Now, with all that aside, if we look at cable construction - unbalanced/RCA often times looks to have an advantage. For example many or most XLR cables, even the high end, funnel the signal through a $4 Neutrik XLR connector. This can be a limiting factor as they are usually silver plated brass, or lower grade copper. The better Furutech XLR connectors may still be using impure copper like OFC, instead of OCC. So, this will add distortion compared to the cream of the crop RCA connectors such as those from WBT. And it's audible (I've experimented a lot with my handy soldering iron). Lastly, it has been demonstrated that balanced designs cancel even order harmonics (which we associate with a pleasant listening experience), but do not cancel odd order harmonics (which we associate with a displeasing listening experience). Your mileage may vary but these are reasons why, anecdotally, folks may observe less sound variance from cable to cable with balanced designs than with unbalanced designs.
I, myself, will always use single ended so long as I'm using a tonearm which is wired single ended (as is my Kuzma 4-Point). I simply do not believe in converting unbalanced to balanced (nor the other direction) midstream. And I actually think the best answer to the question is to avoid doing so in any system where transparency is a primary consideration: If your source is balanced, stay balanced throughout. Similarly, if your source is unbalanced, stay unbalanced throughout the chain.
It might be of interest to you to know that all cartridges are balanced sources, and only get to be single-ended by how they are connected at the output of the tone arm. If you have a five wire connection (the 5th being the tone arm ground) then you have a balanced connection- often which is being run single-ended. The nice thing about going balanced with the cartridge is that the tone arm cable ceases to impose a sonic artifact, and since this is at the output of the cartridge, this is the best possible place for that sort of thing to be going on.
As mentioned previously, there are a lot of balanced output drivers on components out there that use 100% solid state. To get a truly balanced signal, one needs a transformer, Why? because the signals on the + and - wires will never be EXACTLY the same amplitude with solid state. This creates an imbalance in the two signals which wreaks havoc with the input receiver.
Devices like this will eliminate this imbalance. It is not cheaply done at high sound quality:
http://www.empiricalaudio.com/products/final-drive
As for the cable itself, there is no reason why one cannot fabricate an XLR terminated balanced cable that performs just as good as a single-ended RCA terminated cable. Optimization of both cables includes: proper selection and treatment of the conductors, geometry that minimizes capacitance per unit length and dielectrics that minimize dielectric absorption.
Steve N.
Empirical Audio
Just so you know, you can have a truly balanced output without using transformers. You can use a Circlotron, which also allows for the balanced output to be direct-coupled. We got the patent on that. FWIW, we introduced the first balanced line components to high end audio.
50 foot is the standard, not 25.
This statement is false. There is no standard for interconnect cable length
All else being equal I prefer single-ended connections. I do not like that balanced connections suppress even order harmonic distortion.
Ron, as pointed out earlier the cable has nothing to do with suppressing even ordered harmonics. The operation of the source and load does, but there is more to that and I suspect you want to know about it. The reason people often think single ended is better has to do with distortion- particularly the even orders; if you're going to have distortion, why not have distortion that is musical? But its not that simple, quite often with high THD you also have higher IMD, that of which is extremely audible and irritating.
In a fully differential balanced circuit, the primary harmonic distortion component is the 3rd rather than the 2nd. The 3rd harmonic is musical to the human ear in a way that is very much like the 2nd. Now you might know that our circuits are zero feedback and fully differential and balanced. We get the 3rd harmonic, but at a level that is less than the the level that the 3rd shows up in single-ended zero feedback circuits. The other, higher ordered harmonics are also at a reduced level.
Something you may not be taking into account is that when distortion of all harmonics is present in a gain stage, as the signal progresses from one stage to another, those distortions are compounded. If you can keep distortion down as the signal proceeds through the circuit, overall you will simply get less of the most irritating distortions- the higher ordered harmonics and IMD.
Now the ear has a masking principle that is well-known. The presence of distortion can mask lower level detail that is otherwise heard when the distortion is controlled. So a fully differential balanced circuit with balanced connections can sound considerably more transparent and more relaxed than its single-ended competition, and this difference is not subtle- its something anyone can hear in 5 seconds flat. I would not be so quick to discount balanced operation based on some bad apples.
By bad apples, I mean those players in the high end audio industry that don't seem to understand how balanced connections work, and thus make 'balanced' products that get really variable results. How its supposed to work is that the cable should not impose a sound quality, but we see that happening all the time, and its because many high end audio products don't support the balanced line standard (often AKA AES48).
In a nutshell, if you get to hear balanced line done right, there's no going back to single-ended. Its that good- imagine a system where you could have the sound of the most expensive and best cables on earth, but without the cost. That's the balanced line system- it was created in part to eliminate the sound that cables otherwise impose and as also created to get rid of ground loop buzz. Its very good at both if the standard is observed.
