The Sound of Interconnects

Nothing is more controversial and bound to draw fire than the mention of the word interconnects in an audiophile forum. The audio industry uses hype marketing and predatory tactics to lure consumers into buying what they call "superior" audio cables. As I am getting the finishing touches put on my personal audio system, I am getting close to starting to look at cabling but more so from a convenience standpoint vs. good sound. A fellow audiophile stopped over to pick up a cartridge he had purchased and dropped off some interconnects and asked if I would audition them. I kept me comments to myself but agreed to oblige. To make the test as transparent as possible, I put my DAC in variable output mode and plugged it directly into my 45 SET amp using only a single interconnect in the audio path. I was floored at what I heard!

Prior to this I was in the camp of physics where electrons bump electrons, etc. and unless there is a major flaw in the design of the cable, there should be no perceived difference in sound. This listening test was proving otherwise! I invited a few other fellow audiophiles over and they too drew the same conclusions. The new cable had more detail, and extended treble and bass notes. The largest improvement was the coherence of the music wherein you can hear the signal move as the artist plays up and down the piano keyboard. For all practical purposes I will attribute that to detail but it greatly improved the listening experience so I'll take it!

Now the engineer in me started stepping in ... what am I hearing? The cables I was asked to audition used the popular "bullet-style" RCA connectors so I was curious if that played a factor so I ordered some "The Natural One" interconnects from Parts Connexion to throw in the mix along with my tried and true Blue Jeans Cables and some cheap Monoprice cables I had picked up for testing and repairing gear. Before any testing began, I spent several hours listening and swapping cables and I ranked them in this order from best to worst:

- Noteworthy Acoustics prototype

- The Natural One (KLEI)

- Monoprice Premium

- Blue Jeans Cable (LC-1)

*NOTE: All cables are either 3' or 1m in length

Next I put the cables on my DE-5000 to measure their electrical characteristics so I could quantify exactly "what" I was hearing. The typical characteristics of any cable are series resistance (Rs), series inductance (Ls) and parallel capacitance (Cp). I'll save the boring electronics theory lecture and let you Google the meaning and effects on your own time. Here are the results:

This was interesting! My ranking almost lined-up with series resistance (almost!) Capacitance did not seem to be a factor and inductance was too close to call. Then I wondered how these parameters change across frequency, so I tested them again on the LCR meter at 100Hz, 1kHz and 10kHz:

Hmmm ... well that was pretty inconclusive! It still did not explain why my ears preferred The Natural One over the Monoprice by a significant margin. I recently picked up a Parts Express DATS v3 that is capable of measuring impedance as it sweeps frequency and is used to characterize speakers so I thought let's give that a try:

This too was a bit inconclusive and mirrored the static LCR measurements I had taken. It was, however, interesting to note that impedance increases with frequency at about 2-3kHz regardless of the cable. I was still puzzled why I preferred The Natural One over the Monoprice. After a few minutes it dawned on me that both The Natural One and the Noteworthy utilized the KLEI "bullet-style" RCA connectors. The theory is to provide a single point of contact on the RCA shield instead of a slip-fit around the perimeter. The slip-fit gets loose with age and is prone to oxidation. The KLEI is a very snug fit so one would assume it makes a good connection. I plugged the cables into a gold-plated, chassis mount RCA connector and measured series resistance from connector shield to connector shield on the LCR meter:

Eureka! The KLEI does in fact reduce the impedance of the shield by almost 2x that of a standard RCA barrel shield. If I factor that into the equation, now my ranking lines up directly with imperical impedance of the interconnect system. The lower the impedance, the better the cable sounds! This makes sense because resistance (impedance) is the resistance to the flow of electrons. It also goes to show that you don't have to spend a fortune to get a decent sounding cable. The Monoprice Premium sounded and tested very good and only cost $4.09 for a 3' pair!

As an aside, I was curious why the capacitance of The Natural One was so high. I discussed the cable with Chris at Parts Connexion and the cable is a twisted 2-wire pair with a separate braided shield. He only terminates the shield to ground at one end of the cable hence there is a capacitance build-up of energy across the distance of the cable. This is common practice that I use almost every day as an electrical engineer to reduce EMC/EMI when interconnecting two electronic devices with a shielded wire. You always bond the shield at the driving end of the cable and let it float at the receiving end. The other caveat here is that if you are using a cable with high capacitance to connect your moving magnet (MM) phono cartridge to your phono preamplifier, make sure the cable capacitance plus the phono preamplifier input capacitance matches your cartridge recommendation. Many people forget to include cable capacitance into this equation.