a/b interconnect cable comparison single ended

I do not understand how CableA-coupler-CableB is different than CableB-coupler-CableA.

The coolest way to do this is to use a line stage's tape monitor loop. You have the added RCA connectors on the line stage and the monitor switch itself, but these will be miniscule vs. the cable differences. And whatever detriments are caused here will be reflected by either cable.

Use CableA from source to line stage or line stage to amp and CableB from tape-outs to tape-ins. Toggle the tape monitor switch to engage/disengage CableB into the system and document the sonic changes caused by CableB when it is engaged. Repeat the test with the cable roles reversed. Whichever cable in the tape monitor loop causes the greater sonic changes between the 2 switch positions is the more "colored" cable.

On some older preamps, I believe the ARC SP11 and SP15, that had two tape loops, you could have an independent CableC as the IC used for the signal and engage CableA and CableB through the 2 tape monitor loops back and forth and then neither of them engaged.

John

John's idea of using the tape look to simply route signal through the cable is a good one, but there is one catch. That is, if you've not used the tape loops to any great extent, just switching them into the circuit will change the sonics regardless of the cables under test. This obviously has to do with "break in" and many will think that it is kinda crazy, but it is true. If in doubt, plug your CD player into a different input that you don't normally use ( NOT a phono input ) and see if you can hear a difference. We've done this using even mass produced receivers and the differences between various inputs was quite evident, even to the "non-audiophiles" that first noticed the differences in their system. Sean
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Thanks Sean and John,going to try that,cheers,Bob

Using rapid A/B comparisons I get some info, but not a complete data set.

With the theory that difference is not always better (or worse) I find I obtain more useful info by putting a given cable into the system and living with it for a while (days). Then take it out and put in the comparator and listen over a couple of days. I keep doing this until the one I want to live with emerges. If you feel a need to do this blind get a buddy or a kindly spouse to help. (Just don't peek!)

Sometimes a difference is initially disconcerting; sometimes the unfamilar is initally attractive. Long term satisfaction is what you really want.

On the other hand, to the extent you have a 'gold standard' as a comparitor, rapid testing can help find DUTs that are simliar in sound. Otherwise your comparisons lack a control. John's method (using cable 'c') does account for this. I also agree with Sean... any change you introduce, other than the variable you want to test, may confound your results.

So I keep it simple. Out with one, in with the other. Reverse, repeat. Works well for me.

Jea48: Using the tape loop allows one to use their existing set-up and simply switch the interconnects in and out of the system instantaneously. No need to remove, replace, reconnect, etc... All of this at a flip of a switch WITHOUT altering the load impedances by running cabling in parallel to two different input jacks. Sean
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"I know the tape loop method will allow easy switching back and forth, but is it a true A/B comparison?"

This is a method to see how "coloured" a cable is. It may not be representative of how the cable actually works in a different part of the circuit with different mating impedances.

"Is the signal path and switching contacts of the tape loop cicuit the same as the line inputs signal path and switching contacts of the preamp?"

This would depend on if the output jacks on the source were wired in parallel or if they were individually selectable. If they are in parallel, it would not be the same. If they are selectable, it would be almost the same. The difference would be that you would have to select outputs on the source and the inputs on the preamp. This would mean introducing two switches and their associated parts / signal path into the circuit rather than just one. More variables with more potential for outside influences.

On top of that, signal goes wherever it can, even if the circuit is open and there isn't a complete path for it to take. This is especially true of RF based signals, such as the digital output on a transport that one might use to feed a DAC. I know that this is contrary to what many people have been taught, but there's nothing that i can do about that. Since the cables themselves present a nominal impedance, signal will flow and they will effectively become part of the "load" that the device sees. This is true even if you and i see it as an "open circuit".

As such, using a device with parallel outputs and choosing between the cables at the preamp still places the nominal impedance of the unused interconnects in parallel with the signal path of the interconnects being used. Nothing short of switching them out of the circuit at the source or physically removing them would solve this potential variable.

"And are you not putting the two ics in series with one another when using the tape loop".

My take on this was that the system remained as it was and one was simply inserting cables for testing into the tape loop. This would allow one to maintain the sonics that they were used to and at the same time, allow them to switch the interconnect in and out as desired via the tape loop. If one noticed a large difference, the cable itself would probably be introducing its' own sonic influence. As previously mentioned though, there would also be additional impedance related alterations to the signal path due to the tape monitor circuitry and additional switching, etc...

As to your specific installation, i'm not directly familiar with either piece of gear i.e. the Arcam or the SF preamp. How each piece works in terms of selectable inputs and outputs and loading characteristics is a mystery to me. Sean
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That's what i thought you meant Jim, but thanks for clarifying it. That would put the cables in series, but as we've discussed, it would be far faster and more convenient to do this than to have to manually connect / disconnect as needed when trying to make this type of comparison. Sean
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Thanks Sean for your comments. They reflected exactly the points I was making here.

The reason I suggested the tape loop methodology was because of Mrtennis' statement, "use the results to help determine which of the two cables alters the sound more than the other." The key word was "alters". I think of this as an objective, i.e., quantitative test. It determines "coloration" and not which cable is to be preferred over another at any link.

Adding another cable to the chain shows up the design of only that one cable. Replacing a cable in the chain is much more tricky as both cables' designs come into play. Here it is not so easy to know which one is more "neutral". They both may be severely colored but in different ways. But one might just "lock in" with the system because this cable is complimenting non-linearities elsewhere in the system.

Because the tape outputs reside somewhat in the middle of the line stage's internal circuit, after the input selector but before the level adjustment, the added cable here would simulate neither the adding of a cable in series from the source NOR in series with the IC to the power amp. But this would quickly show up any cable non-linearities. I can not think of a better way to sonically determine this.

When we insert something in series, we know right away what has been altered. We have added more than a second cable here (connections and switches) but if we repeat this with multiple cable brands/models, we can ultimately determine the differences between each and ignore other alterations that we observed to be common to all. And they could be very insignificant to the cable differences anyway.

Inserting a cable like the Cardas Golden Cross would immediately show how colored this cable truly is. It would score very poorly in a quantitative test. The added connections and tape montior switch here would be moot vs. the changes brought on by this added cable. But such a cable could easily bring on much greater enjoyment if it replaced another in the system....and thus trigger a highly subjective "qualitative" result. A much more linear cable would bring the detriments of the extra connections and monitor switch more to the forefront.

For final cable selection, rather than try to quantify how each cable directly alters the signal, I would listen to one cable at a time in a given link rather than to use the tape-loop approach. This is because I am evaluating one cable to another rather than one cable to "perfection". Each methodology provides a different set of results, quantitative and qualitative, that are valuable to the final choice.

As my system's resolution has improved, I have found that no matter where an IC or PC is used in the system, that cable's effect on the resultant sound is fairly consistent. Only the magnitude of the change is the significant difference. At this point in time, after hearing Purist Dominus affect the system consistently no matter where it was used, and the same for the Kubala-Sosna Emotion, I would deduce that a cable in the tape loop would likely affect the system in a similar manner if used anywhere else.

John

my preamp does not have a tape monitor function. other than my original suggestion or use of the y-connector, is there an idea other than using some kind of passive junction "box"
to compare cable ?

my original question, "which of two cables is more colored" would require a signal to pass through both of them. having two pairs of cable connected to different inputs does not accomplish that.

suppose cable a is somewhat subtractive and cable b is somewhat additive. i would like to find out which of the two is "distorting" the signal more, a or b ?

regardless of the question , "which one does one prefer", is the question, "which one is more accurate", recognizing that both cables are not accurate or perfect. by the way, david salz of wireworld suggested the method i suggested above.

Mrtennis how could you ever 'know' which is more 'accurate' unless you could control (know) the input signal. And, as I am sure you would agree, more accurate on square waves (or other test signal) may not be more accurate with a musical signal. So how can we ever do better than find that which we prefer? Perhaps with a standard cable, we could find another cable 'most like' our standard. Even in this case all we could say is that we could identify a cable close to our standard within the constraints of a given system.

There is only an absolute within the relative. Using the metric of what live music sounds like we seek the best recreation of this event. 'Accuracy of the whole' may well be more than a sum of 'accuracy of the parts'.

Or perhaps I am inaccurate!

cjs

I discussed hooking cabling up to a distortion analyzer quite a while back. Some cables are far higher in distortion than others. John Curl has also discussed this over at AA.

With that in mind, this type of test still doesn't simulate the way that a cable acts as an impedance transformer between pieces of gear. Since no two pieces of gear have the same input / output impedances, the loading characteristics, distortion and sound WILL change somewhat from system to system / component to component.

As far as the approach that David Salz recommended, it really can't tell you too much of anything. One could easily see the electrical differences between the two cables and the variances in signal flow when hooked up in series using a network analyzer. However, attributing what sonics go with what cable, regardless of where Cable A is in relation to Cable B or vice-versa, would be nothing more than a crapshoot. That's because the source sees the combined electrical characteristics of the two cables and load component on the whole. Thevenin's theory teaches that the sum of impedances can be summed into one impedance. Then again, i've never been a huge fan of Thevenin's theory. Lumped and distributed impedances can and do very different things electrically, even though they might sum into equal values if looking at the circuit on the whole. Sean
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mr smith, you are correct. one cannot know which of 2 cables are less accurate0.

however, anecdotally, you might have confidence based upon listening, which of the two cables seems to alter the signal to a greater degree, at the listener position, using spectral analysis. i realize this is not a definitive test, and, as you indicate one cable may be preferred, but as a first step, it may provide some useful information.

Mr. T: you note you'd like to find

'which of the two cables seems to alter the signal to a greater degree'

How do you know what the signal is suppose to be?

If we take our time and listen carefully for the sound of live music in our audio rooms (creating the illusion of sound/space) we will select out increasingly 'accurate' components where accuracy means accuracy in recreation of the encoded musical moment.

Perhaps it would be useful to make a recording of some music made in my audio space. I suspect that advances in digital technology make it a realistic proposition that an serious amateur could make a high quality encoded musical moment in their living space which could in turn be used as a high quality 'test signal' for evaluation of their audio system. It's late, I'm rambling on but I think you can get my drift. Or am I out of my mind? (one audiophile to another!)
cjs

hi cjsmith, your point is well taken.

suppose you had a high quality spectral analyzer.

suppose you had a cd which contained white or pink noise.

if you follow my paradigm, one of the cables might exhibit greater frequency response deviations, when the spectral analyzer is set up at the listening position.

yes, the room is part of the equation, but the room is a constant.

Mr. Tennis
I'd say that your approach in having better comparison means instead of the classic pause (shut down) disconnect, reconnect, seat, play again is good. It can give you a better glimpse of each cable characteristics faster. That doesn't mean you are not going to listen to each cable for longer periods to really have a more thorough evaluation.

Point to remember when you try anything at home: you'll select what appeals best to your ears, not necessarily what is the "truest cable".
In other words if it's closer to the ideal cable is one matter, that the user likes, enjoys, foot taps what is heard is another; in my book the latter overwhelms the former, because I look for music enjoyment.

On the inputs regarding tape loop for the evaluation, I agree with Sean that there are differences indeed. As a matter of fact I choose the input connector based on what I hear sounds better not necessarily because the manufacturer marked a determined input “CD” for example.

You can assess the difference the input makes on the result swaping cable/ input and re-evaluate. Another approach is to use one single cable and evaluate it using input “A” then input “B” and hear if the existing difference is that relevant to your evaluation results.

I think we have to simplify this hobby a little and enjoy the music more.... just my 2 cents guys

Luis

Luis, I find that my enjoyment of this hobby stems from the fact that I can listen to music or think about physics or do some soldering or worry aobut chemistry (record cleaning) or the biology of hearing or just listen to music. I mean, it's all fun or it's not a hobby!

Mr. T - I agree. Wish there was a simple 'cable distortion test' as you describe. However the test might not always correlate with which cables we find musical - which would give us some additional questions to ask. I don't have an occilliscope (yet) but I wonder if you put standard signals (e.g. square waves) thru various cables are they all identical?

cjs

Altering the source and load impedances can vary the response that a cable would demonstrate under these test conditions. This is the same thing that happens when you change components i.e. the load and / or the source impedance is altered. As such, one can simulate various circuit combo's and see how each cable responds accordingly. Why there aren't any reviewers / manufacturers doing anything like this, i don't know. Sean
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