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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
marakanetz's avatar
marakanetz
5,473 posts
 

Sean,
circuit balancing not neccessarily can be achieved through so not favorable larger negative feedback, but electronically by the diode blocks between a complementary pairs of amplification (that's how it's usually done on SS amps) involving no extra negative feedback. The same could be applied to tube amps and it won't be a "violation of a tube purity". In terms of distortions, noise, bandwidth it's always dealing with gains and losses in any of the above said cases.
sean
6,231 posts
 
Marakanetz: Diodes in themselves are "dirty" creatures and they too would require matching. Every diode has a different turn-on and recovery rate. Once again, you end up with more parts and more matching. Sean
>
jafox
1,456 posts
 
Herman,

Thank you for a detailed report on this subject. However, I am not convinced of a few issues made here.

Issue 1: I wired a phono cable in both SE and Balanced configuration to feed an Aesthetix Io phono stage. This was a SilverAudio SilverBreeze cable. There was indeed a gain difference which I compensated for to get the same level. In some cases, at this stage in a system, this extra gain can be very valuable. But there was also more low-level detail with the balanced cable. I do not know if this was due to the nature of the cable in this configuration or the Io's inherent design but in my case, it was very clear of the sonic improvements. I have been eager to try this with the Manley DAC into my line stage but I do not have RCA and XLR cables of the same brand/model to do a fair test.

Issue 2: The situation where noise rejection from within the interconnects is achieved, I find this valuable in itself. My system is in a very noisy environment, sump pumps, cable company transformers, furnace, etc., and any kind of rejection simply has to be of value. My pre-to-power length is 20' and so perhaps is not a big issue, but again, until I can compare an RCA vs. XLR cable of the same brand/model, the jury is still out for me on the benefits or not here. Perhaps the issue of "filtration" is something I need to attend to, but why do I need to go through so much effort to condition my power? Should not components be designed to resolve this for me?

Issue 3: I am unsure of your conclusion here. You point out that in theory the two phases of a balanced circuit can not be equal. So if a product has been designed to its best ability to have two "matched" phases, I would think that grounding out one of these and running single-ended should be an improvement. Afterall, one of the compromised phases is out of the loop and the power supply should ultimately have more headroom as well. It most likely is not as good as another product of the same price that was a single-ended design, but the balanced product with one phase grounded should be better than with both phases if there is indeed no benefit to the 2-phase implementation. And yet, I suspect the engineers at ARC, BAT, Aesthetix would not think so of their products or they would have dismissed the balanced implementation and focused their attention to putting all their money into single-phase designs. Of course this is what CJ, Lamm, CAT and others have done. What we all would need here is to hear the comparisons of these company's designs throughout their R&D efforts when they made these balanced vs single-ended decisions at those times.

Issue 4:
You award balanced designs 3-strikes because the conversion from single-ended is not perfect. I think we all can agree that the world of audio electronics and music reproduction is not even close to perfect. But we are also in an analog world. So do we assign 3 strikes to digital recordings because the analog to digital conversion is not perfect? As a long time phono fan, I have come to like the sound of much digitally recorded music.

I understand that many products have XLR connectors, step-up transformers, etc., to give the user a false claim of balanced benefits. But I simply have to believe that there are benefits of truly balanced designs for home audio or a number of talented audio engineers would have abandoned this by now. And in the few limited comparison tests I have made, there is indeed benefit.

John
driver's avatar
driver
750 posts
 
To my ears having had a completely balanced home audio system sounded wonderful with XLR cables. For grins I switched to RCA cables & although still nice, it didn't have the fullness as before. This particular gear sounded better balanced & that's how I ran it.

I also do pro audio sound & of course all our gear is balanced for the simple reason of noise reduction. Also there's the bennie that the connections are more solid & although one is not likely to go running past the back of their rack, there's comfort in knowing the connection is secure.

I also wouldn't use pro audio gear in a home stereo because it's not the best amp for the job, although it will work. Don't take this the wrong way but if someone wants to buy a balanced piece of home audio equipment, there's not much you can say that will dissuade them.

As an aside, I've used both types with very good results over the years & using XLR connections has proven to me that apart from the topology, XLR is the way to go. Why does somebody prefer SS to tubes or analog over digital? It's a matter of preference because even though you've heard it a thousand times, it bears repeating-if everybody did the same thing, audio (as well as anything else) would be very boring.

Sean, it was me that you were emailing a few days ago about why I was selling my Ayre & I did enjoy our "talk".
eldartford
4,262 posts
 
Sean...I know how you feel about Op amps. I halfway agree with you on this subject, but only because Op amps are so often used in unsuitable applications. However, a unity gain buffer (which you need two of for a balanced line output) is an application wheren the Op amp is entirely satisfactory, and use of discrete circuitry would be a waste of money, and probably yield inferior performance.

I have done a lot of amplifier "bridging" before that term was coined, in particular as a way to drive a center speaker from a stereo amp by inverting one channel's signal. It seems to me that an amp in bridged mode would exhibit many of the advantages cited for balanced lines, yet it is commonly reported that amps in bridged mode don't sound so hot.

Finally (?) why do the two sides of a balanced line need to be matched? The whole idea is that the signal is floating, and can be received with a differential input amp that rejects common mode noise. If you ground one side of a balanced line (the extereme case), I think that you just revert to single ended.
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