Cables: what actually matters
Interconnects, speaker cables, digital links, mains leads
A cable cannot improve a signal, only degrade it more or less. The measurable parameters are geometry (capacitance, inductance), shielding quality, contact reliability and length. That is already plenty: badly chosen cables cost treble, inject noise and create ground loops.
Analogue links: RCA or XLR
Unbalanced (RCA) runs should stay short: past 1.5-2 m, cable capacitance starts interacting with the source's output impedance, costing treble and picking up more noise.
Balanced (XLR) between genuinely balanced devices handles 5 to 10 m with ease, and common-mode rejection removes most induced noise. An XLR on an artificially balanced output gives none of that benefit.
For a phono cartridge, total capacitance (cable + input) is a tuning parameter, not a detail: a MM typically wants 100 to 300 pF total, while a MC mainly cares about loading resistance.
Speaker cables
Gauge sets the loss: 2.5 mm² is fine to 3-4 m into 4 ohms; beyond 5 m move to 4 mm². Cable resistance above 5 % of the speaker impedance degrades damping factor.
Keep both runs the same length even if one side is closer. A 2 m difference is not audible in itself but complicates later diagnosis.
Very high-capacitance geometries can destabilise some amplifiers (notably class D or high-feedback designs): an amp running hot or hissing after a cable change is a warning.
Digital links
Coaxial S/PDIF: keep 75 ohms end to end, connectors included, and prefer 1.5 m over 50 cm when possible — impedance reflections settle better over a longer run.
Toslink optical isolates galvanically (useful against ground loops) but remains jitter-sensitive and bandwidth-limited over long plastic runs.
USB: the critical points are the 5 V rail and high-frequency noise, not bit transmission. A split-power cable or a galvanic isolator solves more than an exotic conductor. I2S over HDMI is proprietary: verify pinout compatibility between both devices.
Routing and contacts
Separate mains leads from interconnects; cross at 90° when needed. Avoid coiled loops, which behave like antennas.
Clean contacts at least once a year: re-seating plugs often restores clarity wrongly blamed on components.
Do not over-tighten bananas into plastic binding posts, and check that no stray strand bridges the terminals.
Common mistakes
- Spending on cables before optimising placement and mains.
- 5 m RCA runs from a high-output-impedance source.
- Undersized speaker cable on long runs.
- Mains leads coiled together with interconnects behind the rack.
Checklist
- Interconnect lengths minimised and matched per pair.
- Speaker cable gauge matched to length and impedance.
- 75 ohm coax respected end to end.
- USB power and ground addressed if noise appears.
- Mains and analogue routing separated, contacts clean.