Quick Answer / Summary: Jack-to-jack leads extend a plug-ended cable or join two plugs. Jack-to-plug leads change gender, connecting a socket-ended device to a plug-ended one. Both are available pre-made in fixed lengths and gauges. Check continuity on both conductors and pull-test the ends before putting a lead into service.
A banana jack cable has a socket at one or both ends instead of a plug. The configuration decides what it can join, and the difference between jack-to-jack and jack-to-plug is the difference between an extension and a gender change.
The Configurations
Four combinations exist: plug-plug, plug-jack, jack-jack and jack-bare. Plug-plug is the standard speaker lead; plug-jack extends it; jack-jack joins two plug-ended leads; jack-bare terminates in wire for a permanent connection. Each adds a different number of interfaces to the circuit.
Counting Interfaces
A plug-plug lead has two contacts. Adding a jack-to-jack extension makes four, and each one can loosen. Where a long run is needed, a single long lead with two plugs is better than two leads joined.
Gender Change Versus Extension
A jack-to-plug lead does not extend length so much as change what the end accepts. Buying one to extend a run usually results in an unintended gender change at one end.
Gauge, Length and Inspection
Pre-made jack cables state a gauge, and it is often lighter than the plug suggests. Check the printed figure on the cable rather than the packaging. Length adds resistance, and a long light lead behaves like a thinner gauge over the run – the same arithmetic as any speaker cable.
Continuity and Pull Test
Check both conductors end to end and pull-test each termination. A lead that fails either is not fit for service, whatever its appearance, and pre-made leads are not immune to assembly faults.
Labelling Both Ends
A jack-to-jack lead has identical ends, so labelling matters: mark which end goes to the amplifier. Without it, a lead can be connected backwards in a way that is impossible to see.
Storage and Coiling
Coil a lead loosely and tie it without a tight bend at either end. Tight coiling trains the cable into a set and concentrates stress at the terminations, which is where these leads fail.
Configuration Guide
| Configuration | Joins | Interfaces Added |
|---|---|---|
| Plug to plug | Two sockets | None, standard lead |
| Plug to jack | Socket to socket | One gender change |
| Jack to jack | Two plugs | Two contacts |
| Jack to bare | Socket to terminal | One contact |
| Long run | One long lead | Fewest interfaces |
Practical Applications
Extending a speaker lead temporarily, connecting a socket-ended device to a plug-ended cable, choosing between an extension and a longer lead, and inspecting pre-made leads before use.
Frequently Asked Questions
What is a banana jack cable?
A lead with a 4 mm socket at one or both ends, used to extend a plug-ended cable or to change gender between a socket and a plug.
Should I extend a lead or buy a longer one?
Buy a longer one where possible. Each extension adds two contact interfaces, and the interfaces are where intermittent faults appear.
How do I check a pre-made banana lead?
Continuity on both conductors end to end, plus a pull test at each termination. Reject any lead that fails either check.