Unbalanced | Balanced
Unbalanced connections have two
conductors, one at ground potential and the other carrying signal.
Equipment operating at -10 dBv invariably uses unbalanced connections.
Balanced connections use two
conductors, each which carries the same signal but with the polarity
of one reversed with respect to the other. Balanced connections may
or may not be referred to ground. If not, they are referred to as
floating connections. A balanced connection referred to ground
requires three conductors, the third having ground potential.
In sound reinforcment and
recording evironments, balanced connections are preferable to
unbalanced because they are far less susceptible to interference.
Also many feel that the redundancy of two signal conductors carrying
audio yields better quality audio.
Good cables and connectors
Not all cables and connectors are
the same. Good connectors will have low contact resistance and well
supported strain relief. Products like Whirlwind, Switchcraft and
Neutric have been the industry standard for years. All brands offer
quality products for equipment interfacing.
- So what about cables? Cables
can play a big roll on the quality of your audio signal. Even if the
diameter, wire gauge, and general construction are similar, two
cables may have significantly different electrical and physical
properties such as resistance, capacitance between conductors,
inductance between conductors, over all flexibility, shielding
density, durability, ability to withstand crushing or sharp bends,
tensile strength, jacket friction, and so forth.
- The best shielding you can
use is foil shield, but such cables are not particulary strong and
the shielding can deteriorate if they are flexed too much. Foil
shielding is most often used in permanent installs and within racks
where cable movement is minimal. Braided and wrapped cable is most
often used for mic and instrument cables. Braided is preferred over
wrapped because wrapped tends to open when flexing. This only
degrades the shielding density and can also cause microphone noise.
- If the cable capacitance
changes when you flex it, this can change the induced noise level,
and the cable is said to be microphonic. This can be a big problem
with phantom power in mic cables, it can happen in any cable though.
Avoid this problem by using cables with stable dielectric
(insulating) material, and with a tightly braided shield that is
well-trapped by the outer jacket so the shield itself doesn't open up
as the cable is flexed.
Shielding adds capacitance, bulk,
weight, and cost to a cable, but never consider using unshielded
cable for instruments or microphones.
- Speaker signal is different.
The signal level is so high in speaker cables that electromagnetic
noise is insignifcant in comparison so unshielded cable is fine. In
fact, the higher reactance of shielded speaker cables can induce
deleterious parasitc oscillation.
infomation provided by Yamaha