System Cable Capacitance Question from a New Audiophile

Al, thanks again for the explanation. I find the impedance interactions fascinating even if I do not completely understand them. I’ll read up on that link. I really like the clarity of passives but have concerns about the impedance swings having audible affects on the system.

Last night I was doing some critical listening with my Roomate and we both agreed that while using the sys, the most dynamic sound was when the volume was set under 35-40% on the knob. The system played much louder but micro dynamics in the music seemed to slowly roll off.

That being said, I’ve been trying to figure out which kind of passive volume control I want to implement as an upgrade to the sys. I came across the Tortuga L3.V25 which is an LDR device and lets the user calibrate the preamp and set specific output impedance to test for a value that works best in ones system. This seems like an interesting option.

I know this thread has deviated from the initial post, I should have perhaps clarified my initial point but sometimes you never know where these threads will go! Appreciate the time and thoughts Al.

Blue jeans LC 1 interconnect ++1, I use expensive ic but this cable is almost 90% of what my highend Cables and it’s only $37.

AJ, based on comments I’ve seen in the past and on its description and specs I suspect the Tortuga L3.V25 would be an excellent choice. And as you mentioned its user-configurable impedance is a great feature, especially given the uncertainty about the output impedance of your phono stage. It wouldn’t surprise me, though, if the Tortuga’s default setting of 20K turned out to be optimal.

Regarding your finding that volume control settings on the Sys that were below 35-40% provided best dynamics, I don’t find that to be surprising. In addition to the subjective effects of volume changes on perceived dynamics, that setting will result in a significantly lower output impedance than the maximum value the impedance would reach at a much higher setting. And hence less effect on high frequencies due to interaction of that output impedance with the capacitance of the preamp-to-power amp cable than at that higher setting.

In that regard, I’ll add to my earlier statement that...

In the case of a resistance-based passive preamp output impedance will tend to be highest when its volume control is set somewhere in the middle part of its resistance range, and lower than that when it is set closer to either of its extremes. Exactly where the highest impedance occurs will depend on the output impedance of the source.

... "the middle part of its resistance range," corresponds to a volume level that is only about 6 db less than max. Which for a typical rotary volume control probably corresponds to only around 45 degrees of rotation below the maximum setting. So the relatively low output impedance of the Sys that presumably occurs at the max volume setting (assuming low source impedance) will increase very rapidly to its max value as the control is turned down from that position, but will progressively decrease from there at progressively lower settings, and will be significantly less than its maximum value at or below 35-40%.

Finally, regarding BlueJeans LC-1 which two of the others suggested, note that it has particularly low capacitance (only 12.2 pf/foot), much lower than the capacitance of many cables that are vastly more expensive! Signal Cable also makes modestly priced good quality interconnect cables having capacitances that are almost as low.

Regards,
-- Al