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Comparing the tone of three different "boutique" cables
- Thread starter bongomania
- Start date
My grandfather was an audiophile and I inherited some of his equipement which included some ultra super high end cables from his stereo. Since I had no use for them I sold them on Ebay with no reserve just see what would happen. I think I got something like $800 for a bunch of 15 year old Norstar cables. I couldn't believe it! Here is an interesting article I have found on this issue (mostly above my head, and WAY out of my price range) Enjoy!
Having read some of the recent comments on several of the Internet audio groups, concerning audible differences between interconnect and loudspeaker cables, I could not resist adding some thoughts about the subject as a concerned engineer possessing credible credentials.
To begin, several companies design and manufacture loudspeaker and interconnect cables which they proudly claim possess optimized electrical properties for the audiophile applications intended. However, accurate measurements of several popularly selling cables reveal significant differences that call into question the technical goals of their designer. These differences also question the capability of the companies to perform accurate measurements of important cable performance properties. For example, any company not possessing a precision C-L-R bridge, a Vector Impedance Meter, a Network Analyzer, a precision waveform and impulse generator, wideband precision oscilloscopes, etc., probably needs to purchase them if they are truly serious about designing audio cables that provide premium performance.
The measurable properties of loudspeaker cables that are important to their performance include characteristic impedance (series inductance and parallel capacitance per unit length), loss resistance (including additional resistance due to skin-effect losses versus frequency), dielectric losses versus frequency (loss tangent, etc.), velocity-of-propagation factor, overall loss versus frequency into different impedance loads, etc.
Measurable properties of interconnect cables include all of the above, with the addition of those properties of the dielectric material that contribute to microphonic noise in the presence of ambient vibration, noise, etc. (in combination with a D.C. off-set created by a pre-amp output circuit, etc.).
While competent cable manufacturers should be aware of these measurements and the need to make them during the design of their cables, the raw truth is that most do not! Proof of this can be found in the absurd buzzard-salve, snake-oil and meaningless advertising claims found in almost all magazine ads and product literature for audiophile cables. Perhaps worse, very few of the expensive, high-tech appearing cables we have measured appear to have been designed in accordance with the well-known laws and principles taught by proper physics and engineering disciplines. (Where are the costly Government Consumer Protection people who are supposed to protect innocent members of the public by identifying and policing questionable performance claims, misleading specifications, etc.?) --- Caveat Emptor!
For example, claiming that copper wire is directional, that slow-moving electrons create distortion as they haphazardly carry the signal along a wire, that cables store and release energy as signals propagate along them, that a final energy component (improperly labeled as Joules) is the measure of the tonality of cables, ad nauseum, are but a few of the non-entities used in advertisements to describe cable performance.
Another pet peeve of mine is the concept of a special configuration included with a loudspeaker cable which is advertised as being able to terminate the cable in a matter intended to deliver more accurate tonality, better imaging, lower noise, etc. The real truth is that this special configuration contains nothing more than a simple, inexpensive network intended to prevent poorly-designed amplifiers, with a too-high slew-rate (obtained at the expense of instability caused by too much inverse-feedback) from oscillating when connected to a loudspeaker through a low-loss, low-impedance cable. When this box appears at the loudspeaker-end of a cable, it seldom contains nothing more than a Zobel network, which is usually a series resistor-capacitor network, connector in parallel with the wires of the cable. If it is at the amplifier-end of the cable, it is probably either a parallel resistor-inductor network, connected in series with the cable conductors (or a simple cylindrical ferrite sleeve covering both conductors). But the proper place for such a network, if it is needed to insure amplifier stability and prevent high-frequency oscillations, is within the amplifier - not along the loudspeaker cable. Hmmm!
Having said all this, are there really any significant audible differences between most cables that can be consistently identified by experienced listeners? The answer is simple: very seldom! Those who claim otherwise do not fully grasp the power of the old Placebo-Effect - which is very alive and well among even the most well-intentioned listeners. The placebo-effect renders audible signatures easy to detect and describe - if the listener knows which cable is being heard. But, take away this knowledge during blind or double-blind listening comparisons and the differences either disappear completely or hover close to the level of random guessing. Speaking as a competent professional engineer, designer and manufacturer, nothing would please me and my company's staff more than being able to design a cable which consistently yielded a positive score during blind listening comparisons against other cables. But it only rarely happens - if we wish to be honest!
Oh yes, we have heard of golden-eared audiophiles who claim to be able to consistently identify huge, audible differences between cables. But when these experts have visited our facility and were put to the test under carefully-controlled conditions, they invariably failed to yield a score any better than chance. For example, when led to believe that three popular cables were being compared, varying in size from a high-quality 12 AWG ZIP-CORD to a high-tech looking cable with a diameter exceeding an inch, the largest and sexiest looking cable always scored best - even though the CABLES WERE NEVER CHANGED and they listened to the ZIP Cord the entire time.
Sorry, but I do not buy the claims of those who say they can always audibly identify differences between cables, even when the comparisons are properly controlled to ensure that the identity of the cable being heard is not known by the listener. We have accomplished too many true blind comparisons with listeners possessing the right credentials, including impeccable hearing attributes, to know that real, audible differences seldom exist - if the comparisons are properly implemented to eliminate other causes such as system interactions with cables, etc.
Indeed, during these comparisons (without changing cables), some listeners were able to describe in great detail the big differences they thought they heard in bass, high-end detail, etc. (Of course, the participants were never told the NAUGHTY TRUTH, lest they become an enemy for life!)
So why does a reputable company like DAL engage in the design and manufacture of audiophile cables? The answer is simple: since significant measurable differences do exist and because well-known and understood transmission line theory defines optimum relationships between such parameters as cable impedance and the impedance of the load (loudspeaker), the capacitance of an interconnect and the input impedance of the following stage, why not design cables that at least satisfy what theory has to teach? And, since transmission line theory is universally applied, quite successfully, in the design of cables intended for TV, microwave, telephone, and other critical applications requiring peak performance, etc., why not use it in designing cables intended for critical audiophile applications? Hmmm! To say, as some do, that there are factors involved that competent engineers and scientists have yet to identify is utter nonsense and a cover-up for what should be called pure snake oil and buzzard salve - in short, pure fraud. If any cable manufacturer, writer, technician, etc. can identify such an audible design parameter that cannot be measured using available lab equipment or be described by known theory, I can guarantee a nomination for a Nobel Prize.
Anyway, I just had to share some of my favorite Hmmm's, regarding cable myths and seemingly fraudulent claims, with audiophiles on the net who may lack the technical expertise to separate fact from fiction with regard to cable performance. I also welcome comments from those who may have other opinions or who may know of something I might have missed or misunderstood regarding cable design, theory or secret criteria used by competitors to achieve performance that cannot be measured or identified by conventional means. Lets all try to get to the bottom of this mess by open, informed and objective inquiry.
I sincerely believe the time has come for concerned audiophiles, true engineers, competent physicists, academics, mag editors, etc. to take a firm stand regarding much of this disturbing new trend in the blatantly false claims frequently found in cable advertising. If we fail to do so, reputable designers, engineers, manufacturers, magazine editors and product reviewers may find their reputation tarnished beyond repair among those of the audiophile community we are supposed to serve.
Having read some of the recent comments on several of the Internet audio groups, concerning audible differences between interconnect and loudspeaker cables, I could not resist adding some thoughts about the subject as a concerned engineer possessing credible credentials.
To begin, several companies design and manufacture loudspeaker and interconnect cables which they proudly claim possess optimized electrical properties for the audiophile applications intended. However, accurate measurements of several popularly selling cables reveal significant differences that call into question the technical goals of their designer. These differences also question the capability of the companies to perform accurate measurements of important cable performance properties. For example, any company not possessing a precision C-L-R bridge, a Vector Impedance Meter, a Network Analyzer, a precision waveform and impulse generator, wideband precision oscilloscopes, etc., probably needs to purchase them if they are truly serious about designing audio cables that provide premium performance.
The measurable properties of loudspeaker cables that are important to their performance include characteristic impedance (series inductance and parallel capacitance per unit length), loss resistance (including additional resistance due to skin-effect losses versus frequency), dielectric losses versus frequency (loss tangent, etc.), velocity-of-propagation factor, overall loss versus frequency into different impedance loads, etc.
Measurable properties of interconnect cables include all of the above, with the addition of those properties of the dielectric material that contribute to microphonic noise in the presence of ambient vibration, noise, etc. (in combination with a D.C. off-set created by a pre-amp output circuit, etc.).
While competent cable manufacturers should be aware of these measurements and the need to make them during the design of their cables, the raw truth is that most do not! Proof of this can be found in the absurd buzzard-salve, snake-oil and meaningless advertising claims found in almost all magazine ads and product literature for audiophile cables. Perhaps worse, very few of the expensive, high-tech appearing cables we have measured appear to have been designed in accordance with the well-known laws and principles taught by proper physics and engineering disciplines. (Where are the costly Government Consumer Protection people who are supposed to protect innocent members of the public by identifying and policing questionable performance claims, misleading specifications, etc.?) --- Caveat Emptor!
For example, claiming that copper wire is directional, that slow-moving electrons create distortion as they haphazardly carry the signal along a wire, that cables store and release energy as signals propagate along them, that a final energy component (improperly labeled as Joules) is the measure of the tonality of cables, ad nauseum, are but a few of the non-entities used in advertisements to describe cable performance.
Another pet peeve of mine is the concept of a special configuration included with a loudspeaker cable which is advertised as being able to terminate the cable in a matter intended to deliver more accurate tonality, better imaging, lower noise, etc. The real truth is that this special configuration contains nothing more than a simple, inexpensive network intended to prevent poorly-designed amplifiers, with a too-high slew-rate (obtained at the expense of instability caused by too much inverse-feedback) from oscillating when connected to a loudspeaker through a low-loss, low-impedance cable. When this box appears at the loudspeaker-end of a cable, it seldom contains nothing more than a Zobel network, which is usually a series resistor-capacitor network, connector in parallel with the wires of the cable. If it is at the amplifier-end of the cable, it is probably either a parallel resistor-inductor network, connected in series with the cable conductors (or a simple cylindrical ferrite sleeve covering both conductors). But the proper place for such a network, if it is needed to insure amplifier stability and prevent high-frequency oscillations, is within the amplifier - not along the loudspeaker cable. Hmmm!
Having said all this, are there really any significant audible differences between most cables that can be consistently identified by experienced listeners? The answer is simple: very seldom! Those who claim otherwise do not fully grasp the power of the old Placebo-Effect - which is very alive and well among even the most well-intentioned listeners. The placebo-effect renders audible signatures easy to detect and describe - if the listener knows which cable is being heard. But, take away this knowledge during blind or double-blind listening comparisons and the differences either disappear completely or hover close to the level of random guessing. Speaking as a competent professional engineer, designer and manufacturer, nothing would please me and my company's staff more than being able to design a cable which consistently yielded a positive score during blind listening comparisons against other cables. But it only rarely happens - if we wish to be honest!
Oh yes, we have heard of golden-eared audiophiles who claim to be able to consistently identify huge, audible differences between cables. But when these experts have visited our facility and were put to the test under carefully-controlled conditions, they invariably failed to yield a score any better than chance. For example, when led to believe that three popular cables were being compared, varying in size from a high-quality 12 AWG ZIP-CORD to a high-tech looking cable with a diameter exceeding an inch, the largest and sexiest looking cable always scored best - even though the CABLES WERE NEVER CHANGED and they listened to the ZIP Cord the entire time.
Sorry, but I do not buy the claims of those who say they can always audibly identify differences between cables, even when the comparisons are properly controlled to ensure that the identity of the cable being heard is not known by the listener. We have accomplished too many true blind comparisons with listeners possessing the right credentials, including impeccable hearing attributes, to know that real, audible differences seldom exist - if the comparisons are properly implemented to eliminate other causes such as system interactions with cables, etc.
Indeed, during these comparisons (without changing cables), some listeners were able to describe in great detail the big differences they thought they heard in bass, high-end detail, etc. (Of course, the participants were never told the NAUGHTY TRUTH, lest they become an enemy for life!)
So why does a reputable company like DAL engage in the design and manufacture of audiophile cables? The answer is simple: since significant measurable differences do exist and because well-known and understood transmission line theory defines optimum relationships between such parameters as cable impedance and the impedance of the load (loudspeaker), the capacitance of an interconnect and the input impedance of the following stage, why not design cables that at least satisfy what theory has to teach? And, since transmission line theory is universally applied, quite successfully, in the design of cables intended for TV, microwave, telephone, and other critical applications requiring peak performance, etc., why not use it in designing cables intended for critical audiophile applications? Hmmm! To say, as some do, that there are factors involved that competent engineers and scientists have yet to identify is utter nonsense and a cover-up for what should be called pure snake oil and buzzard salve - in short, pure fraud. If any cable manufacturer, writer, technician, etc. can identify such an audible design parameter that cannot be measured using available lab equipment or be described by known theory, I can guarantee a nomination for a Nobel Prize.
Anyway, I just had to share some of my favorite Hmmm's, regarding cable myths and seemingly fraudulent claims, with audiophiles on the net who may lack the technical expertise to separate fact from fiction with regard to cable performance. I also welcome comments from those who may have other opinions or who may know of something I might have missed or misunderstood regarding cable design, theory or secret criteria used by competitors to achieve performance that cannot be measured or identified by conventional means. Lets all try to get to the bottom of this mess by open, informed and objective inquiry.
I sincerely believe the time has come for concerned audiophiles, true engineers, competent physicists, academics, mag editors, etc. to take a firm stand regarding much of this disturbing new trend in the blatantly false claims frequently found in cable advertising. If we fail to do so, reputable designers, engineers, manufacturers, magazine editors and product reviewers may find their reputation tarnished beyond repair among those of the audiophile community we are supposed to serve.
I had never heard those claims.... I think I will use them the next time the hardware at work is acting up! "I think some slow moving electrons are plugging up the wires! Let's give them a short burst of 24V to get them moving again!"
Or, you can bait them along by rubbing some cheese or peanut butter on the receiving end of the cable.
Bob Lee (QSC)
In case you missed it, I work for QSC Audio!
- Jul 3, 2001
- 12,668
- 2,036
- 67
- Disclosures
- Former Technical Communications Developer, QSC Audio
It's not the complementary signals that give you CMR in a balanced connection but equal impedances to ground.
It's not the complementary signals themselves but the way they are treated on the receiving end. The noise picked up by the two lines tends to be the same, and the signals from the two lines are mixed in reverse polarity (what some call "out of phase"), so that the noise cancels. The matched impedance to ground is so that the induced noise on the two lines is of the same magnitude - also important for canceling.
Say, while I've got you EE's on the line, let me ask some advice about using transformers to change the z in and z out of my test rig. If I used a 1:15 step-up at the output of my audio converter, making the 50 ohm z out appear to be 11.25K; and if I used a 2:1 step-down at the input, making the 1M z in appear to be 250K; and connected the cables under test from one xfo to the other; would that be a reasonable way of making the cables perform as though they were connected from an instrument with 11K z out to an amp with 250K z in?
i only use superconducting Pb wires to connect my instrument to my amp. i have to keep it in a bath of increasingly expensive liquid helium at all times while playing, and i can't touch it as it's toxic, but, damn, the low end from those cooper pairs! 
I would try and keep away from transformers. Although you can achieve the impedance changes you are looking for you are also adding more variables - frequency response and phase shift as well yet more expense. Good quality transformers are not going to be cheap.
Simulating a 250k load (from 1M) can be easily achieved by a adding resistor in parallel with the input of your measuring device so the combined value is 250k. (R=330k approx).
Putting a resistor in series with the output of your audio converter is similarly going to alter the impedance presented to the cable. You would have to take measurements at the cable end of the resistor though and not use any indications from your audio source.
The output impedance of a guitar varies considerably depending on whether it is active or passive and the settings on the volume if active*, and tone and pickup configurations if passive. So your figure of 11k sounds fairly arbitrary and I assume is for an 11k pickup, passive, tone and volume at max. Once you back the volume off the impedance rises rapidly.
Far be it from me to say how you should conduct your tests but I would be inclined to do them at several values of source impedance, say 50 ohms which is close-ish to an active with volume at max**. 11k for passive at max and would also cover an active backed off, and a higher figure to represent a backed of volume of a passive say 100k. Just my 0.02
*I have never come across a preamp where the volume pot is on the input, they are usually on the output but there no doubt is somewhere.
**There will be large variations on this figure depending on preamp design and components.
You have to remember that you could come under very close scrutiny and much criticism, especially if you find that there are minimal differences between cables. (Some people claim they can hear a bat f@rt at 300 yards.)
Hope this helps.
You might be just simplifying it a bit (and I'm not sure I'll be making it LESS confusing) but the way I understand balanced connections, it seems you left out a few key parts.
First, the "complementary signals" have to be treated on both ends, not just the receiving end. Balanced connections take a signal, split it in two, reverse the phase on one line, send those two lines (+ground) through the cable, and then reverse one line's phase again on the other side before mixing the two lines to recreate the signal. So the polarity actually gets reversed twice. Mixing a signal with it's direct inverse (out of phase) cancels it out. If you just mixed the two signals without "re-flipping" the phase, you'd end up with nothing BUT the noise.
Signal "a" becomes A and -A on the cable. Noise comes in giving you A+N and -A+N. Then on the other end you flip it back, so -A+N becomes A-N. This converts the reversed line back to the original signal, AND reverses the phase of the noise on that line, so now you're mixing (A+N) and (A-N) getting A+A. N and -N cancel each other out.
So part of the magic in combating noise over a balanced connection is this signal split-flip-flip-mix process, which requires balancing circuitry on both ends, which is in the connected gear, NOT in the cable. An extra wire doesn't help this happen unless you're connecting a balanced output to a balanced input.
There may be other side-effects (which may or may not be beneficial) from using extra wires, twisted pairs, etc. in a normal non-balanced connection (like good ol' 1/4" instrument cables), but AFAIK the impact on noise is nowhere near that of a balanced connection.
Anyhow, hope this makes sense....
Benjamin Strange
Commercial User
- Dec 25, 2002
- 9,737
- 310
- 49
- Disclosures
- Owner / Tech: Strange Guitarworks
Cool, you're the second guy to suggest just using resistors instead of more fancy circuits/systems/gadgets, so I am glad to have reinforcement of such a cheap and easy solution. Just so I have a clear picture, would a resistor in parallel to the input connect straight from signal to ground, or would it connect at both ends to the signal wire?
Since an active bass into a hi-z amp input has approximately the same z-in and z-out as my audio converter in/outputs, it is no trouble to do the measurements at those z's, but what people have pointed out (and my graphs seem to indicate) is that one of the main purposes/effects of that wide z in/out range is to minimize the effects of cable loading--thus minimizing any measurable differences between cables, to the point that my graphs may be insufficiently meaningful.
So while I agree that from one scientific standpoint I should test at a range of z's, from another it may be most meaningful to limit my tests to the worst-case scenario. However that does mean I should also test at a z out much higher than 10 or 11K!
Oh believe me, I know this all too well.
Bob Lee (QSC)
In case you missed it, I work for QSC Audio!
- Jul 3, 2001
- 12,668
- 2,036
- 67
- Disclosures
- Former Technical Communications Developer, QSC Audio
It's really not as complicated as all that. The essential thing about a balanced interconnection is that the receiving end (the input) is differential and the two input legs have equal impedances to ground.
The signal itself can be symmetrical--and typically would be if the source is a transformer-coupled output or a circuit where the signal on one leg is derived from the other through an inverter. But the signal doesn't actually have to be symmetrical; many completely effective balanced outputs have one leg driven by active circuitry and the other coupled to ground through an impedance equal to the driven leg's output impedance.
There are advantages and disadvantages to each approach, but the net result is the same: the receiving end is sensitive to differential-mode signal voltage and rejects common-mode; the audio signal on the line is differential, while the noise picked up is (primarily) common-mode; and so the receiving end responds to the differential signal and not to the common-mode noise.
Bob Lee (QSC)
In case you missed it, I work for QSC Audio!
- Jul 3, 2001
- 12,668
- 2,036
- 67
- Disclosures
- Former Technical Communications Developer, QSC Audio
I too would model impedances using resistors instead of transformers. The input Z of a typical input for a passive instrument is very high--often around 1 MΩ--and usually almost entirely resistive. You can experiment with different input impedances by shunting different resistances to ground.
Probably the best emulation of a passive pup's output Z is what you've already been using: a pup in series with the test signal source's output.
Probably the best emulation of a passive pup's output Z is what you've already been using: a pup in series with the test signal source's output.
Bongo
I was in two minds whether to suggest using a pickup as a source impedance (I missed the fact that you are using one in this rather long post). Having played about with pickups I know just how much they vary, you would need a pretty good one as the cheaper ones have a very limited response (but that's another can of worms). I know you are trying to simulate a cable in it's working environment so there is a lot to be said for using a pickup.
The load resistor resistor would just connect across signal and ground, in parallel with the input of your measuring device.
I was in two minds whether to suggest using a pickup as a source impedance (I missed the fact that you are using one in this rather long post). Having played about with pickups I know just how much they vary, you would need a pretty good one as the cheaper ones have a very limited response (but that's another can of worms). I know you are trying to simulate a cable in it's working environment so there is a lot to be said for using a pickup.
The load resistor resistor would just connect across signal and ground, in parallel with the input of your measuring device.
