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jalo said:

Don't bother

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Sounds good, thanks.
 
 

koonhua90 said:

I fixed it for you. Measured by the ears, analysed by the brain.

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Yep, and the brain's the problem.

No matter how you see it, from an engineering point of view the measuring instrument is the ear. Not everyone can hear the differences between each harmonics, more so 0.1 Hz. Even if your brain detects it, whether your conscious mind knows it is another issue.
 
Going balanced while using the same circuit topology will improve your S/R ratio, and that alone is an improvement in terms of SQ that can be measured. Not only that, you will have better PSRR ratio against noise in the power supply, and also DC noise in input will not have effect on your output signal. As for all the other things that cannot be measured easily, use your own ears to hear it. Just my 2 cents.

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koonhua90 said:

No matter how you see it, from an engineering point of view the measuring instrument is the ear. Not everyone can hear the differences between each harmonics, more so 0.1 Hz. Even if your brain detects it, whether your conscious mind knows it is another issue.
 
Going balanced while using the same circuit topology will improve your S/R ratio, and that alone is an improvement in terms of SQ that can be measured. Not only that, you will have better PSRR ratio against noise in the power supply, and also DC noise in input will not have effect on your output signal. As for all the other things that cannot be measured easily, use your own ears to hear it. Just my 2 cents.

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An improvement to SNR is only an audible improvement if the SNR is low to begin with. A better PSRR will only be audible if there's audible power supply noise to begin with. Same with DC noise. So ultimately it depends on the amp. As a result, I still don't see a reason to go balanced over a well-engineered single-ended amp. Balanced amps seem to solve problems that aren't real problems.

 
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head injury said:

An improvement to SNR is only an audible improvement if the SNR is low to begin with. A better PSRR will only be audible if there's audible power supply noise to begin with. Same with DC noise. So ultimately it depends on the amp. As a result, I still don't see a reason to go balanced over a well-engineered single-ended amp. Balanced amps seem to solve problems that aren't real problems.

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Not going balanced amp will certainly save you quite some money 
 
The issue with amp is that some people like it to be like 'wire with gain', while some people prefer it to be 'tube-sounding'. In my opinion, one apparent advantage of balanced amp is the bigger swing of voltage and bigger output power that can be provided, with its downside being the much higher power consumption compared to single ended. For high end headphones I will definitely consider using balanced amp, but for earphones I would prefer to use a slim and tiny amp.
 

Voltage swing isn't really an issue either. The hardest regular headphone to drive is the Hifiman HE-6. It has low impedance and very low sensitivity, a deadly combination. It needs about 5Vrms to get to 110dB. A $112 Fiio E9 can do that into 50 ohms, and that's with its 10 ohm output impedance. The next hardest headphone to drive that I know of is the Hifiman HE-4 and HE-5. They need about 5Vrms to get to 115dB. The E9 can handle that into 38 ohms, too.
 
Granted the E9 doesn't have the best noise level or distortion performance at low impedances. You don't need a balanced design to solve those problems, though. The Objective2 amplifier gets most of the way there if not all of the way there on AC power, and is transparent with regards to distortion and noise.

^ In your opinion, what do you think are the real problems?

With what? Single-ended? I don't know of any.

The whole issue with portable amplification. You mentioned that you see no point of going balanced, does that apply to both portable and home set up too?

For the most part. Lower crosstalk would be more helpful with a portable amp than a desktop amp considering portables have to be small. Lower noise might be handy with sensitive IEMs. Power is basically a non-issue for portable use, unless you plan to use inefficient headphones on the go. If so, there are specialty single-ended portable amps that will do the job fine. The Rx MK2 seems to fit that bill. So that's one benefit of balanced amps made unnecessary for portables, and two that might help. However, the disadvantages are also worse when portable. Power usage could be an issue when running on batteries. Correct me if I'm wrong, but a balanced amp would probably be larger as well, and less portable.
 
I'm biased in this case, though. I don't see any point in portable amps, period. IEMs are the only things I would want to use when on the go, and they're almost all very efficient.

if this hasn't been mentioned already there is one very simple fact to note about the OP's experience.
the sr71b simply sounds better via its balanced output  mode..
 
Whether or not this improvement is actually due to the rig being partially or fully balanced is irrelevant, the simple fact is that this particular amp, in this particular balanced output mode sounds superior to its single ended option. 
 
I would say its easily noticeable even to someone who is not a golden eared fanatic. i can tell you this from experience and if you do some searches you will find my sentiments echoed.
Skylab, for example also confirmed this to be true.

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br777 said:

if this hasn't been mentioned already there is one very simple fact to note about the OP's experience.
the sr71b simply sounds better via balanced output  mode.. and i would say its easily noticeable even to someone who is not a golden eared fanatic. i can tell you this from experience and if you do some searches you will find my sentiments echoed.
Skylab, for example also confirmed this to be true.
 
whether or not this is actually due to the rig being partially or fully balanced in the case of a db2 or the like, is irrelevant, the fact is that this particular amp, in this particular mode is simply superior to its single ended option. 

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This brings up a good point I was considering. Balanced design has its use in the sense that it can correct a poor single-ended design. The three symptoms it seems to cure are noise, crosstalk, and power. Take a mediocre single-ended amp with weak output and poor measurements, put another next to it, and you correct some of the issues. Maybe that's what's going on with the SR71b. It might be easier to swallow than one alternative, which is the single-ended mode is purposely handicapped to make balanced look better. That's too "conspiracy theorist", even for me.
 
At a glance balanced doesn't seem necessary if the single-ended version is well-designed though. It has advantages but they only seem useful if the single-ended amp can't keep up on its own. Case in point, the Objective2. Biased example because I love the design and want one badly, but I don't see any benefit to throwing balanced circuitry into its design.

jalo said:

A bridged amplifier is not the same as a balance amplifier.  The balance concept is not that hard to understand either (see below references).  These days, you don't really need to use balance phonostages to get balance sources.  Digital sources can do the job just as good.  To me, the elimination of common ground, a fully differential discrete and independent channel, noise cancellation, channel separation, not only left versus right, but four discrete channels combine to made a big difference to me.  The problem with a bridged amplifier is not only the power is increased all the other problems also get increased.  When the power of a balance amplifier is increased, it keeps the other problem out.  I don't think Sperandeo hears only a louder volume, he hears improved sound quality.  But to each his own.
 
http://www.headphone.com/learning-center/art-i-balanced-vs-unbalanced.php
http://www.headphone.com/learning-center/fully-differential-balanced-drive-sources.php
http://www.headphone.com/learning-center/art-ii-balanced-transmission-vs-fully-balanced.php
http://www.headphone.com/learning-center/art-iii-balanced-sources.php

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What are you talking about?

You casually dismiss phonostages in favor of digital.

Sorry, but that doesn't work. I run a turntable because something like 60% of music recorded before the CD was introduced never made it to digital.

I spin LPs so I can access music that is not available on CD. So, no, a balanced CD player or DAC isn't going to let me play music that isn't available on digital.

Further, my 1960 all-tube stereo FM receiver isn't balanced. Neither is my Icom IC-756Pro II wideband transceiver. As far as I know, there is no balanced wideband radio receiver. If you don't know, there's more to the radio spectrum than AM and FM. I listen to those other bands.

Balanced operation is mostly hype and placebo. It "solves" a lot of non-existent problems at a high price and most who think they're "balanced" are actually running single-ended. Cognitive dissonance kicks in something awful at that point, so we get a lot of excuses as to why single-ended is equivalent to balanced and better than single-ended even though it is technically single-ended.

Yet another venture into the land of audio make-believe. It's a lot cheaper and just as fun to pretend that a cardboard box is an airplane. Children "get" this, but the point is lost on audiophiles.