6" This is false, your either hearing things or your biased toward your own retail preamp product.I certainly do hear things :)
In many cd players or dacs I've seen the balanced output is just an added opamp changing the "real' single ended circuit to balanced. Same goes with the input of many poweramps, which btw are single ended output to the speakers.
The only time balanced is better from source to to pre, or pre to power is for noise cancellation with interconnect over 5mts>
George, one thing you will see me harping about a lot is that a lot of high end manufacturers don't support the balanced standard, or for that matter don't seem to know that such a standard exists.
You seem to be one of them. The standard is defined in the AES File 48. Here are the basic aspects of balanced line operation, going back to the 1950s:
1) the operation is low impedance, in particular the source
2) the signal occurs with respect to its opposite, rather than ground (IOW the non-inverted and inverted phases); ground is ignored and is only used for shielding- no signal currents are in the ground connection!
3) pin 1 is ground, pins 2 and 3 carry the signal (neither is 'hot' or 'cold'). In the US, pin 2 is non-inverting.
If the device used does not support the standard, you may not get all the advantages that balanced operation offers. Off the top of my head, this is one reason I don't recommend passive volume control systems, since I can't think of a way they can be set up to support the standard; see points 1 and 2 above (a TVC could do it, but I've yet to see a TVC that had all the loading issues solved and didn't color the sound).
As a result, with a passive you still have to audition the cable in the resulting system, and the whole point of balanced line is that you **don't** have to audition the cable, because its simply going to work right and sound right, 6" or 30 feet no difference.
Now to address some other misunderstandings you have in your statement above, many DACs fly in the face of your comments about their internal construction, for example MSB, where the internal construction often includes more than one DAC, running out of phase. But more to the point, the reason to go balanced and whether you can do it properly has nothing to do with the internal circuit and has everything to do with how that circuit talks to the outside world. An example is the old Ampex 351 tape machine, which uses input and output transformers to do that job. Audio Note made a DAC that operated in a similar fashion. IOW if you have an entirely single-ended circuit which drives an interface that properly supports the standard, the result is that you don't have problems with the interconnect cables.
Although our circuits are entirely internally balanced differential, that isn't needed if the circuit simply has the right interface (there are benefits from balanced differential operation of the circuit, but that's another conversation). From your post, it seems you don't understand what that's about.
I've always thought that audiophiles would jump at the opportunity balanced represents. I've heard interconnect cables make a night and day improvement in a system; many audiophiles have. When you run balanced, the cables no longer editorialize (and you get lower noise). I've seen a set of $200 30 foot cables beat out a set of 20 foot cables that were $1000/ foot, so this can be pretty significant.
Your comment about amplifiers is also false- I don't have to go very far to prove that; the amps we make are balanced all the way to the loudspeakers and I can name quite a few more- the GAS, BAT, any amplifier that is bridged, any tube amp running zero feedback.