You're kidding, right? I am still burning in my new K 701s with their Black Dragon cables! I am guessing they have somewhere over 100 hours on them by now, maybe 120-or-so, but although they sound very good indeed I still don't feel they have fully settled down yet...

I find I am reaching for the K 701s much more than the HD650s since I got the pair with the Moon Audio cables, which has never been the case before (regardless of which cables I use with the HD650s, I think I am up to four now). Maybe I'll find time to write up some thoughts over the summer.

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The guys at www.head-fi.org are really big on balanced connections. I guess it makes some sense because so many of them are using crummy DACs that spew tons of RFI/EMI into the area right around the cans, but I don't find it to be an issue in my rig. My Woo Audio WA6 only has single ended connection, but my CDP to pre-amp is balanced and well shielded via a heavy chassis, so I'm doubting that I would gain much from going balanced on the headphone rig.

Dave,

You may be confusing balanced headphone drive with balanced interconnections. While related these are really two different things and the benefits of the former extend well beyond those of the latter. See here for a better description than I could manage.

I have heard the difference on both Sennies and AKGs and it is quite significant. In particular, I was immediately struck by the deeper bass the K 701s produce when driven in balanced mode.

So I am definitely planning to go balanced with my headphone rig. The only problem is that means I will need a new DAC as well as a new headphone amp (I am currently using a Grace m902 which contains both but is single ended-only). I am leaning towards the very tasty looking (and sounding) Rudistor amp, the DAC is a bit more of a problem. Hmmmm...

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Are you sure that the amps were of the same power and quality?

Yes, I have heard the same amp (same actual unit) driving the same cans (HD650s, same actual pair) through two lengths of the same type of cable, one balanced and one S-E. At the same listening session I compared balanced and S-E AKG K 701s, although the balanced and S-E cables were of different types so this was not an apples-to-apples comparison.

The improvements in balanced mode were not subtle, as best I could tell entirely for the better, and quite similar in nature for both pairs of cans. The bass seemed deeper and weightier, and both transparency (detail) and dynamics seemed improved. For some reason the improvements to the K 701s seemed greater in magnitude than those to the HD650s, at least it made a much stronger impression. Whether this was because the difference was actually bigger (the S-E cable was the standard stock cable so maybe the baseline was lower?) or whether it just seemed so because the sound was more to my taste I will never know.

In fact the sound with the AKG K 701s driven balanced with Moon Audio Black Dragon by a Rudistor RPX-100 was the best I have ever heard through cans by some margin. I got that feeling you get when you instantly know what your next upgrade is going to be. I'm afraid you will have to take my word for this for now but I would strongly urge you to get along to a canjam and listen for yourselves.

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That said, perhaps headphones benefit from balanced operation differently than speakers for example.

There is at least one big difference. Stereo speakers do not generally share a common return path whereas S-E cans generally do. This inexorably leads to crosstalk and distortion. Of course whether this explains the perceived improvements in SQ is an entirely different question, however there is a difference.

Dave,

I believe the "common return" is one wire in most stock cables, although I haven't dissected them to check! However I assume some (maybe most) aftermarket cables have separate return wires joined at the plug, since most of them are offered as balanced or SE with only the termination differing. This approach is valid since unlike the case of balanced interconnects it is not critical that the wire offers a specific characteristic impedance within a close tolerance band.

I will leave the religion to the preachers, but adherents of balanced drive maintain that it offers sonic benefits disproportionate (in a positive way!) to the increase in cost. This is of course virtually impossible to prove empirically one way or another. I would very much like to compare the Rudistor RPX-100 that so impressed me with a good SE headphone amp of comparable price, for instance one of Ray Samuels' models or a Single Power, but all the likely contendahs lack representation over here so they are extremely rare.

Comparing half the Rudistor (which is effectively what you are doing when you run it SE) with the full monty balanced output has certainly convinced me, however I will probably never convince you and I'm not trying. I subscribe to some audio religions and not to others, however I usually find that 'epiphanies' are caused by memorable listening experiences rather than bulletin board discussions I can only recommend you listen for yourself if you get the chance.

I have pondered it on-and-off and I have not come up with a test that would really be apples-to-apples. The test that eliminates most variables is to compare the balanced and SE modes of an amp offering both, as I did, however in this case you are only using half the amp in SE mode.

I agree, head-fi.org has more than its fair share of 'Audio Taliban', although I still enjoy poking around there. It is unbeatable for tips on new headphone product releases and tweaks and you just can't beat the passion. There are more new threads in a day there than the headphone board here gets in a year!

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I have no idea what they're talking about, even after that thoughtful link in this thread.

Dave,

It's really simple but I'm struggling to come up with a good analogy. Try this. Imagine a rope going over a pulley. One person can pull on the rope on one side of the pulley ('live') and the rope the other side just follows along ('return'). In the equivalent of balanced mode two people pull on the rope in unison (i.e. in different directions relative to the pulley) on either side of the pulley. The 'return' leg is now being actively driven by a signal 180 deg out of phase with the first one.

How did I do?

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Still, if the amp is well designed with a properly designed ground, I don't see where balanced will do any good, if all it does is have two routes to ground rather than one then that seems inconsequential. It's not like the difference between a balanced IC vs. single-ended, it's merely changing the point where the two grounds become common.

This is indeed getting quite confusing but I'm not quite sure why!

In a fully balanced configuration neither live nor return is tied to ground, indeed the very definition of 'balanced' is that both signals have the same impedance with respect to ground. In practice the ground 'floats' half way between the live and return signals. This is true whether you are talking about a balanced cable (neither pin 2 or 3 is shorted to pin 1 which is chassis ground) or balanced drive in which both the live and return signals are amplified completely independently. So what is being described as 'fully balanced' is indeed fully balanced, both live and return are being independently and actively driven by output stages referencing the same ground.

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As for "fully" balanced, that just really complicates things and seems a lot like "fully" balancing a cartridge, which already has a great ground with the groundig wire to chassis

Same thing here. When a cartridge is used as a balanced source none of the four pins is tied to ground. The ground is used purely to provide shielding, not as a voltage sink.

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The "balanced" they describe is different than what I think of as balanced. Instead, they are creating a push/pull effect on each headphone driver.

What do you think of as balanced? They are indeed creating a "push/pull" effect. That is exactly what balanced drive is.

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I wish they didn't use the term balanced to describe this.

Why not? In what way do you find it inappropriate?

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Struts, in the "balanced" headphone (not "fully balanced") are they not merely changing the point where the ground is common (moving it from the Y to the plug)? Looking at the diagrams linked to by Elk, that's the only difference I see. I see little point in that.

Dave,

As far as I can tell that diagram just shows a headphone with balanced cabling being driven by an unbalanced amplifier. Generally, unbalanced amplifiers don't sport XLR outputs so the real-world relevance of that diagram is a bit of a mystery to me!

What you are describing, if I understand you correctly, is a scenario where a balanced stereo cable (four conductors plus shield) is terminated with a stereo TRS plug (two conductors plus shield). In that case you would be correct, there would be no real difference between that and a two-conductors-plus-shield cable with a Y-joint in the headphone.

Elk,

I agree, the circuit diagrams in the Headroom article are slightly 'stylized' and therefore tend to become more confusing the closer one studies them!

However, to return to the original point, some headphones sound better when driven in this way. Although I think I understand the theory I don't pretend to be able to definitively link cause with effect, however I have heard the difference and I am definitely a 'believer'! Everyone else is of course entitled to their skepticism.