Quick Answer / Summary: For line-level interconnects: choose shielded construction, keep capacitance low (commonly 50-150 pF per metre), and keep runs short. Match the connector to the equipment – RCA for domestic unbalanced, XLR for balanced studio runs. Avoid running interconnects parallel to mains cables for long distances, and never substitute speaker cable for an interconnect.
Interconnects carry the small signals between source, preamplifier and power amplifier, and they live or die on two parameters: shielding and capacitance. Gauge, the hero of speaker cable, barely matters here – which is why an interconnect purchase follows different rules.
Why Line Level Is Different
A line-level signal arrives at roughly one volt into an input of thousands of ohms. The cable’s series resistance is negligible against that load, so gauge is irrelevant; the shield’s job is to keep interference out of a high-impedance circuit, and capacitance’s job is to preserve high frequencies across the run. Every interconnect decision reduces to those two, plus the connector.
Shielding Constructions
Foil plus drain wire gives excellent coverage for fixed installations but is less flexible. Spiral or braided shields survive flexing and are the practical choice for leads that get moved. For short domestic runs, both work; for runs near dimmers or mains cable, coverage percentage is the number to compare.
Capacitance and Run Length
Capacitance forms a low-pass filter with the source’s output impedance. With a typical source, a few metres of ordinary cable is transparent; at ten metres or more, a high-capacitance lead starts to roll off the top end. The rule: short runs, stated capacitance, and no long parallel routes beside mains.
Connectors, Grounding and Hum
RCA connectors are the domestic standard for unbalanced line level; XLR carries balanced signals for studio runs. In both cases the shield must connect at both ends for a domestic unbalanced lead – the exception being designs that deliberately lift one end to break a ground loop in complex installations. Hum that appears only when a particular source is connected is a grounding question, not a cable-quality question.
Diagnosing Hum in Three Steps
First, disconnect sources one at a time to find the contributor. Second, try the same lead in a different position to rule out a bad connector. Third, where two grounded devices disagree, a ground-loop isolator on the line-level lead solves what no amount of cable upgrading will.
Building a Reference Set
Keep one known-good interconnect of each connector type and length as a reference. When a channel misbehaves, substituting the reference isolates cable from equipment in under a minute – the single most useful habit in audio troubleshooting.
One Reference Lead per Connector Type
Keep a known-good lead of each connector type and length. When a channel misbehaves, substituting the reference isolates cable from equipment in under a minute – the single most useful habit in audio troubleshooting, and the cheapest.
Interconnect Selection Card
| Parameter | Target | Why |
|---|---|---|
| Construction | Shielded | High-impedance circuit picks up noise |
| Capacitance | 50-150 pF/m, lower for long runs | High-frequency roll-off |
| Length | As short as routing allows | Capacitance and pickup |
| Connector | RCA unbalanced, XLR balanced | Match the equipment |
| Routing | Away from mains cable | Induced hum |
Practical Applications
Connecting a DAC to an integrated amplifier, wiring a pre-power pair, replacing a hum-prone lead, and assembling a reference set for troubleshooting.
Frequently Asked Questions
Do interconnect cables need thick conductors?
No – line level into a high-impedance input makes resistance negligible. Shielding and capacitance decide performance, not gauge.
How long can an RCA interconnect run?
A few metres is comfortable for ordinary cable; beyond about ten metres, choose low capacitance and consider a balanced connection if the equipment supports it.
Why does hum appear only with one source connected?
A ground loop between that device and the rest of the system. Try a ground-loop isolator on its lead, or connect the source to the same outlet circuit as the amplifier.