a/b interconnect cable comparison single ended

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Sean posts:

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

Sean I know the tape loop method will allow easy switching back and forth, but is it a true A/B comparison. 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? And are you not putting the two ics in series with one another when using the tape loop.

Please explain what you meant about using my method, of connecting two sets of cables connected to two different line inputs on a preamp, being parallelled and could effect the load impedance. My Arcam Alpha 9 CDP has two line out outputs. I have in the past installed two sets of ics to two sets of line inputs on my Sonic Frontiers Line one preamp and switch from one input to the other. When I switch from one input to the other, doesn't the input that is not connected to the CDP open and there for there is not any signal flow thru that pair of ics?
jim

"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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Thanks sean,
I was thinking more in terms of A/B comparisons of two different pair of ics, not just to listen to a particular cable for it's sonic character. I would agree the tape loop path would be a quick way to do that.

As for my comment on the two cables being in series, again I was thinking more in terms of an A/B comparison of two sets of ics. When I said in series I meant when the tape loop was engaged the signal path would be, source > ics from source to preamp input > second pair ics connect to tape loop in and out jacks > back to preamp signal path.
Jim

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