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. |
Hi all, sorry it took a while to get back to this.
Herman thought I did not present some balanced sources, so I will repeat myself. Nearly all phono cartridges made today are balanced sources: the Shure M-95 from 30 years ago was a balanced source, as is a Titan or a Ruby made today. Ever wonder why mag phono is the only source that requires a grounding wire? Most balanced sources that you try to run single-ended behave this way unless you ground loop the signal with the ground. Or have a grounding wire...
Microphones such as the Neumann U-67 are balanced. So are RCA DX77 ribbon mics. If you wonder why I bring up recording equipment, its because we all listen to this stuff in our recordings: Nearly all LPs and CDs are mastered using balanced connections and equipment.
When you think about it, there really aren't any true single-ended sources. I suppose a tuner might be, but the radio station makes the signal in the balanced domain, so really the tuner is a signal filter of sorts... A CD player might be, but the laser beam is picked up by an optical device, which has an output that is balanced (although its not always used that way). Certain lo-fi devices are single-ended- cheap ceramic microphones for example. No-one in high end audio uses them though :)
I was also chastised about mentioning the phone company. Its not as obtuse as you might think, but you do have to know some history. I'll try to explain it better. Before balanced lines existed, there was no such thing as long distance more then a couple hundred miles as definition was lost very qucikly. You had to yell at the top of your voice to be heard. Balanced lines were developed as a solution, and due to the increase in definition and improved signal transmission, continental and intercontinental phone calls became possible.
The recording industry quickly realized the benefit: lower noise, much lower loss of signal detail, lower distortion and dramatically increased immunity to interconnect cables (does this sound like anythihg audiophiles might be interested in too?). By the early 50's, balanced lines were in place throughout the recording industry and ushered in the age of HiFi and the Golden Age of Stereo.
There was an important point there. These are things that audiophiles find important! Increased definition? Lower noise? Lower distortion? Immunity to cable weaknesses? Yes. We find these things to be important as they bring us closer to the musical experience.
For some reason (mostly cost), balanced line remained the domain of the professional market until the 1980s, when the first balanced gear for the home appeared (FWIW the first balanced tube preamp was made by us in 1989). It took 30 years, but finally balanced line was available for the home with the same benefits to audiophiles that brought them HiFi in the first place.
These days it is hardly more expensive to build balanced stuff as it is to build single-ended. Look at the tube preamps that are out in the marketplace and you see what I mean. Most of them are single-ended. The few that are balanced do not cost any more then the competition. With semiconductors, OpAmps all have balanced inputs. If you are running semiconductors its almost harder to make single-ended. For the record.
The gain thing:
Balanced allows for the same gain with less noise, close to 6 DB less noise, easily achieved. Despite imperfections caused by mismatches, tube issues and the like this remains true. When people say otherwise its because they have not played with these circuits- if they had then they would know!
Another interesting fact about balanced differential circuits is that there is a distortion-cancelling feature. This effect works even if the circuit is not perfectly balanced. Again, if you work with this stuff, you find these things out.
It is possible to operate things like EQ for LPs in the differential domain, and never have to worry about how well balanced your circuit is: the EQ will always be correct.
Volume controls and switches when executed in the balanced domain tend to be more accurate and less noisy then when the same types of switches and volume controls are single-ended. To give you an example, let's say there is a defect causing a volume control to drop out at a certain level. With single-ended, the signal is gone! With balanced, the signal drops only 6 db. In the case where a stereo volume control had poor tracking from channel to channel, with the balanced version the tracking problem would probably not even manifest until things got a lot worse (to the point where the SE version would be unusable rather then inconvenient).
I can offer a ton more of things like this, so again I have to state: Herman is wrong on every point offered. So Herman, contact me off line (or call me) and I'd be happy to fill you in. There are also a number of fabulous texts on the subject if you are interested. This is not about anyone taking a drubbing, I'm happy to help out.
And finally, I appreciate being allowed to try to set the record straight. Again, if you don't believe me, there is a mountain of evidence out there that shows how balanced lines perform better and there is no evidence to the contrary (although there is a lot of hearsay). There is a lot of myth, and in general audiophiles (myself included) tend to let go of these myths slowly if at all. We have to be constantly vigilent about this sort of myth if we are to advance the state of the art. |
Hi folks,
Hate to bring this up but all of Herman's arguments are completely flawed! As you might expect me to say, but all I have to say is, if you've not tried it, you have no idea what you're missing.
I'll give you some examples (refer to the leading post above):
1.>
This is inherently wrong, as balanced does not have inherently more gain. It has the same gain, just with less noise.
2. This is the most misunderstood of all...
It appears that this in one of the things that Herman misunderstands the most. 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. Additionally, differential balanced circuits can also reject noise in power supplies. This is called Cross Mode rejection, and is a spec, in addition to Common Mode rejection, that all active balanced circuits have.
3> sheesh...
Balanced amps built from the ground up sound better with balanced inputs for the simple reason that balanced sources sound better! This is because of various things, but a good example is that balanced cables can deliver the signal better. If you don't believe me, look at the phone company. Before balanced lines existed, transcontinental phone service was impossible. That is because of all the losses that are are associated with single-ended systems. When balanced line came in, so did long distance. The same benefits work well in the home too, as balanced connections send the signal from one component to another with far less interference from the cables!
4> double sheesh and Geez...
Finally, here are some balanced sound sources: All phonograph cartridges (with the exception of certain ceramic cartridges and the old Decca cartridge). All tape heads. All decent microphones. All LPs are cut with balanced equipment. Most CDs are mastered this way too. In fact, 99% of everthing you listen to had balanced circuitry as part of the signal's makeup. Mercury Records could never have made all those recordings without balanced lines as in some cases they had to run the mic cables over 150 feet. Same for RCA, Decca, EMI, in fact nearly every record label in the world.
The bottom line is Herman is a leading source of misinformation. Sorry to say it, and if y'all want to look at my previous posts you'll see I try to not flame people, but this sort of blather can't go unchallenged. Forums like this should be about the truth for God's sake and ours. |
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. |
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. |
Hi Herman,
Its obvious to me that you're not getting what I am talking about else you would not be responding this way. I'll try it another way, maybe you'll see.
One of the things balanced does for you is it helps get rid of cable problems. That is how come Mercury was able to park their recording truck behind Northrup Hall in Minneapolis in 1958 and then ran their mic cables over 150 feet from the hall to the truck, and got a recording that is still considered state of the art today. If there were the cable problems that audiophiles see routinely today, this would simply not have been possible. Mercury did this in 1958 when no exotic cable industry existed at all. How did they do this? Balanced Line connections.
You can't say that this has no effect on you as an audiophile- Mercury's recordings are legendary. Now, if you could have a cable system in the home that eliminated cable problems, so you could run 30 or 50 feet of cable without any high frequency loss, without any loss of low level detail, for that matter sounded excellent regardless of the cable you used, would you be interested? If you say no, you will not be in agreement with most of the audio community. These are very real benefits of balanced lines, and they have very real benefits for audiophiles who use them in the home.
I used the other industry examples to make a point, which was that these industries benefited from this technology for the same reasons that audiophiles can:
Lower noise
Lower distortion
cable immunity
wider bandwidth
These are very real benefits and are readily audible.
Yes, a light sensor (from a CD pickup) is a balanced device. It has two leads, neither of which has to be tied to ground to work properly. That's how most balanced sources work. How a designer chooses to use the device is a different story, just like a phono cartridge, which is another inherently balanced source. Sure, you can use it SE, most people do, but at the end of the day the cartridge will not care how it terminals are connected, as neither side of the inductor is tied to ground. That's how balanced sources work. If you let both sides of the cartridge float, and just use the tonearm as a shield, along with the shield of the tonearm interconnect, you have a very elegent and simple balanced setup. Nothing to it. Its actually *harder* to run the cartridge SE, as noise, hum and RF interference are harder to get rid of and you have three connections to make instead of two.
I'll revisit the noise thing for a moment. Its possile to build a phono section with less stages of gain then ba single ended phono section, using a differential topology, one that can work directly with low output moving coil and yet be quiet. Now, if you can eliminate a whole stage of gain, you have less distortion, wider bandwidth and greater definition all at once. Audiophiles like that sort of thing. Sounds better. That's a very real benefit, its already in service in the field, and it connot be denied.
It would be nice if this was a case where we could agree to disagree, where this was all opinion. But this is not about opinion, which is why I feel compelled to set the record straight. There's a lot that I don't know, like, for example, anything much about saxopones. Kenny G kinda wrecked that for me. But I have been working with balanced circuitry for the better part of 30 years, and seen repeatedly how much better it performs then single-ended approaches to audio. 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. You know, just the facts. |
Hi Herman
I see that you do not understand how balanced signals works. That's OK. Here's a short primer:
Any signal source (transducer: either electromechanical, inductive or light) that does not use ground as a reference is a balanced source. What this means is that as long as one of the output leads of the device will work as well as the other, and switching them only means that phase has been reversed, then the device is a balanced source.
Phono cartridges are like this, tape heads are like this, microphones are like this, light sensing pickups are like this. So *IF* you wanted to, you could use the output of a laser pickup in the balanced domain. There are CD drives that do this out in the field and in service; I read about a company doing this over ten years ago! I don't keep up on digital technology as much as analog so I don't know of current (no pun intended) examples. Now the fact that this is the case is probably not really very important, since the analog signal that comes off the light pickup is interpreted as a digital signal fairly close to the pickup itself.
Herman, to say that what happened with Mercury in 1958 has nothing to do with how your system operates is flat wrong. Here's how I know: What does you stereo sound like with nothing playing on it? Hopefully, silence, or very near that. Where does the recording come from that you play? A: The record labels, unless *ALL* the recordings you play are made by you or your friends. IF not, then the effects of balanced line technology are all around you, in every commercial recording you play. Its inescapable. Therefore it is impossible that this has no effect on your stereo, unless you just plain and simple do not play recordings on it.
That we are not talking about opinion is very simple as the benefits of balanced line are one of the few areas of audio that are both audible and quantifiable. There are plenty of ways to 'determine what sounds better', and they can be quantified as long as there is enough experience to detirmine what measurements correllate with the sounds that we hear (poor Julian...).
If this is not obvious from the equipment that you have heard, it might be that that gear has its own weaknesses that have nothing to do with blanced operation. The reason I say this is that the legacy of 45 some odd years of hifi recordings is a rather massive testemony to the success of the technology. A few high-end audio failures are not suficient to be its defeat.
My advice is to listen to balanced gear that is done right, as I am sure you will agree that it is importanat to listen to single-ended gear that is done right for the same reason!
At least we both agree about Mr. Hirsch! |
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. |
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 |
