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The Naked Truth about Interconnect Cables

[Italian version]

Oh no. Cables. Not that old HiFi chestnut again!
The naked truth about cables? It is simply, that all this cable nonsense is Bovine Excrement!
I am sure some of your initial reactions where like this.
To write about Cables anywhere is an open invitation to be barbecued. Flame-bait par excellence. Still, I'm going to talk about Cables. And not just any Cables, I'm going to talk about Interconnect Cables.
And I'm going to say that Interconnect Cables make a difference.
Do you start to question my sanity? Well, I better type fast, so I can get this all out before the men in white take me away.
Honestly, Cables make a difference. And "wrong "cables can make the wrong difference.
In my experience speaker cables make the greater difference, maybe because they are usually a lot longer. Interconnects do however still make a difference.
True, neither type of cable will make a huge difference. Swapping the cheap and nasty NE5532 Op-Amp in a CD-Player Output-Stage for a really nice one (like the AD811 or my favorite Nat Semi LM6172) makes more of an audible difference.
To get the ultimate from your system, you need the right cables.

So what's in a Cable?

Let's make a bold statement: "The best Cable is No Cable"
Let's make another one: "The Ideal Cable does not change the Signal traveling through it in ANY way."
Let's make a third one: "No Cable can improve the sound-quality of a system, they only make it worse in varying degrees."
And indeed, the best Cables I came across make things worse only a very little bit. The worst however....
I personally divide "effects" in audio into three "orders". These refer both to magnitude of effects and to the "obscurity" of the underlying principles.
First Order effects are those that produce massive and immediate changes to the sound. First Order Effects also mostly tend to have a direct, simple, logical and scientific explanation.
To elaborate, for interconnects capacitance is a first order effect. Use Goertz Interconnects (these are essentially unrolled capacitors) for a few meters and most sources will substantially roll off the treble due to the excessive Capacitance of the Cable.
Second Order effects make appreciable differences but are harder to pin down with logical explanations, though in most cases they exist and can be found.
To elaborate, the sonic difference between stranded cable, litz/hyperlitz cable and solid-core cable falls into this category, as does the dielectrical quality. Both matter quite a lot, but ultimately, if our cable has massive problems with First Order Effects any second order effects (for better or worse) will often be swamped out by these.
Third Order effects are way down and also, in many systems the resolution of the System is not high enough to seriously magnify the differences. In my own system I only begin to get a handle on third order effects.
I think the Conductor-material argument (silver vs. copper vs. plated copper vs. exotic conductors) falls into this category.

Cables have a sound!? How?

I have said; the ideal cable does not alter the signal.
Sound is a complex acoustic waveform, transformed into electrical signals at the time of recording. It is these signals that we want to keep as intact as possible.
We can describe these waveforms in terms of timbral, dynamic and temporal accuracy. All these have electrical equivalents. For my various bits of accuracy a lot of math is around to do it all scientifically. I personally prefer to stick to the "popular science" approach.
Accurate Timbres mean the a voice or instrument sound exactly as we would hear them normally. It includes both the harmonic structure (so no harmonic or intermodulation distortion please) and the basic frequency response.
Accurate Dynamics mean that the Dynamic Swing of the Signal (music) from the recording should not be reduced. Most Cables usually manage that (as they are passive devices).
Accurate Timing includes a few effects. There is some heavy math from Prof. Malcom Hawkesford on the Maxwell effect, which stipulates that different frequencies travel with different speed through a piece of wire. Then there are phase-effects from both the lowpass filter function of the cable and the skin effect.
Now all these effects listed above can usually be quantified in one way or the other, though it is rarely done and many of these measurements are still being treated as suspect by "mainstream" audio.
If we know what to measure we can easily analyse all first-order effects of the Cable. This simple electric's. We need to determine the complex Impedance of the cable, read all the capacitance's, resistance's and inductance's in the cable.
>From here on it gets fairly technical. If you just want to know which Cable I think sounds best and how to cheaply make yourself some, just go to Now for a bit of practical stuff.

The L, the C and the R

To alter the sound passing through it least, the various parts making up the impedance must have such values, that little or no alteration happens for Audio-frequencies. Interestingly, (for me) Audio-Frequencies means 4Hz - 100kHz in order to guarantee no more than 0.1db deviation at 20Hz or 20kHz.
If we look at the general impedance's in line-level interconnects, we find (usually) that the source-impedance is in the region of a few ohms to a few kilo-ohm. The load impedance ranges from about 10kOhm to about 1MOhm. The input capacitance is mostly very moderate too (100pF or less).
This provides us with some indication as to the relevance of the various electrical parameters that matter.
It seems that as long as the cable dc-resistance is being kept moderate (a few ohms) there will be little influence. The ratio between the cables resistance and the input resistance is very large. Indeed, the contact resistance of the RCA plugs used (terrible connector by the way) is often much larger.
A loop resistance of 1Ohm when feeding a 10kOhm Amplifier input will cause an attenuation of 0.001db.
The Cable inductance also matters little as long as it is kept moderate. The higher the load impedance is, the less relevant the Cable inductance becomes, the lower the load impedance is, the more relevant the cable inductance will become. Interconnect cables of about 1m (3') lengths rarely have an inductance of more than 1uH.
At 20kHz a 1uH inductor will have an impedance of about 0.13 Ohm, causing an additional -0.0001db attenuation.
Even with a 1nF input Capacitance in parallel with the 10kOhm Input Resistance (IEC Load) the attenuation by the Inductance is not significantly larger.
The Cable Capacitance is however crucial for interconnects. I hinted at that when I explained my "first order effects". The Capacitance to cause a -0.1db Roll-off at 20kHz with a 100 Ohm Source Impedance is about 15nF. If our source Impedance is however 1kOhm, a 1.5nF Capacitance will cause this roll-off.
I have seen Output impedance's of around 1kOhm in many pieces of mass produced Hi-Fi equipment. As the UK HiFi-Choice Magazine regularly prints Cable-Reviews that include technical sections with measurements, I can estimate the sort of maximal capacitance a cable may have. A capacitance of a few nF is easily accumulated on longer runs of various shielded cables, not to speak of the "unrolled capacitor" type Cables.
I would conclude that in line-level interconnection the DC-Resistance and Inductance of the cable are of purely academic interest. Constructions with significant resistance or inductance will likely not manipulate the sound of the signal passing through it in any significant way.
A capacitance as low as possible is however desirable. It seems also desirable to have the dielectric (read insulator) in the Cable to be of as good a Quality as possible.
Given my (and many other peoples) experiences with Capacitors, Teflon seems the best solid dielectric, while Air is even better. Polyethylene is also quite acceptable as dielectric while lesser plastics and specifically PVC are out.
Many commercial interconnect cables use PVC insulation.

EMI - all I heard a gentle HUUUUMMMMMMMMMMMMMM

Another one of my "first order effects" is of course the rejection of interference. This applies mostly to RFI but also lower frequency EMI can become a problem. The best rejection of external EMI and a good rejection of RFI seems to be achieved with woven constructions a'la Kimber and XLO.
Closely twisted Pairs are also good at rejecting EMI (about -47db for the best) but the degree of RF rejection is not as good and capacitance is high. Most current commercial "specialist" cables use this topology.
The worst for rejecting EMI and RFI is a "linear pair". Here simply two widely spaced wires are used. At the same time, I nevertheless had good success with this configuration.
Another way to reduce RFI (but not much EMI) is to shield the Cable. Shielded Cables do of course have their own problems in first and second Order effects (though not insoluble).
A variation on the shielded Pair is a cable where the shield also acts the "cold" conductor. These cables are known as co-axial cables and are the mainstay for Audio. The rejection of EMI in a coaxial cable is quite good. The cable that came packaged with your CD-Player is likely a coaxial cable.

To strand, or not to strand - that is the question here

(from Cabelitis, a very avantguard play - spoken by the Hero - the Son of an audio-cablemaker)
As we already mentioned second order effects, lets have a look at some other relevant ones.
In my experience all stranded Cables where each single conductor is made from several strands of copper that are not insulated from each other imparts an unpleasant harshness and brightness to the sound.
There are a few theories why this is so, if you want to read one of the more nutcake flavored ones, it comes from Ben Duncan. He proposes that copper-oxide forms between the strands that encourages non-linear conduction (little "mV" Diodes).
I shall keep out of this (there are pages full of letters on this in Wireless World), but as said I prefer solid conductors over stranded ones.
Litz-Style cables where each conductor is insulated from the others are usually much better or we can use single strands of solid core wire.
There is an argument that rectangular thin but wide conductors improve at the frequency extremes. Short of using Foil Tapes, one can use a few thin and round conductors (say 42 Gauge Magnet wire) run parallel, similar to the style of Cables from Nordost.
One more second order effect is the interaction of the signal current (as small as it is) with the shield. This will induce eddy currents in the shield that again will degrade the sound. Plenty of spacing helps but again, it reduces the effectiveness of the shielding.

Gold plated zirconium Cable in Carbon gels anyone?

Third order effects as said are mostly shrouded in mystery and I have not found much of handle yet. There are people that dislike silver-plated copper intensely. I have not found that myself, however. So there you just follow your ear or your guru.
There is the issue of conductor shape or diameter. All sorts of other neat little theories, including my own one.
I for example say, that immersing the raw conductor in specific oil which is produced from a very rare and highly poisonous snake found in the Brazilian rain forest (and long on the list of endangered species) will provide more "texture" to the music as well as more "bite" to violins. The immersion process needs to be undertaken by certified vestal virgins who are sacrificed to the Audio-God's after completing their task.
Unfortunately this is a very expensive process due to large numbers of native red Indian's who are bitten by the snakes when trying to collect them to get the oil as well as the large number of snakes needed to provide a small measure full of this precious oil. Also vestal virgins are getting kind'a rare (have I used them up too?). So do not expect an industrial application anytime soon.
But I'm sure it works.
Just believe me and buy my cable.
It's a tad bit expensive, but you see, all the payoff's of the widows, orphans, virgins parents and so on....

© Copyright 1998 Thorsten Loesch

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