the sound of the interconnect won't be a thing
Malarkey!
Assuming balanced circuitry and connections are properly implemented, which far too often they are not, they can reduce common mode noise. FULL STOP.
For
balanced interconnects to be immune to cable, they would have to be
immune to the laws of physics. Balanced lines [and connectors] have
impedance and impedance controls frequency response.
Regarding the full stop, internally in a true balanced circuit in addition to improving CMRR, you can also improve power supply immunity, and since CMRR can be high, you get insensitivity to ground noise.
Actually, the way the interconnects become "immune to cable" (sic) is through two mechanisms, all according to the laws of physics. The first is that the balanced system is low impedance- at 1000 ohms (or 600) the impedances are so low that the capacitance and inductance of the cable are swamped and become negligible- and thus inaudible. The second is that the signal is not sent as a ground return through the shield. If you violate either of these tenants, the cable becomes audible. This is easy to prove through both measurement and audition.
differential amps tend to be lower noise we don't need as much gain stages to get the job done
If number of stages is a criteria, use a transformer. Differential amps per se are all over the map in terms of gain vs noise. The devil is in the details.
Transformers limit bandwidth and make distortion. Without them the circuit is noticeably more transparent. We've been doing balanced line longer than anyone else in high end audio; don't think we haven't tried transformers, and of course we are known for being transformerless :)
the other reason for balanced lines is elimination of ground loop noise
I'll
wager that 6 9's of 'balanced' home audiophile systems do not lift the
shield at the destination. Depending on amplifier design, there may be ZERO ground loop improvement over an unbalanced system.
In a balanced line system there is no need to lift the ground at one end of the cable. You are correct about the amplifier design issue; IME/IMO many high end manufacturers don't understand grounding and don't understand how balanced lines work either.
The balanced line system was created to get rid of interconnect cable colorations
The
balanced line system was invented by the telephone company to increase
noise immunity and power transfer over long distances. Nominally 600Ω, but at 1 frequency ONLY! Low frequency performance is abysmal.The 'telephone sound' is a direct result of balanced cables.
:) of course noise isn't a cable artifact, but you forgot to mention the loss of high frequencies, which made transcontinental phone calls impossible prior to balanced lines. If loss of highs is not a coloration, what is?? Yes, the phone company did just that, and the idea was quickly adapted by the recording industry as running microphone signals over a long distances was a similar problem. Through the ability to transfer power the system swamps cable capacitance and inductance (both of which cause interconnect cable coloration). This is the low impedance aspect to which I referred earlier. Our balanced preamps feature miniature power amps as their line sections- they can make a little power.
Many balanced devices are bodged to accommodate unbalanced operation and
coupled with generally incorrect balanced wiring, they don't stand a
snowballs chance of optimum operation in unbalanced mode.
If 4+ decades in electronics has taught me anything, it's that if it can be screwed up it will be: - inexperienced engineers
- incompetent sales staff
- ignorant consumers
This has been a beef of mine for decades, but just because this is so does not mean that all balanced line products have these issues.
I should have said "Use caution if driving an unbalanced amplifier from the balanced outputs."
We run into that problem too. What most people don't understand is that balanced and single-ended operation is inherently incompatible; you can't have 'quasi balanced' or any such nonsense. Either its balanced, or in the case above, unbalanced. In our preamps, since the output floats with respect to ground (no signal return current in the ground) if you attempt to use only one of the signal pins (ex.: pin 2) and ground (pin 1) you will get a buzz. This is because pin 1 has no direct connection to the return circuit of pin 2 and so pin 2 acts like an antenna. To correct this, pin 3 in this situation has to be also tied to ground (and because our output floats, this can be done without damage) to prevent the buzz. But of course then the output of the preamp is single ended, no longer balanced.
