For instance, a 1m Schroeder Method setup has a source seeing an impedance like a 2m cable. Obviously the longer the interconnect the more potential for an impedance problem for a source’s output.
Doug, yes, I certainly agree with the second sentence, but the first sentence isn’t quite correct.
Doubling a cable in the manner you’ve defined (i.e., two identical cables connected in parallel) will double the capacitance, while cutting inductance, resistance, and
"characteristic impedance" approximately in half. In contrast, doubling the length of a single cable will double capacitance, inductance, and resistance, and leave characteristic impedance unchanged.
Regarding your wise cautions about the slight possibility of equipment damage, the one concern I would cite in particular would be in the case of speaker cables, if the particular cables have high capacitance per unit length and/or if their length is especially long. The resulting heavy capacitive load could cause some amplifiers, especially solid state amps, to oscillate. I would be very surprised, though, if oscillations were to result from the doubling of an interconnect cable connecting a preamp to an amp.
Also, I have no way to predict what might result from doubling interconnects or speaker cables which incorporate a "network box," such as MIT and Transparent cables, because I’ve never seen a technical definition of what is in those boxes.
Regarding the possibility of adverse sonic effects that might result from doubling a cable, as opposed to the possibility of damage, I would cite the following situations as being susceptible:
(1) The situation I referred to above, involving speaker cables that have high capacitance per unit length and/or are especially long. The resulting increase in capacitance might adversely affect the sonics of an amplifier while not being severe enough to cause an oscillation.
(2) All digital interconnect cables. As I stated earlier in the thread I recommend against doubling cables conducting digital signals, regardless of how pleasing the results may seem to be, because the resulting mismatch of the cable’s characteristic impedance with the impedances of the components being connected amounts to introduction of a known and explainable design flaw into the system.
(3) Line-level analog interconnect cables that are especially long and/or have high capacitance per unit length **and** are driven by a component having high output impedance. That combination of circumstances may introduce rolloff and/or undesirable phase shifts in the upper treble region. This possibility applies to the outputs of some DACs, as you stated, as well as to the outputs of some other source components and some preamps.
(4) Phono cables used with moving magnet or high output moving coil cartridges, unless the cartridge manufacturer recommends a particularly high capacitive load (for example, 400 or 500 pf) for the particular cartridge.
Regards,
-- Al
