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
1) A TRUE "balanced" design can swing twice the voltage potential of an identical single ended circuit. The gain of such a circuit is not necessarily twice as high ( a lot of other factors here ), but offers greater power potential with the associated increase in headroom. There are designs that operate on a differential mode, but aren't "truly" balanced as most engineers / designers think of them.

2) "Internal noise generated in differential circuits tends to be less then that of the same circuits executed single-ended. In theory, about 6DB less, so in two stages of gain, this could be 12 db less! This is dramatic."

Notice that Ralph says "in theory". In reality, these figures are typically not achieved. There are improvements, but not to the extent mentioned. Quieter and cleaner IS quieter and cleaner though. Whether or not the benefits will be noticeable is obviously dependent on how good the original single ended circuit was to begin with. Hence my previous comments about "poorer" single ended circuits benefitting most of the additional noise cancellation of balancing. When you've got a relatively high noise floor ( compared to a quieter design ), lowering that noise floor is always beneficial. Whether or not going into the added expense of balancing such a circuit is a worthwhile investment compared to designing a better single ended circuit ( with a drastically reduced parts count ) is a matter of personal preference / budget for the designer / manufacturer. As a general rule, balanced designs typically require appr twice the parts count as that of single ended designs. Many will argue that "simpler is better", but obviously, that is a subjective opinion.

3) I agree with you here Ralph, but that is IF the rest of the system is up to snuff. Since most gear / systems are compromised in design integrity, the benefits of "true" balancing are many times not achieved in lesser systems with lower grade components. As you mentioned though, "Balanced amps built from the ground up sound better with balanced inputs for the simple reason that balanced sources sound better!". This takes into account "proper design" from beginning to end, not trying to impliment a superior design into a system based on lesser design integrity.

As a side note, our AC systems are "balanced" as transmitted and DC is single ended. While Eldartford has commented on low loss DC transmission over extended distances, there is a reason why AC was selected over DC. That is, with twice the voltage swing and multiple phases, loss is drastically reduced and the signal is kept cleaner over a longer distance. DC is both lossier and more susceptable to interference. On top of that, RFI is very easily superimposed on top of a DC voltage. That's why even after the AC mains have been rectified in the components power supply, you can still have RFI being passed into the circuit. As such, the installation of some type of "trap" or even "snubber caps" in a typical power supply can really clean things up.

4) I didn't really read much into Herman's response here but I should have. All sound is created by displacing air, causing both a pressure front and pressure drop i.e. a positive and negative. Strings move fore and aft or side to side, percussion instruments are compressed and then rebound, etc...

Other than that, i don't think that Herman has been a "great source of misinformation". I think that Herman has contributed many factors along the way that were both valuable and factual along with quite a few personal observations. Obviously, nobody is going to agree with someone else ALL the time. Rather than making a generic and cumulative statement such as "The bottom line is Herman is a leading source of misinformation", one should jump in and present rebuttal at the time that the statements are made or when first "stumbled across". This keeps everyone on the same path in the same time-frame without offering much time between the "misinformation" being presented and / or the possibility of it being futher distributed. In effect, "rebuttal" acts as a form of "damage control".

I'm not getting down on you Ralph as i surely appreciate your input. I wish folks like you came around more often. If you've read any of my previous posts making mention of you or your designs / gear, i think that you know that i have the utmost respect for you and what you offer us as audiophiles. Other than that, feel free to put your boot in my ass as needed : ) Sean
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Thanks for the input Sean, one always needs to know that there is sanity out there.

As you pointed out about the noise thing, I did use on purpose 'in theory'. In practice unless your circuit is way extra bad, 5db is easy. That means 10 db less noise in two stages is too. Often the noise rejection is more like 5.9-someodd- pretty close to 6 for most people.

Parts count in a fully differential circuit is not really all that bad, being slightly less then double the parts (although most are resistors which are not a big deal in the overall cost of an amp or preamp). Our preamps (and I make no bones about the fact that I walk what I talk) are fully differential and balanced and yet are less expensive then a lot of preamps that sound markedly inferior (if I do say so myself...).

3) I guess in the scheme of things, one would hope that what is strived for is the experience of recorded music sounding real. I would certainly hope then that the balanced source has its ducks in a row. If it is to be flawed for this discussion though, to be on the same ground the single-ended source must accept the same flaw(s). Given that the case, balanced sources would still tend to be better, if that flawed source is still considered to be balanced.

I've worked with this stuff for over 32 years now and I had often wondered why audiophiles did not take advantage of the benefits that balanced operation offerred. I am sorry for this, but if the best explanation is really no more then misinformation (or perhaps its own kind of damage control), -well, I don't buy it.

Having said that, I do believe there may be a different issue: some manufacturers got on the balanced bandwagon as they seemed to think is was a new trend. Most of those that I might put in that category do not seem to understand what the technology is about and have produced inferior products. Some of these are well-known. Held up to single-end products that are better thought out, I think such manufacturers have done the field of balanced operation in high-end audio a dis-service. My soapbox... -but since we were talking theory or that's how Herman made it sound, well, I reject on the basis of fact and experience just about everything he said in his opening post. What is disturbing is that it looks like people just ate it up. There's just too much of a mountain of evidence to the contrary; I just had to point it out.
Sean, good response, as was Ralphs. You have acknowledged many of the positive aspects of balanced circuitry noting the absolute most important point. Most notably, your point #3.

There are MAJOR differences between "quasi" balanced circuits and "true" balanced circuits. This factor MUST be recognized when evaluating. Installing XLR connectors on a component does not a balanced circuit make.

I provided the Jensen link (Bill Whitlock), in hopes that persons would familiarize themselves (if not already familiar) with the actual differences defining "balanced" vs. "true balanced" circuits. It clarifies with a high degree of accuracy and very little sales "slant".

Herman had mentioned the additional expense of manufacturing components with provisions for balanced interconnection and throughput. Well? This is partially accurate. Many quality manufacturers incorporate "true balanced" configuration as "standard equipment". I didn't "option" any of my components with "true balanced" configuration. It was already there. Maybe that could be considered an added benefit of a $5000 integrated? Along with chassis dampening, airborne and structure borne vibration control, high quality close tolerance components, short signal paths, etc, etc, etc. In short? Sound engineering practices.

Bottom line? If balanced configuration is utilized "true to form"? It has many benefits over single ended. Once again the key words being "true to form".

"True to form" is NOT a Ferrari with a Chevy motor in it.

Dang! Spot on!

I can't tell you how often I have people call me thinking they have a 'balanced' input on what is clearly a single-ended amp! Just 'cause you have that connector- don't let that fool ya.

I would think that it goes without saying that a 'balanced' amplifier or preamp was built that way from that ground up, but it isn't always that way.

Also, we probably ought to discern the difference between balanced differential and plain old balanced. Balanced differential is usually the simpler of the two, and generally quieter. Some of the ARC amps from the late 70s were balanced but they were not differential and they were also extremely complex. Complexity is definately not a prerequisite of balanced operation as differential circuits can be quite simple.
My McIntosh 2102 has balanced inputs but then it converts the signal to unbalanced which means there is just more adjustment before amplification.

Thus, using the unbalanced inputs in this case is better which is the opposite of my Audio Aero Capitole Makr II CD player's connections to my matching Audio Aero Capitole Amp which makes for perfect bi-amping in my home: unbalanced to the McIntosh and balanced to the Audio Aero....all from the same Cd player.