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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
atmasphere's avatar
atmasphere
11,640 posts
 
OK- good questions. Here we go:

I use tubes because the distortion they generate is less annoying to the human ear then the distortion of transistors. This has to do with odd-ordered generation that transistors do. Even in vanishingly small amounts, the ear is sensitive to this. Tubes don't make nearly as much of this distortion.

To get rid of the noise of tubes, I use balanced differential circuits, and acheive noise figures 5-5.5db less per stage of gain then I would have if operated SE with the same topology. In a preamp with 3 stages of gain, this is close to 18 db less noise as compared to the same topology in a single-ended embodiment. Don't tell me you can't hear that! Reducing the noise floor means more detail, and detail is a highly desirable characteristic of a good system.

You hear differences in cables due to several factors:
1) termination impedance
2) characteristic impedance of the cable.

The two are related. Since most SE cables are terminated with 100K or more in most cases, the capacitance of the cable can easily interact with the input impedance of the amplifier to result in a high frequency rolloff that is quite measureable and audible. This introduces measureable and audible phase shift. Since different cables have different capacitances, the roll-off and phase shift is different from cable to cable. You also have termination losses due to the connectors themselves, and reflections due to the characteristic impedance of the cable being poorly terminated by the input of the amp.

With balanced lines, the cable issues are swamped by the impedance of the driver circuit and also by the input impedance of the amp, which if done properly, are both quite low. With low impedances, the capacitances and other cable issues are pushed out to frequencies well outside the audio band (and the propogation delay in the cable is improved too- up to 8X better). This is easily heard and measured.

You may get 100KHz out of SE designs, although most tube based SE power amps will not do anywhere near that, but the real issue is can you get that signal *into* the amp from a distance. You might be able to over a meter or two, but not if the cable is ten meters long. Over that length, the high frequency roll-offs will be too severe. You need balanced lines to do better.

If you wonder why I brought up Mercury, the point was that a *microphone* signal went over 150 feet to get to the tape recorders. Just go ahead and see of you can get a hifi signal out of a single-ended cable that is 150 feet long! You can't. Now I know that no-one uses cables that long at home, but what happens if you are interested in that last degree of nuance that is possible? Well I can tell you quite simply that the better your cable is, even if its only 3 feet, the more nuance you will transmit. And audiophiles are all over that nuance stuff. That's what makes good things happen in good systems. If you want that last degree of nuance, you have to use a balanced sytem to get it, particularly if you have any real length in the cables.
sean
6,231 posts
 
Two things Ralph.

"Not that I'm saying that SE is bad, just that balanced (done right, which is not that hard) is better and *any* audiophile can hear it. I had a girlfriend who was deaf in one ear, and half deaf in the other, and *she* could hear it, so I am confident you can too if it give it a straight shot."

Someone that is highly respected, both within the Audiogon forums and audio industry on the whole, publicly commented that they did not like your preamps at ALL. On top of that, the preamp that they ended up running is being utilized in single ended mode. Given that they've run your amps and found them to be a quality product, how would you respond to that?

As a side note, a reduction in noise of -18 dB's is equivalent to having 1/64th the noise floor that you started out with. As Herman points out though, if the noise floor is already well below audibility, how much of a benefit is it?

There's another thing that you're overlooking Ralph. That is, ALL amplifier / speaker interphases are "single ended". Why this is, i don't know.

If you think about it, a "balanced" dynamic driver would be simple to make AND offer drastically improved transient response. By using two coils in parallel ( one positive and one negative ) and driving them with a common center tap ( ground ), you would literally have ( near ) instant acceleration and deceleration potential. When one motor was pulling, the other would be pushing, etc... They would end up sharing the load AND cancelling out / drastically reducing the effects of reflected EMF. Why hasn't anyone done something like this? While it would take an all new speaker AND amplifier design, i see no reason why it couldn't be done successfully.

Once again, the "high end" and "high tech" audio engineers / manufacturers "sleeping on the job". Sean
>

PS... I'm a "more is better" kind of guy, so i'll take any reduction in noise / increase in power that i can get. Having said that, only one of my systems is running in balanced mode.

PPS... An E-stat would lend itself to "balanced drive" also with no need for a transformer. One could use high voltage output devices in the amplifier and directly charge the two plates and mylar. By varying the positive and negative potential between the plates, the mylar, which would be grounded, would be repelled and / or attracted uniformly across the entire sheet in both directions. Only problem here is that you would have one helluva safety hazard to deal with when energized / playing music.
buscis2's avatar
buscis2
468 posts
 
Atmasphere, I find it hard to believe that you are still beating your head against the wall on thi issue. I have to credit you for your tanacity. I responded to this thread several times with what I considered useful information, fully encompassing all aspects of balanced designs, obviously to no avail. If one was to read, evaluate, and retain the information previously provided, there would be no requirement for this redundancy.

If the personal factors were removed from this thread, it would have ended 27 responses ago.

For those of you who agree or disagree, at the very least, take the time to acknowledge the provided information in this thread and be willing to understand the technology. Stop thinking that all information by manufacturers is only being provided to sell you something. A lot of that is also a matter of interpretation.

Your mind is like a parachute. It only works when it's open.
herman OP
2,216 posts
 
Ralph, if I may be so bold as to call you Ralph, thanks for all of the information you have provided. I think we've run our course here, but I've learned a few things and been reminded of things I learned long ago but forgot. I may be a bit pig headed but I'm not stupid. You haven't convinced me that the advantages outweigh the disadvantages, but at least you've piqued my interest in your products and I would love to hear them. That can't be all bad.

And here is something we can agree on that relates to what Russ says above. One huge weakness in the standard SE scheme is the use of RCA connectors. In a nutshell, they suck, but Russ, the fact that a DIN connector has enough pins that it could be used to carry a balanced signal does not make it a balanced connector. The fact that Naim chose to address this weakness by going with a more robust DIN connector does not mean that they "provides much the same result" as being balanced. The earthing scheme may be improved, but other than that it provides absolutely none of the benefits that Ralph has been pointing out with regards to being balanced. Oh, and yeah, I listened several hours yesterday and enjoyed myself immensely. Thanks for asking :>)
atmasphere's avatar
atmasphere
11,640 posts
 
Hi Sean,

The interface to a speaker really depends on the amp, not the speaker. The reason is that the speaker floats, and if you change the connections to it, all that changes is the phase. OTOH, some amps drive a speaker SE and others are balanced. Ours drive it balanced of course, either speaker terminal is floating (not connected to) ground. Some speakers have balanced topologies in the crossovers and other don't.

With regards to the question about the preamp, I'm not able to answer the question as I don't know any of the particulars. I can tell you this: On older MP-1s we used a vacuum tube regulator and there were two problems with this.
Some people did not put in the tube (did not or would not read the manual), and while the preamp would work this way it certainly would not sound right. The other problem is that the tube would fail and the preamp would continue to run, again in a compromised state. Newer MP-1s have this issue fixed with a semiconductor regulator that is impedance, temperature and short protected (and is an order of magnitude better regulation and smoother impedance). That would be my guess about what was going on.

Herman, I agree that RCA connectors have plenty of weaknesses. RCA developed them for purposes other then audio and we have been making do ever since. I prefer a connection that locks in place somehow (like 1/4" phone plugs; I also appreciate their robustness), but that's just me.

My soapbox: If high end audio as an industry went to 1/4 phone connectors, we could use balanced and single-ended connections intermixed, as 1/4 phone plugs can support either. A lot less screwing around...

Naim, being British, is typical of using DIN connectors, like other Euro manufacturers. Its kind of a tradition- I have an old Echolette (used by musicians) made in Germany in the early 60s) that uses DIN connections. DIN connections can be used about any way you want- balanced, SE either in mono or stereo, or as SE inputs/outputs. BTW, Naim uses balanced circuits as elements in their power amp circuits. Just thought you should know :)

Buscis2, thanks for the comments. I've taught more then one class in the past and the education aspect definately gets away from me. High End Audio being what it is, you can spend *WAY* too much money and wind up having a stereo that essentially sucks. I see no point in that, so if I can be helpful I do give it a try. On these forums, I try to stick to what I know and stay away from those things for which I have no passion.
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