One reason that "opinions are somewhat contradictory and confusing" is that which interconnection scheme will be most optimal is highly dependent on the specific components and cable that are involved, and in particular on design dependent variables that are generally unspecified and unpredictable.
For example, if the quality of the DAC in a player can be presumed to be inferior to the quality of the DAC in an amp, it could conceivably still be preferable in some cases to use the DAC in the player instead of the one in the amp if the digital interface in one or both components has particularly high levels of jitter (short term random or pseudo random timing fluctuations), or if the impedance match between the digital interfaces of both components and the cable happens to be less than good, or if the design of the two components is more susceptible than average to effects on their digital interfaces that may result from ground loop issues. Etc. etc.
I’m not sure from your post if the XLR inputs and outputs you referred to are analog or digital. A digital XLR interface would most commonly be referred to as an AES/EBU interface. Also, assuming the coaxial inputs and outputs you referred to are digital, they would most commonly be referred to as coaxial digital or coaxial S/PDIF. A coaxial connection via RCA connectors could also refer to an analog interface.
Also, for AES/EBU or coaxial S/PDIF interfaces, more often than not the lengths you specified will not be optimal. Somewhat counter-intuitively a length of 5 or 6 feet will more often than not be preferable to those lengths, or if a very short length is practicable (e.g., around 8 inches or less), that would probably be even more preferable. Intermediate lengths such as 1 meter, or even 0.4 meters, are often (although not always) less preferable. See this paper for further explanation. In the case of analog interfaces though, and I suspect also in the case of Toslink interfaces (although I’m not totally certain about Toslink), the shorter the better (assuming the goal is to minimize the sonic effects of the cable).
Regarding analog XLR interfaces vs. analog RCA interfaces, which is preferable depends on the designs of the particular equipment. In theory, assuming equal quality of implementation, an XLR analog interface is preferable. However XLR interfaces are in many cases are not as well implemented as RCA interfaces, especially at moderate or lower price points.
But to address your question specifically: My perception, based on many anecdotal reports I have seen as well as my own experience, would be that more often than not the greatest likelihood of optimal results would result from the following, in descending order of preference:
If the player is described as providing analog XLR outputs and as having a balanced internal signal path from its DAC circuit to those outputs, and if that internal DAC is expected to be of reasonably good quality:
Analog XLR > Analog RCA > AES/EBU > coaxial S/PDIF > Toslink
If the player is not so described:
AES/EBU > coaxial S/PDIF > analog RCA > analog XLR > Toslink.
The ranking of Toslink may be improvable by using a relatively expensive (but presumably more fragile) glass cable, rather than a plastic one, or by using this relatively inexpense (and non-fragile) cable from Analysis Plus (which I have used with fine results in a relatively non-critical application).
FWIW, also, I have had fine results with this relatively inexpensive Mogami AES/EBU cable.
Other opinions will certainly differ in many cases.
Hope that helps. Regards,
-- Al
For example, if the quality of the DAC in a player can be presumed to be inferior to the quality of the DAC in an amp, it could conceivably still be preferable in some cases to use the DAC in the player instead of the one in the amp if the digital interface in one or both components has particularly high levels of jitter (short term random or pseudo random timing fluctuations), or if the impedance match between the digital interfaces of both components and the cable happens to be less than good, or if the design of the two components is more susceptible than average to effects on their digital interfaces that may result from ground loop issues. Etc. etc.
I’m not sure from your post if the XLR inputs and outputs you referred to are analog or digital. A digital XLR interface would most commonly be referred to as an AES/EBU interface. Also, assuming the coaxial inputs and outputs you referred to are digital, they would most commonly be referred to as coaxial digital or coaxial S/PDIF. A coaxial connection via RCA connectors could also refer to an analog interface.
Also, for AES/EBU or coaxial S/PDIF interfaces, more often than not the lengths you specified will not be optimal. Somewhat counter-intuitively a length of 5 or 6 feet will more often than not be preferable to those lengths, or if a very short length is practicable (e.g., around 8 inches or less), that would probably be even more preferable. Intermediate lengths such as 1 meter, or even 0.4 meters, are often (although not always) less preferable. See this paper for further explanation. In the case of analog interfaces though, and I suspect also in the case of Toslink interfaces (although I’m not totally certain about Toslink), the shorter the better (assuming the goal is to minimize the sonic effects of the cable).
Regarding analog XLR interfaces vs. analog RCA interfaces, which is preferable depends on the designs of the particular equipment. In theory, assuming equal quality of implementation, an XLR analog interface is preferable. However XLR interfaces are in many cases are not as well implemented as RCA interfaces, especially at moderate or lower price points.
But to address your question specifically: My perception, based on many anecdotal reports I have seen as well as my own experience, would be that more often than not the greatest likelihood of optimal results would result from the following, in descending order of preference:
If the player is described as providing analog XLR outputs and as having a balanced internal signal path from its DAC circuit to those outputs, and if that internal DAC is expected to be of reasonably good quality:
Analog XLR > Analog RCA > AES/EBU > coaxial S/PDIF > Toslink
If the player is not so described:
AES/EBU > coaxial S/PDIF > analog RCA > analog XLR > Toslink.
The ranking of Toslink may be improvable by using a relatively expensive (but presumably more fragile) glass cable, rather than a plastic one, or by using this relatively inexpense (and non-fragile) cable from Analysis Plus (which I have used with fine results in a relatively non-critical application).
FWIW, also, I have had fine results with this relatively inexpensive Mogami AES/EBU cable.
Other opinions will certainly differ in many cases.
Hope that helps. Regards,
-- Al