Two-channel Stereo sound can be provided by two Mono cables, or a single Stereo cable.

What differences, whether significant or not, are there between pairing each voltage lead with its own ground lead versus sharing a single ground lead between [an arbitrarily large number of] audio channels?

Below I include details of my thoughts that raised the question.

Mono cables each transmit one channel and each have two leads: voltage and ground. Using mono cables, the number of channels (N) can be increased arbitrarily by using a matching number of N Mono cables, for a total of 2N leads.

Each Stereo cable can by itself provide two audio channels with only three leads: voltage L, voltage R, and a single ground lead (shared between channels L and R), effectively providing the same throughput with one less lead than the Mono configuration, which makes me wonder what [functionally inconsequential] differences there are between 1 x Stereo quality vs 2 x Mono quality.

Furthermore, 4-lead cables (such as stereo headphones + mic over a single bus) provide 3 channels using 4 leads: voltage L, voltage R, voltage M (mic), and one single ground lead shared by all three channels!

Assuming there is no quality loss when channels share a ground lead, then a Mono-only multi-channel configuration wastes half its leads save one (N-1).

  • Once you're inside the amp., isn't it all grounded to the chassis anyway?
    – Tim
    Dec 20 '14 at 8:16

There is no significant difference between two unbalanced mono connections and a single stereo connection. However, with two mono lines you have the option of making both balanced, which is usually a good idea for longer connections. With single-cable stereo, this is typically not possible because suitable 5-lead connectors aren't available (at least not widespread).

  • Would you delve more deeply into the concept of 'balance' please? I am fairly certain am missing some key factor in understanding what you mean exactly. Dec 25 '14 at 14:51
  • 1
    In professionell sound balanced cables are used. The signal is sent as one hot and one cold. The cold is inverted compared to the hot. Ground is only used for the sceeen. For microphones the connectors are generally three pin XLR ( personally I preferr the Neutrik brand ). The Calle and connectors can additionally be used to provade phantom power to the microphone at 48Volt and a few milliamps. For stereo mics we tend to use 5pin XLR contacts and 4 wire plus screen cable but there are a number of variants.
    – ghellquist
    Oct 6 '19 at 17:09

Most RCA stereo cables are 4-lead, and consist of 2 mono cables connected only by their outer insulation. This type of cable usually has a figure-8 crosssection. Every signal wire has its own ground in a coax configuration: signal wire in the middle, and the ground as a shield around it. This is done to reduce crosstalk.

3-lead stereo cables are used in some headphones (usually small in-ear types), in DIN cables (long obsolete), and maybe SCART (also obsolete). These have two signal wires with the ground wrapped around both of them. Because the two signals are not separated by a ground, they are more susceptible to crosstalk (signal from one channel leaking into the other) than dual-mono cables.

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