Interconnect Frequency Response

DonH50

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I decided to play around with interconnects just a little. Mathematically, that is!

First, I checked a number of preamp, amp, and AVR specs (tube and solid state, from Pioneer to Krell and Audio Research) and found a range of around 20 kohms to 100 kohms input resistance, and none of them specified capacitance. I thought about assuming a 1 MHz input bandwidth, but that was 500 to 1000 pF or so which seemed a little high, so I picked 100 pF. Output impedances of the preamps ranged from around 200 ohms to 500 ohms or so, and with 1 MHz bandwidth the output capacitance is about 3 pF.

I used a couple of interconnects: a pretty standard 75-ohm cable (RG-59; 20 m-ohm, 21 pF, 118 nH per foot), and a low-capacitance cable I have used in the past (RG-63; 93-ohm impedance, 20 m-ohm, 10 pF, 86.5 nH per foot). I used 3 foot and 6 foot lengths (roughly 1m and 2m) in my trials, and distributed the impedance over ten stages/foot for better accuracy (100 stages/foot made essentially no change). I suspect most cables will fall around this range.

In the figures below I used four source (preamp-out) resistances: 100, 200, 500, and 1000 ohms. This spans the range I found plus a bit. I found a range from 0.2 to 0.01 ohms/ft interconnect resistance made no change in the results (<0.1 %). I plotted the frequency response from 10 Hz to 1 MHz, and calculated the response at 20 kHz relative to 10 Hz. There is essentially no significant loss at 20 kHz for any of these tests. Solid lines show 75-ohm cables, and dashed 93-ohm (low-C). Note the vertical scale is only 0.1 dB/division.

Figure1small..JPG

Figure 1: 3’ Interconnects​

Figure2..JPG

Figure 2: 6’ Interconnects​

As you can see, there is virtually no loss at 20 kHz for any trial (-0.003 dB worst-case). While there can (and probably are) special cases, to me this shows that, for relatively short runs of typical cable and normal preamp/amp designs, there is little likelihood of frequency response being an issue. This does not address shielding or the myriad second and higher order effects that may be present, of course. However, I thought folk might find this interesting.

HTH - Don
 

amirm

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Nicely done Don. Why don't I post some measurements I performed using AP of a generic cable vs Transparent Audio interconnections. First, at the standard 20 ohm output impedance of AP:



We see ruler flat response for both cables.

Now with AP output impedance of 600 ohms:



So the Transparent cable shows 0.1db drop off at 20 Khz. The generic is still essentially flat as your simulations showed.
 

muralman1

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Nicely done Don. Why don't I post some measurements I performed using AP of a generic cable vs Transparent Audio interconnections. First, at the standard 20 ohm output impedance of AP:



We see ruler flat response for both cables.

Now with AP output impedance of 600 ohms:



So the Transparent cable shows 0.1db drop off at 20 Khz. The generic is still essentially flat as your simulations showed.

Amir, this is not a surprise at all to me.
 

Phelonious Ponk

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So Transparent is not transparent. Close enough, though. Us middle-aged guys have a better chance of dating Scarlett Johannson than we have of hearing 0.1db off at 20 khz. Wouldn't it also follow that if components are designed for flat frequency response and within "normal" ranges of input resistance and output impedance, and "standard," well-shielded 75 ohm cables are used, there should be no synergy issues, other than headroom to efficiency, until you get to the transducers and the room? Or perhaps not. What are these "higher order effects" Don, and how can they audibly alter the signal?

Tim
 

microstrip

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Don,
Good work, but these simulations and measurements have been done hundreds of times and always shows the same - frequency response is not is not an acceptable explanation for the sound of cables.

Then we have two possibilities - either you say all cables sound the same and the issue is finished, or you believe in your ears and must be prepared for hearing some friendly jokes about our dating capabilities ;) .

Although I do not pretend to know or find an explanation for cable sound, I can help with two points. Usually cables from the same manufacturer show some systematic similarity in sound type (matching the sound type of an interconnect and a speaker cable should be a difficult task) and unhappily expensive cables manage to sound better than the inexpensive ones.
 

ack

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Thanks Amir - I've always contended that Transparent aren't really high bandwidth cables and now there is data to prove it. I believe it's their MIT-knock-off networks doing this. I had a pair of MusicWave speaker cables about 15 years ago - sold to me as "high bandwidth" - and couldn't stand them; last time I bought anything w/o doing any research.
 

mep

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If you believe there is some snake oil being sold in our audio world, you need to look no further than wires and cables to find the viper’s nest. How many audio cable companies actually have at least one EE on staff? How many audio cable companies actually possess test gear to measure their cables? My guess is damn few. To my knowledge, there isn’t a single audio cable company that manufacturers the wire that makes up their cables. Everybody buys wire from wire manufacturers made to their *specifications* and then dresses the wire up to look pretty so it can be sold for 1000% profit.

I doubt that very many golden ear audiophiles could pick out their personal world-beater cables from bottom-line Monster Cables in a blind-test (just to name one company). The bottom line is that if you imagine that your cables have made a big difference in the sound of your system, they have already proven their worth to you and no one should criticize you for being happy with your purchasing decision. At the end of the day we only have to please ourselves. Trying to convince others to hear what you hear is an exercise in futility.
 

microstrip

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Thanks Amir - I've always contended that Transparent aren't really high bandwidth cables and now there is data to prove it. I believe it's their MIT-knock-off networks doing this. I had a pair of MusicWave speaker cables about 15 years ago - sold to me as "high bandwidth" - and couldn't stand them; last time I bought anything w/o doing any research.

Ack,

Amir is showing a graph of the response of an interconnect, not a of a speaker cable as you have owned. I know that Transparent cables changed a lot during the last 15 years, but have owned several types during the last 20 years and never was told that they were "high bandwidth". On the contrary if you read their site you will find why they consider cable bandwidth should be limited.

See "Why Audio Cables Need Networks"

http://www.transparentcable.com/design/audio_cable_networks.php?catID=1&modCAT=1

Surely some people will disagree and/or will not like them.

BTW, one of the best sounds in my "top 10 list" was a Martin Logan system with Transparent cables.
 

microstrip

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(...) I doubt that very many golden ear audiophiles could pick out their personal world-beater cables from bottom-line Monster Cables in a blind-test (just to name one company). The bottom line is that if you imagine that your cables have made a big difference in the sound of your system, they have already proven their worth to you and no one should criticize you for being happy with your purchasing decision. At the end of the day we only have to please ourselves. Trying to convince others to hear what you hear is an exercise in futility.

Do you think the same about CD players and amplifiers?

I agree only with your last sentence, do you use the same epithet to class the exercise of those who try to convince others that they do not hear what they hear? :confused:
 

ack

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Ack,

Amir is showing a graph of the response of an interconnect, not a of a speaker cable as you have owned. I know that Transparent cables changed a lot during the last 15 years, but have owned several types during the last 20 years and never was told that they were "high bandwidth". On the contrary if you read their site you will find why they consider cable bandwidth should be limited.

See "Why Audio Cables Need Networks"

http://www.transparentcable.com/design/audio_cable_networks.php?catID=1&modCAT=1

Surely some people will disagree and/or will not like them.

BTW, one of the best sounds in my "top 10 list" was a Martin Logan system with Transparent cables.

First of all, IC vs speaker cable is same difference to me. Second, I've always found their claims nonsense... If you read their piece carefully, they say "effectively rolls off the ultra high frequency bandwidth of the cable" - their definition of ultra high frequency is apparently much different than mine and that of the data presented here.
 
Last edited:

mep

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Do you think the same about CD players and amplifiers?

No. CD players sound different and amplifiers damn sure sound different.


I agree only with your last sentence, do you use the same epithet to class the exercise of those who try to convince others that they do not hear what they hear? :confused:

The saying will work both ways: “Trying to convince others that they don’t hear what they hear is an exercise in futility.” I for one do believe that cables/interconnects have an influence on the sound. I want good quality wire that is well-shielded and terminated with high-quality connectors. What I don’t believe is that the high-priced spread can be justified in terms of the actual cost of manufacturing.

I knew Karen Sumner when she was running Transparent Audio out of her house in Maine. They started off using MIT cables and she just had some women at her house watching soap operas while they terminated cables and packaged them up for sale. That was back in the day when the RCA connectors they were using were made by Mogami and they weren’t all that great. Anyway, there were three principles that founded Transparent Audio. Karen, her husband Jack who was a school principal, and Carl Smith who was a lawyer. To say that Transparent Audio became a smashing success is an understatement.

I still have a pair of MIT speaker cables I bought from Karen and a pair of MIT-330 shotgun interconnects that were given to me by Carl Smith for building him a pair of transmission line subs. I believe their current business model is that they have no *employees* terminating cables for them now. They have independent contractors who are paid by the piece. They come to Transparent and pick up the wire and connectors, go home and assemble them, and bring them back and get paid for their piece work. This model will keep Transparent’s costs down because they are paying no benefits, no unemployment, and no taxes for their independent contractors.

I currently have a pair of bi-wire MIT S3 Shotgun speaker cables in my system that have magic network boxes with some amount of “poles of articulation.” I don’t know how articulated my poles are, but I’m happy with the cables. I love the fact that you can switch between spades or banana plugs in a few minutes.
 

c1ferrari

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Don and Amir,

Can you conduct an analysis of distortion? Would they possibly yield similar results and parallel conclusions? Rather curious, would a network analyzer be preferred over a spectrum analyzer for such an investigation? Thanks for sharing your work! By-the-bye, Amir, what AP are you running?
 

amirm

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Sure. I am not home right now but once I get back, I will run a distortion test. I also have Transparent speaker cables and can test those also.

BTW, how would I measure distortion? I need a reference and the reference is usually a wire!!! Maybe I can test different wires as I did.

A network analyzer will tell us what we know, that the cables do have different characteristics. But won't tell us what that means.
 

DonH50

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Just a few comments:

1. I realize this has all been done before; was not sure it had been done here. Feel free to ignore it; I thought perhaps some had not seen it before and so it might be interesting to them.

2. Amir, what length cable, and what source and load impedance were used for your curves? I am a little surprised at the roll-off, but OTOH rolling off the highs probably does make the sound less "bright". I have noticed over the years that a lot of people do not like a flat system, generally preferring a little more bass and a little less on the high end (at say 5 - 8 kHz and above).

3. I have no way to measure distortion of the cables now (new job, fewer toys for this kind of stuff). I have done so in the past and found essentially nothing. At audio frequencies (actually, well into the AM band and beyond) any nonlinearity in a cable is in the uV region (-120 dB from 1 V). Whatever distortion people are hearing, I strongly suspect it is not the cable itself.

4. Ditto cable noise. A 1 ohm resistor with 1 MHz bandwidth generates about 161 nVrms voltage noise, or 0.161 uVrms. Seems a pretty small level to be heard... The noise increase with the square root of resistance, so a 100 ohm cable would add 1.6 uVrms noise. Still pretty small...

5. I did not expect to prove or disprove anything, just sharing observations. My experience has been that audible and measurable differences (at the system level) are more likely with speaker cables than with interconnects, and even then primarily at extremes (e.g. badly mismatched cable/component combinations). I don't have speaker load models at the moment; maybe later, in another thread.

FWIWFM - Don
 

DonH50

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What can cause diffferences?

1. RFI/EMI -- poor shielding/grounding.

2. Loading of the preamp, and/or interaction with the power amp's input. I consider this relatively unlikely except in rare special circumstances or very high impedances.

3. Following up on (2), I have run across very wideband preamps in the past that would ring or even oscillate at very high (ultrasonic) frequencies with highly-capacitive cables. This robbed headroom and modulated lower-frequency signals, creating audible distortion.

Not sure what else, have to ponder on it a bit... - Don
 

Orb

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If you believe there is some snake oil being sold in our audio world, you need to look no further than wires and cables to find the viper’s nest. How many audio cable companies actually have at least one EE on staff? How many audio cable companies actually possess test gear to measure their cables? My guess is damn few. To my knowledge, there isn’t a single audio cable company that manufacturers the wire that makes up their cables. Everybody buys wire from wire manufacturers made to their *specifications* and then dresses the wire up to look pretty so it can be sold for 1000% profit.

I doubt that very many golden ear audiophiles could pick out their personal world-beater cables from bottom-line Monster Cables in a blind-test (just to name one company). The bottom line is that if you imagine that your cables have made a big difference in the sound of your system, they have already proven their worth to you and no one should criticize you for being happy with your purchasing decision. At the end of the day we only have to please ourselves. Trying to convince others to hear what you hear is an exercise in futility.
I think your right in most cases, but two come to mind straight away that do manufacturer their cables, Yter and Supra Cables (Jenving).
Sure a few others do as well but not many I agree.

Cheers
Orb
 

microstrip

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First of all, IC vs speaker cable is same difference to me. Second, I've always found their claims nonsense... If you read their piece carefully, they say "effectively rolls off the ultra high frequency bandwidth of the cable" - their definition of ultra high frequency is apparently much different than mine and that of the data presented here.

Sorry, but what is the nonsense of the sentence? Most good cables have reasonable transmission at 300 MHz and a network can roll it. Just one detail - perhaps a more careful writing would drop the "ultra", but I do not consider it of great importance.
 

fas42

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If there is one thing that should be got out of the way quick smart in terms of influencing sound it is interconnect cable. It is merely equivalent to the internal connection between stages of an integrated amplifier or playback system, and if you are going to fuss over that you may as well fuss over every single piece of wire internal to your components. Heavens above, if you want to really get serious about it, drill a hole in the casings such that the holes are adjacent when the components are stacked and hardwire in the shortest run through, with shielding around the connection space. Problem solved!!

Frank
 

ack

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Sorry, but what is the nonsense of the sentence? Most good cables have reasonable transmission at 300 MHz and a network can roll it. Just one detail - perhaps a more careful writing would drop the "ultra", but I do not consider it of great importance.

Perhaps it's just me, but I never thought audio nirvana would be achieved in part by using cables that roll off at the edge of human hearing, and sharply thereafter as Amir's data depicts... There are articles out there that show musical instrument overtones to 102.4kHz. Glad you like these cables.
 

microstrip

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Perhaps it's just me, but I never thought audio nirvana would be achieved in part by using cables that roll off at the edge of human hearing, and sharply thereafter as Amir's data depicts... There are articles out there that show musical instrument overtones to 102.4kHz. Glad you like these cables.

You should situate these cables in their time. They were Transparent entrance cables and at that time digital was not so perfect as today and most cheap/medium price CD players would benefit from this type of early roll-off.

I have measured some more recent, but not current model, Transparent interconnects and they roll-off at over 100 kHz. BTW, I like Transparent, but also many other brands - Cardas, Van den Hul, Shunyata, Nordost, Kimber, just to nominate a few I have tried. But IMHO each one is appropriate to a certain system - such thing as the best cable does not exist.
Soon I will measure some Transparent OPUS MM2 interconnects and I will post the results in WBF.
 

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