A-B testing of cables

I'd expect that you'll be receiving a variety of responses, including assertions that your system and/or your ears and those of the other listeners aren't "resolving enough," the recordings weren't good enough, the y-adapters and/or the doubled cables and/or loads that were applied to the CD player resulted in a loss of resolution (although based on the impedances that are involved **in this particular case** I doubt that was a problem), etc, etc.

IMO what you've mainly determined is that your particular hardware is not particularly sensitive to the differences between the two particular cables, in the lengths that you require. And that does not necessarily have anything to do with the musical resolution of the system.

Also, I think you'll find this thread to be of interest.

I assume, btw, that the test with the turntable was done by changing cables rather than with a y-adapter, as one of the two phono inputs on your preamp is for low output cartridges and the other is for high output cartridges.

Regards,
-- Al

Steve (Williewonka), re the blog post you referenced, keep in mind (as I'm sure you realize) that for current to flow a complete circuit has to be present, from source to destination and back to source.

When the output of one component provides a signal to the input of another component, there indeed has to be a path for the corresponding current to return to the source of the signal. And the quality of that return path will matter just as much as the quality of the path for the "signal." In fact, it will often matter more, as explained in the next paragraph.

Depending on the internal grounding configuration of the two components, even very small amounts of resistance in the return conductor may contribute significantly to ground loop issues, which can in turn result in issues involving high frequency noise as well as low frequency hum. While the resistance of the signal conductor in a line-level interconnect that is conducting an analog audio signal will only matter if that resistance is a significant fraction of the impedances of the connected components, especially the input impedance of the destination component. And for line-level analog interconnections, that resistance will be a totally miniscule fraction of that input impedance in nearly all home audio systems.

Regards,
-- Al

Hi Steve,

Agreed for the most part, and the experience described in your second from last paragraph makes a lot of sense. However, a current will indeed flow in the return conductor of an unbalanced line-level interconnect, that is equal to the current in the signal conductor. Or, at least, the two currents SHOULD be equal. Any slight differences that may exist between them would mean that some fraction of the return current is finding an alternate path, such as the return conductors of other cables that may be connected between the same components, or through the AC safety ground connections of the two components (which would constitute a ground loop issue, to some degree that may or may not have audible consequences).

But if the resistance and impedance of that return conductor is 0 ohms at all relevant frequencies (to a very close approximation), then the voltage drop from one end of that conductor to the other which results from the current flowing in it will be, per Ohm's Law, 0 volts (to a very close approximation). Which in turn will mean that the return conductor and the points in each component to which it is connected will all be at 0 volts, relative to the circuit grounds of both components. (Keep in mind that any voltage number, including 0, is only meaningful if a reference point is defined, at least implicitly. In this case the reference point(s) would be the circuit grounds of the two components).

In any event, thanks for sharing your experiences, which I know are particularly extensive in these kinds of matters.

Best regards,
-- Al

FWIW, I agree in part with the preceding posts by Doug and ZD, and disagree in part.

I think that the criterion of immediate efficaciousness, which Doug has stated a number of times in the past as well as above, has a lot to be said for it. Especially in the context of cables, as well as tweaks of various kinds. Although at the same time I recognize that there can be subtle differences that may take a relatively long time to initially perceive, but once initially perceived can then be identified fairly readily in subsequent listening.

I agree with ZD that there are problems with a comparison that involves only one channel of information. In addition to the issues he cited, there is the fact that while differences may be noted in many cases in such a comparison, one's ability to reach a meaningful conclusion as to which of the items being compared is "better," or at least subjectively preferable, will be compromised by the missing information. And also by the altered placement of the speakers in the proposed test.

Regarding splitters, from a technical standpoint my expectation is that in the majority of cases the negative experiences people often report with them are not caused by the splitters per se, but rather by one or more of the following:

1)The fact that the component supplying the signal is driving two load impedances, rather than one. The combined impedance of the two loads will always be lower (more challenging) than either of the two individual impedances, and will usually be MUCH lower. (To calculate that, multiply the two impedances together, and divide that product by the sum of the two impedances. To assure that the combined impedance won't be too low to be suitable, that result should be at least 10 times greater than the highest output impedance the component supplying the signal has ***at any frequency***).

2)The fact that the component supplying the signal is driving two cables, especially in regard to their capacitances. (The combined capacitance of the cables equals the sum of their individual capacitances). The combined capacitance of BOTH cables will affect the signals seen by BOTH components that are being driven, as a result of the interaction between that total capacitance and the output impedance of the component supplying the signal. In other words, to cite a common application of a splitter, if one is used to split the output of a preamp so that it is routed to both a powered sub and the main power amp, the capacitance of the cable to the sub can affect the high frequency content of the signal seen by the main power amp just as much as the capacitance of the cable which connects to the main power amp. Or even more, if the cable to the sub is longer than the other cable and/or has higher capacitance per unit length.

3)The possibility that sonics may be affected by low frequency, high frequency, or even ultrasonic noise that may be introduced as a result of ground loop effects occurring between the three interconnected components, that might not occur if only two of them were connected.

Regards,
-- Al