignorant of it. I don't know which. At any rate, when this '6dB thing' comes up, you know right away that the circuit isn't supporting the standard.
The standard has two outstanding attributes. The first is because it ignores ground, ground loops should not be able to occur. The second is the interconnect cable won't be able to have a 'sound' like audiophiles are so used to hearing with single-ended cables; it allows the system to be more neutral, more musical. Ground loops create noise and can buzz when severe; with that property lost it won't be as musical! The same is true of cable immunity.
So its a real shame IMO that the balanced standard gets short shrift in high end audio. Its also why you hear so many people talk about how single-ended might actually be better, which it isn't. Once you hear a balanced line system operate properly by supporting the standard, you never want to go back.
