Originally Posted by
Tyll Hertsens 
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Originally Posted by gpalmer
The amplifiers running around at the 1K level are already very, very good. Going balanced at this point is in my experience, the best way to improve the sound quality, it offers the largest chunk of improvement that I've heard at that level.
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I want to echo gpalmers sentiment here: As you go up and up with a traditional unbalanced amp, especially once you get above $1K (not including DACs and such) you begin to be pretty hard up against the diminishing returns curve, so doubling your price gats you only a few percentage points of sonic performance improvement. But doubling the price with adding (effectively) double the electronics of a balanced amp seemingly DOUBLES the performance, which is a damn good deal when your normally so hard against the diminishing returns curve. That "doubling" of performance may be an overstatement, but it's pretty clear, to any one that has heard it, that something very special happens with balanced amps that would be very hard to get any other way.
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Originally Posted by iomusic
actually it is for public broadcasting such as a concert , because the signal transmits long distance,the cable is hundreds feet long.
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Balanced transmittion lines is a similar thing but really not the issue here. Using balanced trasmition line schemes can dramatically reduce common-mode interference on audio transmittion (and many other things like telephone lines) over distance, but it is not really the issue here. Balanced mono-block power amplifiers for speakers is a more direct analogy, and has long been done in the speaker world for similar improvements in the higher end of that spectrum of product. When we came out with the BlockHead (the first commercially available balanced headphone amp) our intention was to exactly mimic the balance mono-block paradigm of the high-end audio world. At first we did it simply because we wanted to make a rediculously expensive headphone amp that the broad audiophile audience would understand. After listening, we were gald we did, as the improvement is truly dramatic.
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Originally Posted by gpalmer
The situation is less clear in the tube world,
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I'm pretty sure this subject hasn't been explored here fully, and I have some serious concerns with tube balanced amps. Here's why:
Much of the gloriousness of a tube sound is the second harmonic distortion content of the drive signal. (This gets a bit technical, so I hope you can follow along without a bunch of diagrams and pre-existing technical understanding. Sorry if this isn't clear to many.) Second order distortion comes from a monotonic transfer function of the amplifier. That means that the gain curve of the amp is a simple curve shape that is characteristic of a single ended tube amp. There are push/pull tube amps that reduce or make partly "s" shaped this transfer function, but in my view it is the pure single ended tube amps that are the real winners in term of delivering that "something special" of tube amps. For example the magic of a 300B SE amp would largely be lost if using 300B tubes in a push-pull design. Now imagin that you have 2 300B SE tube amps driving headphones in a balanced configureation. What would happen is that you effectively make the two SE tube amps into one 300B push-pull amp with the headphone driver in the middle. The two monotonic transfer function curves that give you that sweet SE sound now cancel each other, to some degree, and you are left effectively a sum transfer function that is symetrical. A symetrical transfer function give you odd-order harmonic distortions not even-order harmonic distortions. Disclaimer: This is just an educated guess on my part and I would love to hear from some of the tube designers how desirable even-order distortions could be retained in a balanced configuration.
(Please ignore that last paragraph if it just served to confuse the crap out of you.)
Bottom line: get yourself to a meet where you can hear a good balanced amp, and you know what the heck we're so jazzed about.
