Long XLR's: PAD Venustas versus Mogami

06-07-11: Madfloyd
So capacitance is the main parameter to consider for longer runs (where the lower the better)?

Capacitance and shielding, although the significance of shielding is lessened if the interface is balanced.

Shielding will affect susceptibility to both noise pickup caused by rfi/emi, and ground loop-induced hum and noise. The likelihood of both of those things becoming an issue increases if the cable length is long. Some cable designs achieve increased shielding effectiveness at the expense of increased capacitance, so there may be a tradeoff that has to be considered.

As far as lower capacitance being better is concerned, what matters (if you want neutral behavior, as opposed to a softened upper treble) is that the capacitance has to be low in relation to the output impedance (at high frequencies) of the component driving the cable. Reducing capacitance beyond that point would be overkill.

That can be calculated. Determine the capacitance C of the total length of cable, based on its specs. Calculate its capacitive reactance Xc (the capacitive form of impedance, measured in ohms) at 20kHz, based on the formula

Xc = 1/(2 x pi x F x C)

where Xc is capacitive reactance in ohms, pi = 3.14, F is frequency in Hertz, and C is the capacitance of the total length of cable in farads (1 farad = 1 trillion pf). As long as Xc is much higher (say 5 or 10 times or more) than the output impedance at high frequencies of the component driving the cable, you are good to go, as far as capacitance is concerned.

All of this applies, btw, just to line-level analog interconnects. Speaker cables, phono cables, digital cables, etc. are a different story altogether.

Regards,
-- Al

Al,

THanks for the insight.

Unlike the BAt preamp, the einstein has output imped. 100ohm and it also does not rise at bass freq. According to the equation, I should be able to use cables of higher capacitance (Mogami) without audible roll off. In practise, the Mogami sounds quite rolled off. What other things do you think are at play there?

06-07-11: Glai
According to the equation, I should be able to use cables of higher capacitance (Mogami) without audible roll off. In practise, the Mogami sounds quite rolled off. What other things do you think are at play there?

Don't know. I'd just put it in the category of cable effects that are technically unexplainable.

If you had an unbalanced interface, I would have speculated that perhaps the Mogami's excellent noise rejection capabilities might be introducing less low level background noise onto the signal than the cable(s) you are comparing to, at upper treble or lower ultrasonic frequencies. I've read a number of times that very low level high frequency noise can subjectively be perceived as increased "air" and ambience. But I doubt that that kind of effect would be at play in the case of a balanced interface.

Best regards,
-- Al

In case anyone missed it...I recently had a bad (relatively) experience with some new 1 meter Mogami Neglex/Neutrik terminated balanced cables...they were surprisingly unlistenable in my system (Kavent S33, Forte' Model 55), and this is after using Mogami for mic cables for many years. Go figure. I suppose I should have waited for a "break-in" period but it was just too unbearable even for that...replaced 'em with Audioquest Diamondbacks and they are so much better I just bought a second pair to connect my DAC to the balanced pream inputs.