balanced is inherently flawed


A recent post asking for opinions on balanced vs. single ended got me thinking once again about the inherent flaws in a balanced scheme.

A balanced signal has 2 parts called plus (+) and minus (-) that are equal in voltage but opposite in polarity. Therefore a balanced amp is really 2 single ended amps in one package, one for the + singal and the other for the - signal. So a balanced amp using the same quality parts as a single ended amp will be twice as expensive. Strike one.

That brings us to the "equal but opposite" notion. In order for this to work as planned, all of the + stages and cables connecting them must be exactly equal to all of the - stages all the way through the source, preamp, and power amp. Any deviation from the + stage being the exact mirror image of the - stage will result in an imbalance. Since perfect symmetry cannot be achieved, especially with tubes, distortions are introduced. Strike two.

Some think that balanced has to be better for various reasons that include:

1. If they hook up a balanced device using single ended cables they loose some gain.
2. They think a balanced system can achieve a lower noise floor.
3. They have balanced equipment and it sounds better when they hook it up with balanced cables vs. single ended cables.
4. It's used in recording studios by the pros so it must be better.

These arguments are flawed for the following reasons:

1. More gain does not equal better sound. Of course you need enough gain to drive your speakers to satisfactory levels, but the fact that one connection has higher gain than another has really nothing to do with sound quality.

2. This is the most misunderstood of all. A balanced amp CAN reject noise that is coming in through the interconnects. However, it can do nothing to reject or cancel the random electrical noise that comes from within the devices inside the amp. A balanced amp has no advantage over a single ended one when it comes to the major contributor of noise in the system, that which is generated inside the amp. The rejection of noise from cables relies on the fact that it is generally equal to both the + and - inputs and is therefore cancelled, but since the noise voltages generated by the devices inside the + and - stages in the amp are random and unrelated, they do not cancel and are passed on to the next stage.

Furthermore, since well designed, shielded interconnects of any type are very good at rejecting electrical noise from the outside, balanced has no advantage except in very noisy enviroments or when using very long runs, both of which apply to recording studios, not to typical home systems.

3. Since a truly balanced amp was built from the ground up to operate in a balanced mode, it makes sense that it will sound worse when fed a single ended signal. That doesn't mean that balanced is better, just that that particular amp sounds better when fed a balanced signal.

If you subscribe to the theory that more money can get you better performance, and since a single ended amp has 1/2 as many components as an equivalent balanced amp, it stands to reason that if the designer put as much money and effort into designing a single ended amp, it would sound better.

4. See 2 above.

And this brings us to our last point. ALL sound sources are single ended. Whether from a plucked string, blowing air through a horn, the human voice, or anything else; the resulting increses and decreases in air pressure that we perceive as sound are single ended. There is no "equal but opposite" waves of pressure. This is also true when the signal finally gets to a loudspeaker. There are no "equal but opposite" pressure waves coming from the speaker. It is a single ended device.

In a balanced system these pressure variations are picked up by a microphone and then some where along the line converted to balanced. A phonograph record is encoded single ended as is a digital disc. Your CD player may have a balanced output but the data that is read from the disc is single ended and then converted. In order not to introduce ditortions, this conversion from single ended to balanced has to be done perfectly. And since it can't be, strike three.
herman
Sean...IMHO, We are talking about such low voltage/current level signals that connector contact resistance is of little consequence. The practical advantage of DIN connectors is that they lock in place. RCAs are easily pulled out.

Any time you use a stereo amp in bridged mode your speaker wires are "balanced mode". I have always found bridged mode to be good, (assuming that the amp can handle the load impedance) and I don't understand why some folk don't like it.
Hi Sean, I'm not a big fan of the DIN plugs either. I was just commenting that they seem to be a sort of British/Euro tradition. Get careless, trip on the cable or step on a connector on the floor and its toast. I had to make up the cable for the Echolette I mentioned- what a pain.

Some people that are neater then me won't have these issues, but come to think of it, 1/4 phone plugs are about the only thing you could step on without hurting it right away.

Further thoughts on the speaker issue... almost any dynamic driver would be considered balanced, but few crossovers are. There are dual VC dynamic drivers out there FWIW. Some planar speakers are balanced too. Seems to me some of the Maggies (later ones), ETs and certain ESLs. In the case of a loudspeaker, the balance issues have much to do with the Electromotive device the speaker employs, sort of the reverse of a balanced pickup (like a phono cartridge). IOW a speaker that is not balanced is really the exception rather then the rule
Herman- Glad that you have been listening to your system. I was going to make you an offer (shhh! the wife is looking over my shoulder).

Russ
I just stumbled upon this thread today. Well, obviously, Bill Johnson at Audio Research, Nelson Pass, Jeff Rowland and many other designers (in addition to Ralph) of some of the best amplifiers have a lot to learn. I'm really glad to see Sean and Herman set them straight.

(Gentlemen: Please tell us about your educational backgrounds and whatever other qualifications you might have so Audiogoners can take that into account. I think a lot of people would like to know.)

I'm not saying you're wrong. I'm just curious. It could be that you've published in peer-reviewed journals and all of your claims are absolutely valid. If so, please include references. Thanks.
Do I detect a note of sarcasm?

First, I have credentials but that has nothing to do with it. All the education, qualifications, references, and published papers in the world won't change the fact that either I'm right or I'm wrong. Even an uneducated fool is right sometimes.

Secondly, a list of designers that embrace a balanced design doesn't mean anything. I can rattle off a list of well respected single ended designers that proves just as little.

Whichever side of this you land on you must admit it was an enternaining thread.