I remembered this thing when we conducted the blind test last week. The RCA Splitter shouldn’t be used when examining the character of two cables. Read more to understand the scenario.
Some people used to use splitter like picture above to compare two cables. The schema should be like this:
Usually, we have one line out only from our source (CD/DVD Player or sound card). So, we will use a splitter like picture on the top of this page. This splitter will split the source signal into two cables. Most amplifier should have multiple input selector (some offer more than two). So, we connect all (two) cables to the input #1 and input #2 on the amplifier. For blind test or compare these two cable, we usually change the input selector on the amplifier. By this way, we expect to have fast switching time to compare the two cables sonic quality. Am I correct? WRONG!!!
Show me my mistake!
Well, let’s start from the beginning. The signal will flow from the source to both cables. If you switch to input #1 or #2, then only will cable will send the signal to the amplifier, right? True. Then, how about the other cable? Let’s say, I switch the amplifier to input #1. The cable #1 will flow the signal from the source to the amplifier. But, on the cable #2, the signal will stuck on the end of cable. It can’t pass the signal to the amplifier because the road is blocked (the amplifier accept input from #1 only). Do you think the signal will stuck at the end of cable #2? Not really 😉
Actually, the signal at cable #2 will be sent back to the source, then transfered to cable #1. So, what you hear is the combination of cable #1 and #2 characteristic. Not the single cable characteristic. So, this is not a fair way to do a comparison of cable sonic quality. See the diagram below.
At this point, I believe you know why doing this thing will result the “near” same quality for both cables. It\’s very hard to distinguish the maximum sonic quality of each cable.
A Better and Fair Methodology
After cosidering few things, I think the best methodology is to use selector on both ends. I mean that we use selector on the output of the source and at the input of the amplifier/pre-amplifier. So, when we want to test cable #1, we have to select Out #1 and Input #1. By doing this way, we can guarantee that the signal will be transfered to single cable only (cable #1 for this case) and make sure the cable #2 is totally disconnected (no reverse signal, so interference, and vice versa). The diagram should be like picture below.
Usually, the source has no output selector. So we have to build them manually. Use highest grade components (for the switch and the internal wiring). Shortest wiring is mandatory to produce less bad effect or coloration. Typical pre-amplifier/amplifier usually has input selector. So, we don’t have to add extra selector for this part. Happy benchmarking!