Re: He's all yours
And that means that it doesn't?
Why is it that I must support my claims with a complete technical treatise, yet you expect them to be dismissed entirely simply with a wave of your hand? If my claims haven't any veracity, how does your hand-waving have any greater veracity? Where is your physics, engineering, measurements or anything of substance?
As always, I'm perfectly willing to accept being wrong. So help me out here, Fred.
Take a balanced output that's outputting two signals each of the same magnitude and the same phase. With this, drive a symmetrical coil of wire, such as a typical voicecoil. How exactly does any appreciable amount of current come to flow through that coil of wire?
I don't see how any appreciable amount of current could flow, which would indicate an appreciably high common-mode impedance.
It's an established fact that symmetrical transformer windings have exceedingly high common-mode impedances (which is why their common-mode rejection is high even with unbalanced sources). How is a symmetrical coil of wire called a voicecoil any different fundamentally than a symmetrical coil of wire called a transformer winding?
C'mon, Fred. If what I'm saying is due to nothing but the darkness of ignorance, how 'bout shedding a little illumination on the subject instead of hand-waving?
And what shred of evidence have you offered thus far that I have no idea what I'm talking about? How is your hand-waving, without adding so much as a photon of illumination to the subject any less pretentious and posturing?
Ah. So all you have to do is claim you know enough to see it's total nonsense? What evidence do you have to offer to support that? This looks to be nothing but pretentious posturing to me.
How does one learn anything from someone who refuses to shed any light on the subject and simply dismisses with the wave of his hand?
If you truly know enough to know that it's total nonsense, then you should be able to explain why it's nonsense, using the same physics, engineering, measurements or anything else of substance that you expect from me. Or do you exempt yourself from your own set of standards?
Just as you expect others to swallow your hand-waving?
When you offer nothing other than hand-waving, what other motiviation is there but either spite or your own pointless posturing?
se
Fred Dieckmann said:
And that means that it doesn't?
Why is it that I must support my claims with a complete technical treatise, yet you expect them to be dismissed entirely simply with a wave of your hand? If my claims haven't any veracity, how does your hand-waving have any greater veracity? Where is your physics, engineering, measurements or anything of substance?
As always, I'm perfectly willing to accept being wrong. So help me out here, Fred.
Take a balanced output that's outputting two signals each of the same magnitude and the same phase. With this, drive a symmetrical coil of wire, such as a typical voicecoil. How exactly does any appreciable amount of current come to flow through that coil of wire?
I don't see how any appreciable amount of current could flow, which would indicate an appreciably high common-mode impedance.
It's an established fact that symmetrical transformer windings have exceedingly high common-mode impedances (which is why their common-mode rejection is high even with unbalanced sources). How is a symmetrical coil of wire called a voicecoil any different fundamentally than a symmetrical coil of wire called a transformer winding?
C'mon, Fred. If what I'm saying is due to nothing but the darkness of ignorance, how 'bout shedding a little illumination on the subject instead of hand-waving?
And what shred of evidence have you offered thus far that I have no idea what I'm talking about? How is your hand-waving, without adding so much as a photon of illumination to the subject any less pretentious and posturing?
Ah. So all you have to do is claim you know enough to see it's total nonsense? What evidence do you have to offer to support that? This looks to be nothing but pretentious posturing to me.
How does one learn anything from someone who refuses to shed any light on the subject and simply dismisses with the wave of his hand?
If you truly know enough to know that it's total nonsense, then you should be able to explain why it's nonsense, using the same physics, engineering, measurements or anything else of substance that you expect from me. Or do you exempt yourself from your own set of standards?
Just as you expect others to swallow your hand-waving?
When you offer nothing other than hand-waving, what other motiviation is there but either spite or your own pointless posturing?
se
"I don't see how any appreciable amount of current could flow, which would indicate an appreciably high common-mode impedance."
Yes exactly!
In this post:
http://www.diyaudio.com/forums/showthread.php?postid=246851#post246851
You state:
"Asymmetrical crossovers do, yes. Stick an inductor or capcitor on just one line. That line will no longer have the same impedance with respect to ground as the other line. That will unbalance the line and result in mode conversion from common-mode to differential, reducing common-mode rejection.
Which is it?
And before you answer both, why is a symmetrical crossover required, inspired, or desired? Can you hear it? Can you measure it? Is there something that causes a speaker to have a low enough common mode impedance to make this anything but an abstract argument with no understood measurement or mechanism for common mode impedance in a loudspeaker.
Transformers have measured common mode rejection ratios. Based on real measurable and physical properties like interwinding capacitances that couple the common mode signal to the secondary and provide a mechanism for conversion to a differential signal. This does not seem analogous to a mechanism that would exist in a loudspeaker.
The only asymmetrical crossovers I have heard about, refer the highpass and lowpass filters having different order crossover slopes.
http://www.google.com/search?hl=en&...ssive+speaker++crossovers+&btnG=Google+Search
Yes exactly!
In this post:
http://www.diyaudio.com/forums/showthread.php?postid=246851#post246851
You state:
"Asymmetrical crossovers do, yes. Stick an inductor or capcitor on just one line. That line will no longer have the same impedance with respect to ground as the other line. That will unbalance the line and result in mode conversion from common-mode to differential, reducing common-mode rejection.
Which is it?
And before you answer both, why is a symmetrical crossover required, inspired, or desired? Can you hear it? Can you measure it? Is there something that causes a speaker to have a low enough common mode impedance to make this anything but an abstract argument with no understood measurement or mechanism for common mode impedance in a loudspeaker.
Transformers have measured common mode rejection ratios. Based on real measurable and physical properties like interwinding capacitances that couple the common mode signal to the secondary and provide a mechanism for conversion to a differential signal. This does not seem analogous to a mechanism that would exist in a loudspeaker.
The only asymmetrical crossovers I have heard about, refer the highpass and lowpass filters having different order crossover slopes.
http://www.google.com/search?hl=en&...ssive+speaker++crossovers+&btnG=Google+Search
You're verging dangerously close to agreeing with me. A speaker is a two terminal device. That means that "symmetry" within it is irrelevant to drive, cabling, whatever- a two terminal speaker or load, no matter what's inside of it, how it's arranged, how symmetrical or unsymmetrical it is, automatically has 100% common mode rejection.
All the talk about symmetrical voice coils, mechanics, center of the coil wrt to ground, ad nauseum, is irrelevant. It all adds up to some Z, and you can arbitrarily call Z the sum of two series elements of Z/2 each. Unless superposition is somehow violated, in which case one or two of us is headed for Stockholm next year to pick up a Nobel.
Side Q: Do any of you guys ever sleep?
Balanced or unbalanced?
In my opinion and in my experience, as long as distances between power amp and speakers is short (less than 10 meters) and the output impedance of the amp is low (as it always is), you should not have any improvement by going balanced on the interconnects. That is putting the power amps closer to the speakers or inside the speakers themselves.
Again: as long as impedance is low, power drive high and distances short you will probably do worst by using balanced interconnects becase a new variable would enter the picture.
The balancing/unbalancing interface would add two more stages, or at least one if the amp can be directly wired balanced at its input.
My experience on this area was, many years ago, using quality low impedance dynamic balanced mics wired as unbalanced to feed a low impedance mic input on a Uher portable recorder. Cables up to 10 m wold not introduce noise or pick RF.
Considering this combination as perhaps one of the worst you could find, if you think of the low level mic signal, might suggest that a power amp/speakers interface is quite a different beast.
Of course I'm looking at all this from a win/lose point of view. IMHO.
Carlos
In my opinion and in my experience, as long as distances between power amp and speakers is short (less than 10 meters) and the output impedance of the amp is low (as it always is), you should not have any improvement by going balanced on the interconnects. That is putting the power amps closer to the speakers or inside the speakers themselves.
Again: as long as impedance is low, power drive high and distances short you will probably do worst by using balanced interconnects becase a new variable would enter the picture.
The balancing/unbalancing interface would add two more stages, or at least one if the amp can be directly wired balanced at its input.
My experience on this area was, many years ago, using quality low impedance dynamic balanced mics wired as unbalanced to feed a low impedance mic input on a Uher portable recorder. Cables up to 10 m wold not introduce noise or pick RF.
Considering this combination as perhaps one of the worst you could find, if you think of the low level mic signal, might suggest that a power amp/speakers interface is quite a different beast.
Of course I'm looking at all this from a win/lose point of view. IMHO.
Carlos
the sky wouldn't be safe
some of the questions earlier talk about commode mode rejection so I will follow the same line of argument here.
a speaker generates output (sound) when there is a voltage drop across its two termianls (or more precisely there is a current going through its coil). If you inject the same signal on both terminals, there will not be any voltage drop or current through the coil, thus no sound (output).
Doesn't that seem like an amp with perfect common mode rejection?
Fred Dieckmann said:
some of the questions earlier talk about commode mode rejection so I will follow the same line of argument here.
a speaker generates output (sound) when there is a voltage drop across its two termianls (or more precisely there is a current going through its coil). If you inject the same signal on both terminals, there will not be any voltage drop or current through the coil, thus no sound (output).
Doesn't that seem like an amp with perfect common mode rejection?
Hi,
The problem with " a little bit of oxide " on the surface of a copper wire is that it does not stop oxidizing.So the little oxidation becomes a lot of oxidation given time.
Within that context, yes, in the long run I do believe a gastight insulator would be preferable over other types of insulation.
PVC as an insulator is worse as it contains agressive chemicals (chlorides) that when combined with oxygen attack the surface of the wire.
If you insist on telling the world that copperoxide is nothing to worry about in audio, then yes, I do object against such blanket statement.
That's comparing apples and oranges.
If induced noise rides on the speaker cable it usually comes from the source already.
NOT picked up by the speaker cable itself.
If you're suspecting a worst case scenario and want some protection against this just use a simple twisted pair as a speakercable.
The added capacitance can upset some SS amps but in most other cases this should work just fine.
Cheers,
The problem with " a little bit of oxide " on the surface of a copper wire is that it does not stop oxidizing.So the little oxidation becomes a lot of oxidation given time.
Within that context, yes, in the long run I do believe a gastight insulator would be preferable over other types of insulation.
PVC as an insulator is worse as it contains agressive chemicals (chlorides) that when combined with oxygen attack the surface of the wire.
If you insist on telling the world that copperoxide is nothing to worry about in audio, then yes, I do object against such blanket statement.
That's comparing apples and oranges.
If induced noise rides on the speaker cable it usually comes from the source already.
NOT picked up by the speaker cable itself.
If you're suspecting a worst case scenario and want some protection against this just use a simple twisted pair as a speakercable.
The added capacitance can upset some SS amps but in most other cases this should work just fine.
Cheers,
fdegrove said:If you insist on telling the world that copperoxide is nothing to worry about in audio, then yes, I do object against such blanket statement.
Cheers,
isn't there a materiality test here? Sure, the oxidation will impact sound in theory, just as zillions of neutrinos passing throughthe earth each day. Yet, I haven't heard of anyone trying to sheld their gears from neutrinos.
Unless you can present data suggesting that oxidation will generate audible differences, it is best to assume that we cannot hear it.
if we cannot hear it, why worry about it?
Fred Dieckmann said:
Yes exactly? Just a moment ago you were saying that I hadn't offered anything of any substance to indicate that a loudspeaker driver has even slightly significant common-mode impedance. Now I say that it would be quite high and you say "yes exactly!"?
What did I miss here?
Which is it between what two choices?
I was never arguing that it was something to lose sleep over. But given the things that many audiophiles here routinely do lose sleep over, it's hardly out of proportion.
And what do you mean by no understood measurement or mechanism for common-mode impedance in a loudspeaker?
What a lot of crap!!!!!
A guy asked a reasonable question. We gave him some suggestions. Then, on post 18, we switched to techno-babble that has nothing to do with the original question.
The poor guy is so confused that he has probably given up, sold his stereo, and taken up photography as a hobby.
And why is this......? Only one guy can answer, and I fear that he might. Again. Still. Some more.
Jocko
A guy asked a reasonable question. We gave him some suggestions. Then, on post 18, we switched to techno-babble that has nothing to do with the original question.
The poor guy is so confused that he has probably given up, sold his stereo, and taken up photography as a hobby.
And why is this......? Only one guy can answer, and I fear that he might. Again. Still. Some more.
Jocko
time out
Gentlemen, I can appreciate the engineering banter regarding balanced speakers and the extrapolations hereof, but I still am not clear as to the best or better yet most, common way of wiring my system. Thanks to those who have offered a suggestion or solution. If this helps, my Adcom has the following specs:
balanced output: >1200ohms
unbalanced output >600ohms
output: 1.0V
The suggestion of trying both is a reasonable one except if interconnects are less desirable, I would have invested in 3m cables that wouldnt be used. This is the main reason I was asking for counsel. BTW, I havent built the GCs yet, and since starting this thread, I found that there is a thread dealing specifically with a balanced GC (design is posted) Could this help?
All things considered, if interconnects, unbalanced, </= 3m should be fine, this saves me a set of speaker wires, since they would require two pair, rather than one pair of interconnects and also the added hassle of balance amps and XO.
With so many people with active speakers and monster monoblocs sitting out in the room, I though this was going to be a quick "who wants to give this guy the obvious answer" sort of thread.
amt
Gentlemen, I can appreciate the engineering banter regarding balanced speakers and the extrapolations hereof, but I still am not clear as to the best or better yet most, common way of wiring my system. Thanks to those who have offered a suggestion or solution. If this helps, my Adcom has the following specs:
balanced output: >1200ohms
unbalanced output >600ohms
output: 1.0V
The suggestion of trying both is a reasonable one except if interconnects are less desirable, I would have invested in 3m cables that wouldnt be used. This is the main reason I was asking for counsel. BTW, I havent built the GCs yet, and since starting this thread, I found that there is a thread dealing specifically with a balanced GC (design is posted) Could this help?
All things considered, if interconnects, unbalanced, </= 3m should be fine, this saves me a set of speaker wires, since they would require two pair, rather than one pair of interconnects and also the added hassle of balance amps and XO.
With so many people with active speakers and monster monoblocs sitting out in the room, I though this was going to be a quick "who wants to give this guy the obvious answer" sort of thread.
amt
Well now according to this I'm the last person who said anything lucid. Now there's a first.
Oh, yah, IMHO, 1200 ohm is kinda high for a a balanced output impedance. 600 is OK if you feel like you really need to do a current match balanced line. Current matching kind of makes sense (as Ive heard it argued) if you live across the street from a 50 Kw radio station. Otherwise voltage matching makes more sense where your balanced output would be between 50 and 150 ohms.
Re: time out
I would be seriously surprised if you can pick up significant noise with such a set up, even with poor cable shielding.
a lot of the discussions here are theorietical, with next to zero bearing in reality. People like to show off their knowledge and self-perceived "sophistication" once in a while,, at the expense of making a fool out of themselves.
amt said:
I would be seriously surprised if you can pick up significant noise with such a set up, even with poor cable shielding.
a lot of the discussions here are theorietical, with next to zero bearing in reality. People like to show off their knowledge and self-perceived "sophistication" once in a while,
, at the expense of making a fool out of themselves.I give up
You are not going to answer any questions. You are going to keep being evasive. You make up new terms everytime you post. I will leave it for the one person in ten thousand who believes you have ANYTHING to say. discussion with you.I've things to do with people on THIS planet today. Maybe you can make up some new imaginary topics since you have run this around in circles till we are all bored to tears.
"I was never arguing that it was something to lose sleep over."
Not necessarily.
You *could* be arguing in your spare time.
You are not going to answer any questions. You are going to keep being evasive. You make up new terms everytime you post. I will leave it for the one person in ten thousand who believes you have ANYTHING to say. discussion with you.I've things to do with people on THIS planet today. Maybe you can make up some new imaginary topics since you have run this around in circles till we are all bored to tears.
"I was never arguing that it was something to lose sleep over."
Not necessarily.
You *could* be arguing in your spare time.
Attachments
1200 ohms????
That does sound high. I suppose that if each output was 600 ohms, then that would be the case. Really can't see why that would be so.
Maybe in all this techno-babble, I missed what amt considers as "long" to begin with. That could have short-circuited a lot of this nonsense.
BTW.....amt......did you read the Jensen papers showing the right and wrong way to do balanced??
Jocko
That does sound high. I suppose that if each output was 600 ohms, then that would be the case. Really can't see why that would be so.
Maybe in all this techno-babble, I missed what amt considers as "long" to begin with. That could have short-circuited a lot of this nonsense.
BTW.....amt......did you read the Jensen papers showing the right and wrong way to do balanced??
Jocko
fdegrove said:
Actually the oxide layer forms a protective barrier against further oxidation. So unless it's heated to high temperatures, or in some highly corrosive atmosphere, you're not going to lose any appreciable amount of copper. Hell, the exposed copper in the AC wiring of my house which is over 50 years old only has a slightly red patina.
Copper oxide is gas tight. And far far thinner than any practical plastic type insulation.
All I can say is that I haven't found it to be anything to worry about nor have I seen any evidence that it would be anything to worry about. At least not within a period of a century or so.
The whole issue about balanced interfaces IS about noise induced into the line.
A simple twisted pair is only helpful if the interface is balanced. If it's unbalanced, then about all the twisted pair can do is not add any further imbalance.
What added capacitance?
se
Audio cables typically use copper wire as a conductor because copper is inexpensive, pliable, and a good electrical conductor. However, copper oxidizes when exposed to air, forming copper oxide. This material is a poor conductor, which can cause a cheaply made cable or connection to degrade in performance over time.
http://emusician.com/ar/emusic_good_connections/
"A simple twisted pair is only helpful if the interface is balanced. If it's unbalanced, then about all the twisted pair can do is not add any further imbalance."
Reducing the area of the antenna loop is a very effect method of reducing magnetic pickup and there are many ways in which it may be achieved. The simplest and most effective loop area minimization strategy is to use twisted wire pairs. If the field is localized the pitch of the twist need to be fine (say one twist per centimeter) and conversely for wide area fields the pitch can be coarse (one twist permeter). Twisted wires works by local cancellation. The wires form a local antenna loop, but after the next twist the loop is inverted so a voltage with the opposite polarity is generated. This will cancel the voltage from the first loop. The use of shielded or coaxial cable is not as effective as one may think. In theory the loop area of coaxial cable could be considered as zero, but this ignores the asymmetrical way in which the induced current tends to flow in the shield. The best solution is to use shielded twisted pairs. If twisted pairs are not possible then the signal conductors should be located physically as close together as possible. Loop area minimization is a good general principal to follow. It reduces a systems susceptibility to electromagnetic fields and also reduces possible emissions of electromagnetic energy.
Varying magnetic fields will induce a varying current into a measuring circuit. These are far more troublesome than electrically coupled voltages because the current tends to flow regardless of the circuit impedance and magnetic shielding is very expensive. The magnitude of the induced current is proportional to the magnetic field strength, the rate at which it changes and the area of pickup loop in the measuring circuit.
Solutions:
Minimize measurement circuit area.
Use twisted pair cables.
Use mu-metal shielding if affordable.
Place measurement circuit away from magnetic fields.
Avoid moving or vibrating magnetic materials near measurement circuit.
Tied down cables to prevent vibration.
http://www.capgo.com/Resources/Measurement/Noise/Magnetic.html
Noise induced by varying magnetic fields will be differential and not rejected by a balanced circuit, which rejects common mode noise.
Noise Reduction Techniques in Electronic Systems, 2nd Edition by Henry Ott and Grounding and Shielding Techniques by
Ralph Morrison are excellent text on noise pickup as well.
http://www.book-reviews.info/Electronics_Book_Reviews/0471850683.shtml#review2
"What added capacitance?"
For the same length cable, twisting the wire will require a great length of the straight wire before it is twisted, than a straight run of wire for the same finished cable length. The shortest distance between two point is a straight line. If you have X pF per foot times a greater length, the capacitance increases.
http://emusician.com/ar/emusic_good_connections/
"A simple twisted pair is only helpful if the interface is balanced. If it's unbalanced, then about all the twisted pair can do is not add any further imbalance."
Reducing the area of the antenna loop is a very effect method of reducing magnetic pickup and there are many ways in which it may be achieved. The simplest and most effective loop area minimization strategy is to use twisted wire pairs. If the field is localized the pitch of the twist need to be fine (say one twist per centimeter) and conversely for wide area fields the pitch can be coarse (one twist permeter). Twisted wires works by local cancellation. The wires form a local antenna loop, but after the next twist the loop is inverted so a voltage with the opposite polarity is generated. This will cancel the voltage from the first loop. The use of shielded or coaxial cable is not as effective as one may think. In theory the loop area of coaxial cable could be considered as zero, but this ignores the asymmetrical way in which the induced current tends to flow in the shield. The best solution is to use shielded twisted pairs. If twisted pairs are not possible then the signal conductors should be located physically as close together as possible. Loop area minimization is a good general principal to follow. It reduces a systems susceptibility to electromagnetic fields and also reduces possible emissions of electromagnetic energy.
Varying magnetic fields will induce a varying current into a measuring circuit. These are far more troublesome than electrically coupled voltages because the current tends to flow regardless of the circuit impedance and magnetic shielding is very expensive. The magnitude of the induced current is proportional to the magnetic field strength, the rate at which it changes and the area of pickup loop in the measuring circuit.
Solutions:
Minimize measurement circuit area.
Use twisted pair cables.
Use mu-metal shielding if affordable.
Place measurement circuit away from magnetic fields.
Avoid moving or vibrating magnetic materials near measurement circuit.
Tied down cables to prevent vibration.
http://www.capgo.com/Resources/Measurement/Noise/Magnetic.html
Noise induced by varying magnetic fields will be differential and not rejected by a balanced circuit, which rejects common mode noise.
Noise Reduction Techniques in Electronic Systems, 2nd Edition by Henry Ott and Grounding and Shielding Techniques by
Ralph Morrison are excellent text on noise pickup as well.
http://www.book-reviews.info/Electronics_Book_Reviews/0471850683.shtml#review2
"What added capacitance?"
For the same length cable, twisting the wire will require a great length of the straight wire before it is twisted, than a straight run of wire for the same finished cable length. The shortest distance between two point is a straight line. If you have X pF per foot times a greater length, the capacitance increases.
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