Cable comparison, part 2
Tonight I did a blind test using the two cables mentioned previously.
The one I liked better in the non-blind tests is a Quantum EPI. This is made from Quantum 2300 cable with gold-plated G&H ends. The other cable was built for me by Blue Jeans Cables from Belden 1800F with nickel-plated Neutrik ends.
I was blindfolded. We started with both cables unplugged. Mary-Suzanne picked one cable and connected it to the guitar and the GT-8. I played, listening for the same cues I had heard in the non-blind test a week ago. I stopped playing, Mary-Suzanne switched the cables, and I auditioned the other cable. We did this twice, alternating cables with each test. Only the starting cable was randomized. At the end of the second test, I correctly identified that I was playing through the Quantum cable. I was fairly certain of the identity on first round; I asked for the second round to be certain of what I was hearing.
This tells me that I don't have to see the cable to identify it. As I noted before, there's an obvious clarity in the upper harmonics when using the Quantum cable. I also noted a more distinct and open tone in the lower registers. I heard this while blindfolded and identified the cable based upon that "signature."
I still don't know for sure why those cables sound so obviously different. The capacitance measurements are very close: 510 pf vs. 575 pf. If I wanted to be very careful about this experiment I'd have to trim the higher-capacitance cable to match. At this point, I'm just not that motivated. Note that the Quantum cable probably has a higher capacitance per unit length - it's the shorter of the two cables under test.
Furthermore, 65 pf in this context is quite a small change. The total circuit capacitance gets contributions from the interwinding capacitance of the pickup and the capacitance presented by the input stage of the GT-8; the 65 pf delta almost certainly represents a less than 10 percent change in the total capacitance. That should cause only a 5 percent change in resonant frequency. Guessing that the resonant frequency is somewhere in the mid 3 KHz range, we're talking about a difference of a couple hundred Hz.
Is that audible? Possibly. Again, I'd have to control the capacitance to rule out a simple EQ shift as the cause of the cable's signature.
What else? I suppose my blindfolded identification could have been a lucky guess. On the other hand, I clearly recognized the signature sound that I had heard a week earlier. I'm fairly confident that I could repeat the test with the same outcome, and may attempt to do so at some point. As I said, the identification wasn't a guess. I recognized the cable by its sound.
At any rate, this experiment raises more concerns. If small differences in capacitance really are significant to one's perceptions of the differences between two cables, then all instrument cable testing is inherently flawed without careful matching of total (cable plus connectors) capacitance.
At this point I'd still prefer to attribute the different sound to the small difference in capacitance between the tested cables, even though I heard the same signature when testing (non-blind) with humbucker pickups having a significantly higher resonant frequency. If there was some specific frequency that aided in my identification of the Quantum cable, it would not have been the same with the different pickup. I harbor a nagging suspicion, though, that there may be more to this than capacitance. At some future time I'll consider doing another test where the capacitance is carefully controlled to eliminate any differences.
Regardless, I'm going to stick with the Quantum cable because it sounds better to me.