Should I try to sum this all up, including some small additions?
Here we go...
POWER CABLE:
Here, the problem is power noise making it's way through to the audio lines. Can either be the rubbish superimposed on our 50Hz/60Hz power sine, leaking through a device's PSU into the audio circuit - or both noise and the sine itself (the latter labelled as "hum" in this case) coupling from the mains into audio cables.
-- Special power cables simply inserted between mains outlet and gear will not make a difference in a balanced environment with a good wiring scheme, since the major noise contribution is coming from outside the studio, and a piece of passive cable will do nothing to remove it before it enters your gear's PSU.
-- In an environment with unbalanced lines and/or poor wiring scheme, you may get coupling of AC hum & noise into your audio lines, thus a special power cord migh help if it is twisted-pair, wich reduces the electromagnetic field.
-- If you have a central power conditioning device in your studio (reducing incoming noise), a special power cable between that device and your gear might prevent noise from within your studio from contaminating your (now relatively clean) mains power - and thus from entering your gear's PSU. Depending on the functional scheme of the power conditioner, you may however not notice an improvement by fancy cable if the conditioner filters both incoming mains AND the output to your studio.
Bottom line: Special power cabling may have an effect in audio systems containing compromised (or at least non-optimal) wiring or gear's PSU's, but it's rather unlikely to improve systems containing properly designed gear and wiring schemes in the first place.
AUDIO CABLE:
Here, the main problem is a possible degradation in sound quality due to interaction of devices' output- and input impedance (Z) with the cable's parasitic impedances (= ohmic resistance, inductance, capacitance).
-- High impedance sources, especially those with inductive components as found in pickups (e.g. guitars, basses, rhodes pianos etc.) will interact heavily with the cable capacitance, with effects already explained in this thread. The less cable capacitance, the shorter the cable, and the higher the i/p Z of the following device, the more of the original HF content will be transmitted.
-- The lower Z.in & Z.out, the disproportionally longer a cable would have to be for the cable capacitance to sum up to an amount as to produce an audible HF roll-off. For a roll-off at 20KHz in a low impedance line (Z.out < 50 R, Z.in < 1K), this would have to be around 100m for a good quality cable.
-- With cable runs as long as described above, transformer-coupled gear (= a good deal of the Z being inductive), even though low-impedance, may exhibit HF peaks, due to the mechanism described for high Z lines. Depends on the individual transformer construction, though.
-- The resistive part of a cable's impedance is negligible for mic/line/instrument applications, since Z.in/out of the connected devices form the dominant parts in this respect.
A side-note to noise rejection of audio cables regarding construction of twisted pair and shielding:
--The level of CMRR is mainly provided by the i/p & o/p devices, but may be affected by the cable to some degree. The higher the ratio of twists (of the hot&cold leads) per length unit, the less the degrading of CMRR by the cable. Beyond a certain point, though, this becomes economically unjustifiable
--In areas with high RFI, noise might enter through the cable into devices with high impedance internal circuits (e.g. tube mic's) although their Z.out itself is medium (around 200 R). Therefore, even around the 1950/60ies, e.g. manufacturers like Neumann came up with a double shielded cable, with the two shield layers being woven differently.
PS.
Jim, regarding your 2 inch wire replacement in condenser mic's -- that would have to be between capsule and fet/tube input? So you're talking about the dielectric properties of the cable's insulation, with the capacitive parts formed by the wire and the metal surroundings that the cable runs through?
Regards
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Topic: Wire , Can you really hear the difference? (Read 19115 times)