Since then I've wanted to ask the obvious question -- why don't all
manufacturers who produce preamps with fully balanced designs adhere to
the standard? Is there a downside or trade offs to doing so? I've been
scratching my head over this one for a while since it doesn't seem like
it costs much more to adhere to the standard, especially if you're
going to the trouble and expense of building a fully balanced unit from
input to output. What gives???
@soix The problem is that its not easy to do. So most manufacturers just don't.
With power amps its pretty easy to support the standard, but with preamps its hard. This is because of the requirement to float both the inverted and non-inverted aspects of the signal. There aren't many ways to do that! In the old days when tubes were the only game in town, it was done with output transformers whose secondary (the output side of the transformer) was meant to drive a 600 ohm load. That satisfied the floating requirement and also the low impedance requirement.
When solid state came along things didn't change much in this regard, mostly due to the requirement to float the balanced signal. So in the recording/pro audio world, there are still a lot of products that have output transformers even though they are solid state.
Transformers of this type have much wider bandwidth than output transformers do on power amps, so they can be much more transparent! Most LPs and CDs in your library had a transformer somewhere in the recording signal chain. But such transformers cost something, although to anyone in high end audio, really not that much. You can use line transformers (for a few hundred dollars) with conventional single-ended preamps with excellent results if you set things up right, and have all the advantages that balanced line cables have.
So the biggest single 'short hand' that manufacturers use to cut corners is to dispense with the floating aspect of the signal; most are in the business to make money more than they are to see how far they can push the art, so adding an output transformer is often seen as an extravagance that eats into the bottom line. They may also think that the transformer is less transparent, and if it were only in that regard I agree, but if the cable starts to introduce a coloration or lack of focus or the like, maybe that's not so true.
The only other way to do it where ground is ignored is the way that we do it, which involves a circuit called a Circlotron. This allows for a direct-coupled balanced output that is floating with respect to ground. I think the problem here is that to do this right, you have to get a lot of things right from one end to the other, and to make matters worse for other manufacturers, my company controls the patent on this process.
So the competition has to use output transformers, infringe our patent, or just not support the standard. The problem with the latter is the baby with the bath thing; if you ignore too many aspects of the standard you also lose a lot of the advantages it brings.
I've always seen the cost of high end cables as a hidden cost of any single-ended preamp- in some cases I've seen them cost more than the preamp! Balanced preamps don't seem to cost any more than their single-ended competition in practice (although in our case we price according to a formula and most companies price to what the market will bear, so our gear tends to be less expensive), so the advantage of not having to buy expensive cables to make it all work would *seem* to be an advantage. But in 29 years of making balanced preamps, my experience is that most audiophiles don't care about the cost of the cables- I totally got that wrong.
