Connections & formats
6.35mm
Also called 1/4 inch, quarter-inch jack, 6.3mm
The 6.35mm jack, also called a quarter-inch plug, is the large headphone connector found on desktop amplifiers, receivers, mixers and musical instruments. As a headphone connector it is single-ended and carries the same stereo signal as a 3.5mm plug, on a sturdier body.
The size dates from telephone switchboards and has outlasted almost every other audio connector. It stays on home and studio gear because it is robust, easy to repair and easy to plug in by feel.
For headphones it is electrically the same as the 3.5mm mini jack: tip, ring and sleeve for left, right and ground, so simple adapters go either way, and many headphones ship with one screwed onto a 3.5mm plug. On studio gear the same TRS plug often carries one Balanced vs single-ended mono line signal, and instruments use a two-contact mono version.
Hi-fi amplifiers and receivers almost always use this size for their headphone output, while portable gear uses 3.5mm or 4.4mm.
Where you’ll see this on tonistry.
- 6.35mm (1/4") is one of the connection types members pick when they draw a signal chain.