Hello and welcome to whatishifi blog.
Let me start the post with this: my experience up to now regarding speaker and interconnect cables can be found at this post. Also, my experience regarding coaxial and optical connection can be found at this older post.
I frequently hear the opinion that XLR connection sounds better than RCA. I also know that XLRs have a higher (louder) output, something that is not always taken into consideration - at an audio comparison test, if everything else is equal, louder is considered as better by the human ear. I always wanted to make a reliable test, but never had the opportunity. But the arrival of a new system - among other things - lead to a new blind test and a new interesting post at this blog.
First, let's see some theory. RCA cables (or unbalanced interconnects) have two wires, a positive and a negative. The negative wire is also the shielding. XLRs (or balanced interconnects) have three wires: two signal wires and a shielding. Now, what happens here is that both the two signal wires carry the music signal but the one wire carries it at 180 degrees (out of phase) in regards to the other. The first benefit is that you have a dedicated ground / shield wire. The second benefit is what is called "common mode rejection": the receiver will understand as a music signal anything that is in opposite phase in the two signal wires and will reject any cable interference (like hum for example) that will be at same phase at both signal wires. A nice video regarding XLR and RCA interconnects is this one.
So, any equipment that wants to be called Hi End and respects itself has also XLR ins & outs. However, there is a catch here: you can connect an RCA cable at an XLR input and vice versa with a simple adapter, but you loose the theoretical benefits of the balanced connection. Sometimes, this simple adapter is build in at a device, meaning that although the device has XLR balanced connectors, it is not a truly balanced design. If you want to learn more about this, here is a nice video.
Another catch is the volume control pot at the pre amps. A true balanced design requires a double volume control (one part for the normal signal and one part for the inverted signal). But some "smart" manufacturers, although they have included the extra circuits required for a true balanced design at the pre amp, what they do is before the volume control pot they make the signal unbalanced, they pass it from a normal pot and then they make the signal balanced again.
XLRs are also the standard connectors for professional audio applications. They lock securely into place, they are thick, impressive and good looking. To be honest, when I was connecting the system we used for the testing with some fancy XLR cables I almost fell in depression because my main system has no XLR option. Also, rumors say that XLRs will definitely sound superior, something that further increased my curiosity for a comparison test.
First attempt to understand if XLR sounds better than RCA was the day I brought the PS Audio PCA 2 pre amp at Pano's home for some comparison tests. His Parasound A-21 power amp has XLR inputs so we connected the PCA 2 to the A-21 both ways, trying to understand if we could hear any benefits. Well we didn't - but since the procedure required to stop the music, turn off the A-21, change the input selector switch at the back of A-21, turn it on, adjust the volume and listen again, we thought that maybe the difference was so small that only an instant A/B comparison would help us appreciate it.
So, we prepared for a proper and revealing blind A/B comparison test. The Accuphase DP-500 CDp was connected with Kimber Orchid Illuminations XLR cables at the input 1 and with our DIY (good but not exotic) RCA cables at input 2 of the PS Audio PCA 2 pre amp. The pre amp was connected through PS Audio xStream Audio Statement XLR cables to the mighty PS Audio Classic 250 power amp. The speakers we used were the EgglestonWorks Isabel (with the legendary Dynaudio Esotar tweeter), standing at their own Eggleston factory stands. The speakers were connected to the power amp through Synergistic Research Resolution Reference speaker cables with active shielding - not that it matters, but I guess it ads some status.
A comment for using Kimber XLR cables designed for AES / EBU digital connection as analogue interconnects: yes, you can do that without any problem - it is the opposite that you can't do, meaning you can not use a cable designed for analogue connection at a digital connection. Explaining why goes out of the purpose of this post, so let me cover this subject quick and not in depth: the special characteristics required at a digital cable do not harm analogue sound. However, the lack of these special characteristics do harm digital transfer. Just out of curiosity I tested the Kimbers as an analogue cable and they behave just fine. At the end of the post you may read about this test procedure.
The CD albums we used were a common CD album of Dire Straits Money For Nothing, a sample disk from Mapleshade and a sample disk from Cisco Music - the last one fits this particular setup (that is a bit picky regarding the music / recording) extremely well.
We checked that the volume between input 1 and 2 was the same and we proceed with our blind test; one of us was changing inputs at the pre amp, and the other one should pick up what he considers sounds best without knowing which type of connection is listening to.
The test turned out to be a very easy one, RCA connection was a clear winner. Both of us preferred it 3 out of 3 times at our blind testing. The reason was that the low end was deeper and better controlled with RCA connection.
We found the result amusing, but also awkward. Our next step was to change the connection of the pre amp to the power amp to RCA. As soon we did this, the system didn't care regarding if the CDp was connected to the pre amp balanced or unbalanced; both connections were sounding the same. Also, the RCA connection from the pre to the power amp did not degrade overall the sound quality.
We found this result even more awkward. We tried to give a reasonable explanation but we couldn't come with one. Anyway, we replaced the Classic 250 with a PS Audio HCA-2 power amp (the HCA-2 was connected to the PS Audio Power Plant Premier AC regenerator since this is one of a few cases where the Premier regenerator has something to offer sound wise) and we started again our blind test. Oh, let me say that the Classic 250 has it's own factory build in, factory tailor made and fine tuned regenerator for the input state.
With the HCA-2 connected to the pre amp with XLR cables, both the XLR and the RCA connection from the CDp to the pre amp sounded the same. We connected the HCA-2 to the pre amp by RCA; again, both the XLR and the RCA connection from the CDp to the pre amp sounded the same. Also, connecting the HCA-2 to the pre amp with RCA did not seem to degrade the sound quality.
So, our conclusion was that XLRs do not necessarily sound better from RCAs. We even had this one awkward case with the Classic 250 were XLRs sounded worse, but I guess this is an exception. Now, for bigger lengths of interconnects maybe XLR cables will start sounding better than RCA - or to put it more accurate, RCA cables maybe will deteriorate the sound quality if their length becomes too big - and this maybe also depends from the connected equipment, not just the cables itself. For home use, don't feel bad if your equipment do not offer XLR connection; it is not that you are missing something due to that. Balanced connection is not a panacea of better sound or a sound quality inferiority. Of course XLR is welcomed, but I wouldn't make any decisions regarding choosing equipment based on that.
Last but not least, producing a true balanced component is much more expensive than an unbalanced one, since it XLRs virtually need double the circuits. So apart from a philosophical point of view, we get a practical scale of economics kind of question: for a certain budget, should you spend your money buying double XLR circuits, or should you spend them buying a better pair of speakers for example? My personal opinion is that you should choose the second scenario.
Happy listening as always, balanced or unbalanced.
Christos
Here is the test procedure regarding verifying that a XLR cable designed for digital connection behaves normally as an analogue cable. With the Classic 250 power amp connected with RCA to the pre amp (so both the XLR and the RCA connections from the CDp to the pre amp sound the same), I connected the CDp with the PS Audio XLR cables and compared them with Van Den Hul RCA cables - they sounded the same. Then, I replaced the PS Audio XLR with the Kimber digital cables and compared them again to the Van Den Hul; they sounded the same. That leads us to the conclusion that both XLR cables behave exactly the same.
Let me start the post with this: my experience up to now regarding speaker and interconnect cables can be found at this post. Also, my experience regarding coaxial and optical connection can be found at this older post.
I frequently hear the opinion that XLR connection sounds better than RCA. I also know that XLRs have a higher (louder) output, something that is not always taken into consideration - at an audio comparison test, if everything else is equal, louder is considered as better by the human ear. I always wanted to make a reliable test, but never had the opportunity. But the arrival of a new system - among other things - lead to a new blind test and a new interesting post at this blog.
First, let's see some theory. RCA cables (or unbalanced interconnects) have two wires, a positive and a negative. The negative wire is also the shielding. XLRs (or balanced interconnects) have three wires: two signal wires and a shielding. Now, what happens here is that both the two signal wires carry the music signal but the one wire carries it at 180 degrees (out of phase) in regards to the other. The first benefit is that you have a dedicated ground / shield wire. The second benefit is what is called "common mode rejection": the receiver will understand as a music signal anything that is in opposite phase in the two signal wires and will reject any cable interference (like hum for example) that will be at same phase at both signal wires. A nice video regarding XLR and RCA interconnects is this one.
So, any equipment that wants to be called Hi End and respects itself has also XLR ins & outs. However, there is a catch here: you can connect an RCA cable at an XLR input and vice versa with a simple adapter, but you loose the theoretical benefits of the balanced connection. Sometimes, this simple adapter is build in at a device, meaning that although the device has XLR balanced connectors, it is not a truly balanced design. If you want to learn more about this, here is a nice video.
Another catch is the volume control pot at the pre amps. A true balanced design requires a double volume control (one part for the normal signal and one part for the inverted signal). But some "smart" manufacturers, although they have included the extra circuits required for a true balanced design at the pre amp, what they do is before the volume control pot they make the signal unbalanced, they pass it from a normal pot and then they make the signal balanced again.
XLRs are also the standard connectors for professional audio applications. They lock securely into place, they are thick, impressive and good looking. To be honest, when I was connecting the system we used for the testing with some fancy XLR cables I almost fell in depression because my main system has no XLR option. Also, rumors say that XLRs will definitely sound superior, something that further increased my curiosity for a comparison test.
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| The PS Audio PCA 2 pre amp offers a plethora of connections, both balanced and unbalanced. |
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| Our system used for this test, from top to bottom: PS Audio HCA-2 power amp, PS Audio PCA 2 pre amp, Accuphase DP-500 CD player, PS Audio Power Plant Premier AC regenerator, PS Audio Classic 250 power amp. At the right the EgglestonWorks Isabel speaker, standing on its own stand. |
A comment for using Kimber XLR cables designed for AES / EBU digital connection as analogue interconnects: yes, you can do that without any problem - it is the opposite that you can't do, meaning you can not use a cable designed for analogue connection at a digital connection. Explaining why goes out of the purpose of this post, so let me cover this subject quick and not in depth: the special characteristics required at a digital cable do not harm analogue sound. However, the lack of these special characteristics do harm digital transfer. Just out of curiosity I tested the Kimbers as an analogue cable and they behave just fine. At the end of the post you may read about this test procedure.
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| Some of our cables. |
We checked that the volume between input 1 and 2 was the same and we proceed with our blind test; one of us was changing inputs at the pre amp, and the other one should pick up what he considers sounds best without knowing which type of connection is listening to.
The test turned out to be a very easy one, RCA connection was a clear winner. Both of us preferred it 3 out of 3 times at our blind testing. The reason was that the low end was deeper and better controlled with RCA connection.
We found the result amusing, but also awkward. Our next step was to change the connection of the pre amp to the power amp to RCA. As soon we did this, the system didn't care regarding if the CDp was connected to the pre amp balanced or unbalanced; both connections were sounding the same. Also, the RCA connection from the pre to the power amp did not degrade overall the sound quality.
We found this result even more awkward. We tried to give a reasonable explanation but we couldn't come with one. Anyway, we replaced the Classic 250 with a PS Audio HCA-2 power amp (the HCA-2 was connected to the PS Audio Power Plant Premier AC regenerator since this is one of a few cases where the Premier regenerator has something to offer sound wise) and we started again our blind test. Oh, let me say that the Classic 250 has it's own factory build in, factory tailor made and fine tuned regenerator for the input state.
With the HCA-2 connected to the pre amp with XLR cables, both the XLR and the RCA connection from the CDp to the pre amp sounded the same. We connected the HCA-2 to the pre amp by RCA; again, both the XLR and the RCA connection from the CDp to the pre amp sounded the same. Also, connecting the HCA-2 to the pre amp with RCA did not seem to degrade the sound quality.
So, our conclusion was that XLRs do not necessarily sound better from RCAs. We even had this one awkward case with the Classic 250 were XLRs sounded worse, but I guess this is an exception. Now, for bigger lengths of interconnects maybe XLR cables will start sounding better than RCA - or to put it more accurate, RCA cables maybe will deteriorate the sound quality if their length becomes too big - and this maybe also depends from the connected equipment, not just the cables itself. For home use, don't feel bad if your equipment do not offer XLR connection; it is not that you are missing something due to that. Balanced connection is not a panacea of better sound or a sound quality inferiority. Of course XLR is welcomed, but I wouldn't make any decisions regarding choosing equipment based on that.
Last but not least, producing a true balanced component is much more expensive than an unbalanced one, since it XLRs virtually need double the circuits. So apart from a philosophical point of view, we get a practical scale of economics kind of question: for a certain budget, should you spend your money buying double XLR circuits, or should you spend them buying a better pair of speakers for example? My personal opinion is that you should choose the second scenario.
Happy listening as always, balanced or unbalanced.
Christos
Here is the test procedure regarding verifying that a XLR cable designed for digital connection behaves normally as an analogue cable. With the Classic 250 power amp connected with RCA to the pre amp (so both the XLR and the RCA connections from the CDp to the pre amp sound the same), I connected the CDp with the PS Audio XLR cables and compared them with Van Den Hul RCA cables - they sounded the same. Then, I replaced the PS Audio XLR with the Kimber digital cables and compared them again to the Van Den Hul; they sounded the same. That leads us to the conclusion that both XLR cables behave exactly the same.
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