Interconnect Inductance vs. Capacitance

I have not asked Joseph at Audio Horizons for the specs on my Dimension cable yet. I will this weekend.

Greg,
I'm inclined to agree with you and retract my speculation. Certainly that's how a large concert venue would be set up. If I had some monoblocks instead of an integrated amp - I'd probably have be thinking more along this line. Minimizing cable lengths within the limits of equipment placement is always a good thing, but given you have a choice between length of ICs and length of speaker cables, putting the amps at the speakers would probably be the best choice for sound quality.

Hello again. Sorry that I was away with my other new toy...

I was a beta tester for a cable maker and tested about 10 versions of his ICs. This guy is quite interesting. He told me that he would never share any findings from his IC experiments with others. This is similar to a good friend of mine from Kansas. He makes the best BBQ that I have ever had. He told me that his grandpa would not pass the recipe to his own family until he was *very* ill...

My point is that EE courses only teach the basics. A lot of know-hows, tuning, refinement, and/or tweaking are the accumulation of experiences in the said field. Most companies' whitepapers most likely will not reveal their secret ingredients.

Bill, have you had the chance to find out the capacitance of your AH ICs? Note that Bill's configuration needs 5ft of ICs and mine needs 10ft. Bill's power amp is more sensitive and so his Dude preamp needs to have higher attenuations and thus lower output impedance. (Review Al's note about 75/25 vs. 50/50, using Thevenin's Theorem.) Consequently, the requirement for his setup is not as strict as mine.

Thanks all for the contribution.

Ric,

I can't really think of any good reference that would bring the scholarship which it sounds like the Ramos book contains to the subject of audio cables. My perception is that unfortunately most of the writing on the subject is in one of two opposing camps, neither of which is helpful. One being the camp which is well schooled in EE theory, but ignorant of high-end audio, and the other being the camp which believes in (or creates or promotes) the nonsense and quack science which pervades much of the cable marketing literature and other writings about high-end cables. Even the appeal of cables which undoubtedly (based on anecdotal indications) are really excellent performers, and worth their high cost, is spoiled for me by distaste for the white papers and other writings that are associated with them, which I am sufficiently schooled to know are nonsense.

If you've never seen it, you'll want to read this paper by Bill Whitlock of Jensen Transformers:

http://wiring.svconline.com/ar/avinstall_designer_cables_critical/index.htm

You won't agree with all of it, and I don't completely agree with everything he says, but he is a noted authority in the field, his products serve both the pro audio and high-end consumer audio markets, and this and some of the other papers on the Jensen site are the closest thing I've seen to writing about cables that is both knowledgeable and balanced (no pun intended).

Re speaker placement/room treatments, etc., Shadorne is very knowledgeable. I suggest that you research his posts in the Speaker category of the forum.

The debate about long/short interconnects/speaker cables is an old one, of course, with many previous threads here presenting differing opinions. My own feeling is that it is probably dependent on the particular components and cables, and on what is most synergistic with the overall sonic character of the system. My initial bias, in most cases, would be to err in the direction of having the speaker cables short, because of the higher currents that are involved and the low impedances that are needed. In my own system, physical placement considerations dictate that both preamp to power amp and power amp to speaker connections be about 6 to 8 feet.

I have no particular thoughts to offer about your cable experiments. Have fun!

And thanks for your good contributions to this thread.

Regards,
-- Al

Ric

I think you'd be better off with 2' between your pre-amp and your amp and 10' between your amp and your speakers. Do you have power amps integrated in your speakers?

With all due respect, I'd strongly recommend longer ICs with shorter spkr cabling.
The spkrs-wire-amp circuit is tricky enough as is without the added complexity of extra long wires.
Regards

"... and I need 10 ft of ICs between preamp and power amp."

So I gotta ask - why do you need 10' between pre-amp and power amp. I think you'd be better off with 2' between your pre-amp and your amp and 10' between your amp and your speakers. Do you have power amps integrated in your speakers?

Agree that if you are stringing your own cable - you gotta think a bit about impedances - resistance, inductance, and capacitance. And the requirements are different on the IC side than the speaker side.

Almarg/Redkiwi - this is a fun thread. I've been reading through Ramos "Fields and Waves in Communication Electronics" - and while it's a great source and touches on basic cable configs (co-ax/parallel) and covers electro-statics, Maxwell equations, impedance calculations, skin effects, and group delays, etc. at low and high frequency - it still doesn't quite make the jump to impacts on sonics. I'm looking for some good references on acoustics (room/speakers/etc.) as well as something that might deal with some more complicated cable geometries like for instance Litz twisted pairs, Litz helicals, or Litz counter helicals. CHELA?. Any info, references. (PS - I only have one BSEE degree - perhaps the emphasis is on the BS end).

Anyone playing with mag wire for ICs or speaker?

BTW - I've got some Neotech 3m NES-3001's and a 1.2m NEDV-1001 on order ( http://www.neotechcable.com/product.htm ). Unheard and unseen - but I'm a little psyc'ed (that in itself will make the cables sound better I'm told!). Will wait to hear before I consider the NEI-1001. System is - Oppo 983H -> CI Audio VDA-2 DAC -> Jeff Rowland Concerto Integrated (Note: No external distance between pre-amp and amp per comment above) -> Dali Euphonia MS-5. I was trying to avoid the cable game and jump from my $0.33/ft Home Depot 12 AWG OFC tri-wire to wire nut to dual 12 AWG to amp speaker cable - all with RS spades(heh - I needed something to hook up to the MS-5s in a pinch) to the end game - something that I'll not be thinking of replacing, if for monetary reasons only. Any thoughts? This is a leap of faith and perhaps a rather expensive gamble.

Gotta share this too - my speakers are tri-wired and the NES-3001 I'm getting is bi-wired (11 AWGx2x2 at speaker end). So I need jumpers for one of the poles. Lots of thoughts on what to do there - I'm leaning toward putting the bi-wire on the Treble/Mid and jumping to the low - better coherency by word of mouth, but nothing to support it given audio frequencies and lumped impedances. You might or might not believe what I'm putting ($) into these DIY jumpers - decided on Furutech FP-218R Spades cold krimped to 18AWG Neotech cryro treaded wire with 10 strands to get 8AWG effective. Why? Because you can for one? And Rhodium sure does look like silver even if it's not. But second, thinking that the NES-3001 is 8 AWG (about 17AWGx8 x2) and if I decide bi-wire is myth - I'm running an 8 AWG cable and just will need two more jumpers for the tri-wire.

Tell me I'm nuts.

Vett93

My higher capacitance Audio Horizons IC's sound better from my Dude pre to Samson amps then the much lower capacitance Blue Jeans IC.

No rolling off of the highs at all with the AH IC's. They are simply more full bodied and refined sounding while retaining all the highs and air in my system.

The Blue Jeans cable only cost $39 and they were still very good indeed. Anyone looking for a great cable for very little money - the Blue Jean is a great choice.

Seems my TRL Dude and Samsons like the AH cables better - at least to my ears. Again, the highs were not rolled off at all.

Bill

You were right, Al, as Thevenin was on your side. :-)

It is the parallel of the two resistors that determines the output impedance. Good memory!!

Cheers!

Shadorne's example of dynamic and lively sound is a good one. I am not sure what electric characteristics can be used to describe it.

I am not sure either but I suspect it has to do with the current drive capabilities of the output stage of the line level component. I have observed it many times and it is quite audible on long runs of say 30 feet or more. If the current is insufficient to drive the higher capacitance of long interconnects then the slew rate of the signal will be less (at least that would be my guess)

Vett93 -- It's been too long since I studied Thevenin's Theorem. It looks like I was right, and bandwidth will be greater when the attenuator is set for 12db attenuation, compared to when it is set for 6db attenuation.

The Thevenin equivalent circuit for the preamp output with the attenuator set for 6db, at the mid-point of its resistance range (what I've referred to as "50K/50K"), is a voltage source equal to one-half of the voltage being applied to the attenuator, in series with 25K.

The Thevenin equivalent circuit for the preamp output with the attenuator set for 12 db attenuation (what I've referred to as "75K/25K"), is a voltage source equal to one-quarter of the voltage being applied to the attenuator, in series with 18.75K.

Therefore the higher attenuation setting will result in a lower source impedance, resulting in a smaller RC time constant and a wider bandwidth.

-- Al

The interactions between human and machine are always fascinating to me. A lot of them are beyond textbooks. Shadorne's example of dynamic and lively sound is a good one. I am not sure what electric characteristics can be used to describe it.

I also think that a system is only as good as its weakest point. In my example, if I get a pair of ICs that have higher capacitance, it can never sound good in my system. This is, of course, assuming that I still have good hearing.... lol...

A fellow Dude preamp owner likes the top line model from Audio Horizons the best. AH's website states the higher end models have higher capacitance. This seems odd to me. He is testing Blue Jeans Cables' ICs now. It will be interesting to see what he thinks....

Mathematics R us! lol...

LOL here too! As someone who also has multiple EE degrees, albeit one fewer than you do, this thread is definitely fun!

Agreed on the 6db, given your power amp's relatively low sensitivity. But I also chose 12db for my example in order to simplify my other comments (the references to 25K and 75K), which would have been harder to present if the impedances looking into the preamp output would have been 50K in both directions (to ground and to the signal source).

If you think 6dB attenuation is not enough, a higher level of attenuation will actually lower the 3dB freq. A higher level of attenuation means that you will have a larger R value in series with the output. So at a lower sound volume, the highs will be rolled off even more and yields a narrower bandwidth!

This would be true if the attenuator were simply a variable resistor in series with the output.

But I've been assuming (correct me if I'm wrong) that the end terminals of the attenuator are connected, respectively, to some signal source within the preamp (which itself is assumed to have negligible output impedance), and the preamp's ground. And that the preamp output is the wiper of the attenuator, with the output being referenced to preamp ground.

Given that, and using my 12 db example, the presence of the 25K in parallel with the cable capacitance makes for a very different situation than simply having some fraction of the 100K in series with the output. Without the capacitance, you get 12db at all frequencies. With the capacitance, you get a frequency-dependent voltage divider ratio equal to the combined impedance of the parallel combination of the 25K and 255pf (combined vectorially), divided by that figure plus 75K.

I'm not sure without doing some further analysis if that would result in greater bandwidth or less bandwidth than at a 6db attenuation setting (a 50K/50K setting on the attenuator, instead of 75K/25K). Note that in both cases, the capacitance is not being charged toward the source voltage. It is being charged toward some lower voltage, through an overall impedance which is not simply the resistance between the output terminal and the "top" end of the attenuator. In the 50K/50K case, the overall output impedance is 25K. In the 75K/25K case, the overall output impedance is only 18.75K. But of course the 25K is to ground, while the 75K is to the voltage source.

To use a wonderful expression I read in a completely different context a while back, my mind is becoming a bit too "pretzeled" by all of this to readily see the answer :)

Regards,
-- Al

Thanks Al for the comments. Let me further clarify two points.

If you think 6dB attenuation is not enough, a higher level of attenuation will actually lower the 3dB freq. A higher level of attenuation means that you will have a larger R value in series with the output. So at a lower sound volume, the highs will be rolled off even more and yields a narrower bandwidth!

The 2nd point is that my power amp needs 4V RMS to achieve full power, 100W/8ohm. The preamp has 12dB of gain. Most CD players have max outputs between 1V-2V. So the 6dB setting assumption is quite appropriate for my setup. I usually set the volume control knob anywhere between 10 to 3 o'clock, and I don't listen very loud....

Mathematics R us! lol...

Shadorne -- Thanks for your observations. I just want to make sure it's clear to everyone that my previous post was written before I saw your last post, and was in response to the prior posts, not to your good observations.

Regards,
-- Al

I agree with Vett's calculations, and the 12.5kHz answer. When I said that interconnect capacitance could become "marginally significant" under extreme circumstances, I was thinking of source components with active output stages. For passive preamps, or preamps with unbuffered resistive attenuators at their output, the effect can obviously be more than "marginal."

Audioquest4life, not sure where you are going wrong with your math, but for 100 ohm output impedance and 196pf capacitance, the 3db bandwidth would be:

1/(2*3.14*(100)*(196exp-12)) = 8,124,269 Hz (i.e., 8.1 MHz)

For Vett's example, it would be:

1/(2*3.14*(50000)*(255exp-12)) = 12,489 Hz

Although of course the 50K assumption is something of an oversimplification, and in practice I think the answer might not be quite that bad. The 50K output impedance assumes the control is set for 6db attenuation, and is the total impedance looking back into the output. But, first, I would think the control typically would be set for greater than 6db attenuation. Let's call it 12db, which would mean 25K between the output terminal and ground, and 75K between the output terminal and the preamp's internal voltage source which drives the attenuator. The high frequency rolloff would be determined, in this example, by the voltage divider ratio formed by the parallel combination of the 255 pf and the 25K, and the 75K. I'm not going to bother trying to figure that out, but my suspicion is that the net result would be a somewhat wider bandwidth than what would be provided by the 50K assumption. In any event, the 50K assumption does seem like a reasonable rough ballpark, which makes the point that the treble rolloff can be significant.

Regards,
-- Al

No, as far as I am aware no one sells interconnects with capacitance high enough to "grossly" affect high end frequency response. But under extreme circumstances (high component output impedance, long cable length, high cable capacitance per unit length), it could become marginally significant. So in that sense it is potentially a system-level issue, that the consumer should be aware of.

For less than 6 foot IC's no worries but once you get to 12 feet or more then you would be surprised at how poorly some RCA line level gear will perform. I don't think the high end roll off is the most noticeable - to me there often seems to be a loss of dynamics when using very long runs - I'd avoid long RCA runs and go with XLR balanced if that is your need.

Can you please chart the numbers you used, my calculations are different then yours. I used 1/2*3.14*100 or 50*255), neither one of the impdencance vlaues match your solution. I got 20017.5

Using the same forumula, and for my system, I have 14 foot cables, but a low 14pf per foot for a total 196Pf, Neotech UPOCC cables, preamp has 100ohm output impedance and the amps are 210 kOhm input impedance.

The numbers read: 1/(2*3.14*100*196)= 30772

I think my math is off some, Thanks.
Audioquest4life

Thanks all for the great comments. I understand that the capacitance and the inductance are not the whole picture for most high-end audio gears. Like what I said earlier, I have a preamp that uses a 100K attenuator at the output and I need 10 ft of ICs between preamp and power amp.

Let me use an example to illustrate my point. Take Cardas Golden Cross ICs as an example. According to its website, the capacitance is 25.5 pF/ft. For 10 ft ICs, it yields 255pF.

Since the preamp attenuator has 100K max resistance, let's assume 50K ohm output impedance. With these two numbers, let's compute the 3dB roll-off freq, Fc.

Fc = 1/(2*Pi*R*C) = 12.5 KHz

As you can see, the highs are significantly rolled in this configuration! Hope it all makes more sense now.

Just out of curiousity, do you think that anyone selling cables has IC designs that would exhibit enough capacitance to grossly affect high end frequency response? Isn't this more an issue for the designer than the consumer?

No, as far as I am aware no one sells interconnects with capacitance high enough to "grossly" affect high end frequency response. But under extreme circumstances (high component output impedance, long cable length, high cable capacitance per unit length), it could become marginally significant. So in that sense it is potentially a system-level issue, that the consumer should be aware of.

Thanks for your very comprehensive and well done earlier post, btw.

Regards,
-- Al

Just out of curiousity, do you think that anyone selling cables has IC designs that would exhibit enough capacitance to grossly affect high end frequency response? Isn't this more an issue for the designer than the consumer?

Regarding the 500K input impedance, a common-cathode tube input stage can indeed have high input impedance levels. If you measure the resistance between the grid and the cathode of a tube, it is in the order of several mega ohms or higher. To lower it to 500K, one would need to put grid resistors to get that level.

Another concept to clarify is that it is the output impedance of the preamp that can cause the roll-off highs, instead of the input impedance of the power amp. This is because the capacitance of the ICs and the preamp output impedance form a low pass filter.

Regarding the experiments with two capacitors, the smaller value ones are actually the higher end model. The smaller ones are Mundorf Silver/Gold & Oil, and the larger ones are Mundorf M Caps.

TRL told me that they had experimented various capacitance levels of the same brand and same model of capacitors. Their findings were similar to mine. If you look at the Dude preamp, you will be amazed by the size of the output coupling caps.

Good responses by all. Yes, I too was wondering about the 500K -- that seems unusually high, and I would imagine that parasitic impedances in the circuit could become significant relative to that value, at least at high frequencies. But more significantly, I suspect that Vett's capacitor experiment is most likely a good example of what Redkiwi was referring to when he said:

One of the problems in science is that when experimenting you need to assume certain variables are not relevant in order to observe the impacts of an experiment on what you believe to be relevant. You cannot screen out all other variables all of the time.

My guess would be that the differing results with the two capacitors were not the result of the different capacitance values (the variable being tested), but were the result of differences in the departure of each device from being an ideal capacitor. Dielectric absorption, ESR (equivalent series resistance), leakage, stray inductance, and other known and unknown parameters make every capacitor something other than a pure capacitor. Which is why it is fairly widely recognized that different makes of capacitor, of the same values, can sound different, especially when they are in the signal path.

Redkiwi, I certainly agree that digital cables can sound different in an audio system. It is fairly widely documented, both in this paper and in threads at this and other audio forums, that 1.5 meters is an optimal length for cd transport to dac connections, and significantly shorter lengths will increase jitter by causing the round-trip timing of reflections from the dac input, and re-reflections from the transport output, to be such that the re-reflection would arrive coincident with edges of the original waveform. Of course, the degree of that effect would be dependent on the degree of impedance mismatch at both ends, as well as on the rise and fall times of the transport output, and the jitter reduction capability of the dac (if any).

Re skin effect, I haven't performed or studied in detail any analysis of its relevance to audio frequencies, but based on what I have read I would not disagree that it could be marginally relevant in some cable configurations.

I do still feel, though, that inductance and characteristic impedance are not relevant to analog audio interconnect cables of reasonable length, particularly in the bass region. When you say

If the characteristic impedance of the cable is below the output impedance of the upstream component then phase errors can get audible, particularly in the bass, and is a major cause of the belief that interconnects can be system dependent.

my feeling is that something else must have been going on to account for the differences your testing revealed. Of course, as I noted previously, inductance certainly can be expected to be a significant factor in a speaker cable (as opposed to an interconnect, where source and load impedances are much higher than for a speaker interface). And since characteristic impedance is a function of inductance (and capacitance), there may be an indirect correlation between speaker cable characteristic impedance and performance, but not in the usual sense of impedance mismatch resulting in vswr effects.

Regards,
-- Al

I think in the end the best approach is to design for minimum capacitance AND minimum inductance (as well as minimum resistance). That is the approach I took when designing my interconnect cables. http://forum.audiogon.com/cgi-bin/fr.pl?fcabl&1243691470&openmine&zzRova&4&5#Rova

Of course it is not possible to do so perfectly and you must alway balance the compromises you must make. Ideally you want to pass the signal from one end of the cable to the other without loss, or change in any way.

As I said I tried my best to make the optimal balance of compromises while attempting to meet all requirements. I think I have made an interconnect that is on the right track. I'm very pleased with the results. (So are a few others who have built cables from my design).

ROVA

Let me give an example to illustrate my point. I had a DIY preamp project recently. I used 0.68uF for the output coupling caps. Since my power amp has an input impedance of 500K, it yields 0.5Hz 3db cut-off freq. Then I changed the output caps to 10X value; i.e., 6.8uF. The 3dB freq. is now 0.05Hz. Interestingly, I can hear better bass. A couple friends can hear that too.

Interesting. 500K is pretty high for input impedance. Did you ensure their was a return path for input bias current on the power amp? (Charge can build up in coupling caps if you aren't careful)

My point is that there often is theory. It is just that we don't always consider it relevant to the particular context, and it turns out it is.

In the case of the larger cap - it is possible that more bass extension reduced group delay, but it is also possible the larger cap released energy more slowly, smearing the signal slightly and giving the impression of greater weight. One therefore needs to experiment to confirm what is happening.

I wasn't referring so much to my interconnects when referring to skin effect ideas that are floating around. Some of the ones I find interesting are those being talked about by Supra and LessLoss, for example. With cable experiments I very rarely use any measuring equipment other than the ears of a listening panel so specs aren't possible.

A gap between theory and reality is that there is no theory (that I am aware of) explaining how human being would perceive various specs in high end audio. I have never seen any EE courses relating human perception and technical specs in any length of details, even after my 3 EE degrees.

Let me give an example to illustrate my point. I had a DIY preamp project recently. I used 0.68uF for the output coupling caps. Since my power amp has an input impedance of 500K, it yields 0.5Hz 3db cut-off freq. Then I changed the output caps to 10X value; i.e., 6.8uF. The 3dB freq. is now 0.05Hz. Interestingly, I can hear better bass. A couple friends can hear that too.

I am not sure that there is any theory that can explain it!

Back to ICs. Redkiwi, your postings are interesting. Can you tell us the specs of your ICs after you improved the skin effect?

Thanks.

Hi Al. I should disclose that I am a cable designer and so you can accuse me of being a snake oil salesman now (insert smiley face here - I am taking a shot at myself, not at you). But responding to your point. One of the problems in science is that when experimenting you need to assume certain variables are not relevant in order to observe the impacts of an experiment on what you believe to be relevant. You cannot screen out all other variables all of the time. This leads the electrical engineering field to have certain beliefs - such as the one you have expressed, that many issues in transmission theory don't apply at audio frequencies for short cables. That is fine for the EE that simply wants to make something work. To optimize a system, it is not good enough. In pushing the envelope to develop better audio cables many/most designers I know revisit what the typical EE assumes away as irrelevant, and tests whether indeed it makes a difference. A good case in point these days is skin effect. Most EEs I know that are not working in high end audio will assume skin effect is an irrelevant issue for audio frequencies, and yet there are many of us designing cables who have found otherwise, and many designs are specifically targeted at dealing with skin effect in various ways today. Another example is in the area of digital cables, where one of the smartest designers I know, Dan Lavry, has at least once stated his belief that using a correct impedance cable is not relevant for short lengths of a meter or so, yet most digital cable designers have found otherwise. Using absolute beliefs is a necessary part of life, or we would be hopelessly confused. But testing for how those absolutes are really shades of gray is necessary for some innovations to occur. When I design, I just try different things. When I hear an effect, I search for a theory that might explain it. Armed with a possible theory, I then conduct an experiment to see if in fact using the theory to predict the outcome of different iterations proves to be useful. If it does then it adds to the mix of theories I use to optimize a cable's performance. In the vast majority of cases the theories that I use are accepted theories, just not normally considered to be relevant at audio frequencies for short cables. I suspect we are wandering far from the OP's interests, my apologies to the OP.

Redkiwi -- Interesting post. But I think it should be pointed out that many, and I would venture to say most, people with relevant technical knowledge (who are not manufacturers of certain high-end cables) would disagree with some of your statements about characteristic impedance.

Characteristic impedance, being part of what are called "transmission line effects," is (at least for typical interconnect lengths) generally considered to be utterly inapplicable to audio frequencies. Note that I limited the statements in my first post above to cables carrying analog audio, not digital signals, video, or rf.

And I am at a loss to see how, even if there were some significance at audio frequencies, phase errors in the bass would result from impedance mismatch.

I do agree that pickup of high frequency noise might, in the hypothetical case of a cable that is both unshielded and unbalanced, be influenced by impedance mismatch between cable and source component. However, noise rejection is best addressed, and is usually addressed, by quality shielding and, in the case of balanced interconnections, by common mode rejection.

Regards,
-- Al

For an interconnect, there is no question you want low capacitance or the treble begins to roll off, coupled with group delay. The group delay can have a significant effect on the subjective impression of speed and dynamics of much of the music spectrum. But inductance is another matter. Inductance in an interconnect is really only relevant in that it affects the characteristic impedance of the cable. In an ideal world the characteristic impedance of an interconnect would be at, or slightly above, the output impedance of the upstream component. If the characteristic impedance of the cable is below the output impedance of the upstream component then phase errors can get audible, particularly in the bass, and is a major cause of the belief that interconnects can be system dependent. If the characteristic impedance of the cable is too far above the output impedance of the upstream component then it can act as an antenna and pick up noise and fine detail will be lost or obscured. With no standard for output impedance for audio components then one of the challenges for a designer of interconnects is how to minimize the problems of impedance mismatches. Some claim to have effectively eliminated this problem with their designs.

I just got a set of Blue Jean cable IC's to run between my $4000 preamp and $5500 amps. The LC-1 cost me $38 shipped for a 5 foot set. Do the math folks....they sound very good and I will let you know more once they are burned in more.

For a twisted pair design, the capacitance and the inductance are a function of the distance between the conductors relative to their diameters and are somewhat inversely related. The closer the conductors the less inductance and the more capacitance. The further apart, the more inductance and the less capacitance. For instance, a lot of ICs might have a pair of conductors that helix around a core that keeps them at some distance in order to achieve a certain design point (this is just twisted pair from a design point). Similarily, the thickness of the insulation itself can keep the conductors separated at some distance in a twisted pair that does not have a 'core'. The capacitance is also related to the type of dielectric used (or more specifically, the effective relative permitivity of the dielectric that the conductors experience). There are other cable geometries that are used that will tend to push the impedances one way or another. In general, all of the impedances (resistance, capacitance, inductance) scale linearly with the length of cable so shorter is better if you want to minimize impedances.

It's probably easiest to try to get the vendor's specs on what impedance a given cable exhibits - if they've bothered to measure them. Measuring inductance and capacitance typically requires a pretty good (expensive) piece of equipment. Low capacitance and low inductance are both desirable, but since you usually hurt one to help the other, going two far in either direction tends to be a mistake. However, I agree with Almarg that capacitance is a bigger factor for ICs while inductance (and resistance) is generally a bigger factor for speaker cables due to the differences in the amount of current involved between the two (e.g. harder for a low current system to charge a capacitance while harder for a high current system to overcome inductance).

Other things that are reputed to affect the "sound" of cabling are the purity of the conductor (e.g. OFC (99.99%), UPOCC (99.9999%), solid conductors supposedly better than stranded conductors, the type of conductor (copper, silver, silver coated copper), effective cross section of total conductors (more cross section, less DC resistance), diameter of individual insulated conductors (smaller gauge wires show less variation in internal impedance with frequency (due to skin effect, DC travels through the entire conductor - higher frequencies move to the outsides of the conductor - so some vendors will say you should have, for instance, a number of smaller gauge conductors (say 8 x 21 AWG) rather than one large conductor (say 1 x 12 AWG) for speaker cables), surface of conductor (smooth/polished is better), the type of dielectric (actual physics here that affects capacitance), the geometry of the conductors within the cable , the mechanical stability of the conductors (e.g. damping and isolation), how well the connector or wire makes contact with the terminals (e.g. type of plating on connectors, type of metals in connectors, surfaces of connectors, contact points of connectors, contact enhancement treatments, oxidation on connectors, vibrations in connectors, etc.), shielding from RFI and EM radiation (more important on ICs due to low voltages and currents and subsequent application of the noise through your amplifier), and various types of conditionings like cryogenic freezing. However, there is great controversy over which, if any, of these types of things has an impact on the 'sound' or whether "great" sound can be achieved with a 'budget' cable.

To be honest, most cables spec's are not going to be a problem from an electrical standpoint - unless perhaps your amp is sensitive to highly capacitive loads (most are designed not to be) or you are running at lot more than say 8 feet of cable. And most of the cable specs are not going to tell you something that will indicate whether it sounds better or worst to you in your system. Even if the cable were to have characteristics that introduce frequency distortion - perhaps you like attenuated highs on your ICs because your gear is bright for instance.

However, most audio folks say that they hear differences between different cable's sounds. Most differences in cables' sounds are 'subtle' and perhaps a matter of taste. To me, it seems to be a bit of a hit or miss operation if you are just looking at 'spec's. It's not clear what measured parameters are important to the "sound" and there's a lot of marketing hype about various other characteristics that are hard to substantiate. If you can actually audition some cables and you like one better than the other - and you feel that the difference in cost justifies the improvement, then go for it - though this could lead to a potentially un-ending cable upgrade path if you have unlimited time and resources. The next best source is likely to be discussion forums of other folks experiences with various cables on various types of equipment (particularly the ones where they decided to go from cable x to cable y).

Keep in mind that some cables reportedly require some period of time to settle into how they will ultimately sound. If you believe in breakin (another controversy), the periods typically indicated for this transition tend to be on the order of a few days to a week or two of active (24x7) use, depending on a number of factors - though most likely related to the type of dielectric. If you are trying to compare two cables - that is also a bit of a dicey operation. Try to keep all other variables constant. Same gear, same room, same speaker placement, same relative placement of listener to the speakers. It may take you some time of listening before you decide that a particular sound is to your liking - what might sound like more definition at first might end up seeming harsh after a while. So it may take more than just flipping back and forth a few times to get to a lasting impression of whether you really like one sound versus the other. Also keep in mind that your listening room may have a much larger effect on the sound of your system than the cables so if that's out of control - perhaps you're better off focusing on that first before you start trying to 'tune in' your cables. Another rule of thumb quoted would be to not spend more than about 10-20% of your system's cost on cabling. If you are spending more that on cabling, you might be better off buying better gear than better cables.

Not much help here, but a lot of things to consider perhaps. From what I'm seeing, seems like perhaps a bit too focused on the capacitance vs inductance issue as the title suggests. Try measuring more with your ears than your impedance meter. However, if you are interested in some more of the technical side, this might be helpful - http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/Analog.html

The Cable company offers only standard length cables for loan. They also charge 10% of the list price of the cables as the fees.

I do have various 1M ICs and I have tried them between the CDP and preamp. I do hear differences among them and I like the Reality Cables the best. But, the difference between Reality Cables and BJC 1M ICs is quite subtle.

The Reality Cables use a twisted pair design for the ICs, which would increase the capacitance. It works great with a short 1M run and the CDP which has a low output impedance. I am not sure that it would work well for the Dude preamp and at a longer length.

I have tried Anti-Cable's speaker cables. I know that they have a lot of fans. But they don't work well in my setup. I heard some artifical coloring to the sound which was un-natural to my ears.

You can try cables through The Cable Company for a fee. I did that once but don't remember the cost. It wasn't much.

I've had cables from Harmonic Technology then Cardas Neutral Reference. I tried Blue Jeans 3 meter balanced and could not hear a difference between them and the Cardas. I sold the Cardas. Then I bought some Speltz 3 meter balanced that I'm currently using. I think they might sound a bit better than the BJC in my system but it is very subtle. I highly recommend Blue Jeans Cable. They are so reasonably priced, the people there seem to know a lot about cables and are so free of hype - they just tell it like it is. I found it refreshing.

Interestingly, TRL told me that Blue Jeans Cables RCA interconnects are good enough. Paul may be right as these BJC ICs have the lowest capacitance that I can find anywhere! This man has integrity!!

TRL's cables are not cheap though. So I am exploring all options. It would be great if manufacturers can offer in-home trial. Then I'll find out if they can beat BJC's $50 10-ft ICs. :-)

Call TRL and get a set of their interconnects. The Dude will easily drive these cables, which in their own right are very good. These cables were the original design behind the FIM/CRL cables. The only drawback is they are heavy and somewhat inflexible, but the sound more than makes up for it.

One could share to others how to measure inductance, capacitance, and resistance if they have a Digital Volt Meter. And explain the differences when apply to power cords or speaker cables.

Common VOM's (volt-ohm-milliameters), whether digital or analog, can measure resistance directly. Some digital vom's also have the ability to measure capacitance. There are also separate instruments specifically designed to measure capacitance. I am not aware of any low-cost instruments that will measure inductance, although there may be some.

I had said that inductance is insignificant for interconnects carrying analog audio signals. But it may be significant in a speaker cable, if the inductance is particularly high, as a result of the cable being long and/or the inductance per unit length of the particular cable being high. In which case it would attenuate the treble somewhat (inductance attenuates or blocks high frequencies).

Unusually high capacitance in a speaker cable can cause some amplifiers to operate out of their comfort zone, or to become unstable. It will not, however, produce the kind of high frequency roll-off I described for interconnect cables, because the output impedance of a power amplifier is vastly lower than the output impedance of a line-level component.

As for power cords, obviously sufficient gauge (meaning low enough resistance) is required to support the maximum amount of current that may be drawn through it. Beyond that, my opinion is that we enter the realm of metaphysics (definition: "a priori speculation upon questions that are unanswerable to scientific observation, analysis, or experiment"), and anecdotal evidence of differences is about all we can expect.

Regards,
-- Al

One could share to others how to measure inductance, capacitance, and resistance if they have a Digital Volt Meter.
And explain the differences when apply to power cords or speaker cables.

I recently changed the preamp, from BAT VK-3iX to the Dude from TRL. I also had to get a new pair of RCA ICs between preamp and amp, as the new preamp is single ended and the previous preamp used balanced connections.

So I got a 10ft pair of Blue Jeans RCA interconnects. They seem to work fine. Another owner of the Dude preamp suggested the top line model from Audio Horizons. Their website indicated that the cable capacitance went higher and higher with their higher end models. This does not give me a warm and fussy feeling to try them.

The Dude preamp has extremely high output impedance, as the volume control is at the output. The volume attenuator has a max resistance around 100K! So I am reluctant to use ICs with higher capacitance for the reasons Al stated.

Thoughts are welcome.

PS. The Dude preamp sounds very very good even with the high output impedance.

Al has given you great advice. Another source of info on this topic is from the Blue Jean Cable website.

Assuming you are referring to analog ic's carrying audio frequencies (as opposed to ic's carrying digital signals or other high frequency signals such as video), inductance is likely to be insignificant.

High capacitance may cause the highs to be rolled off, particularly if the component driving the cable has a high output impedance. That is because the output impedance of the driving component and the capacitance of the cable form a low pass filter, having a bandwidth corresponding to the product of the output impedance and the capacitance.

It is true that some very high-end cables have highish capacitance. That is one example of how some high-end cables are designed to be non-neutral. It is also an example of how cable performance can be system-dependent, because the effects of the capacitance will be dependent on component output impedance.

Regards,
-- Al

High capacitance can be a tough load for consumer grade gear - best to stick to short runs or low capacitance IC's. You can lose dynamics and in some extreme cases you get distortion.