Why we stock OFC, and what 7N actually means

Every cable listing you have ever read says OFC. Most also carry a number-and-letter code — 4N, 6N, 7N — that sounds like a purity arms race. Here is what it actually means, without the marketing department in the room.

OFC is oxygen-free copper: copper refined so that almost no oxygen remains in the metal, typically 99.95% pure or better. Less oxygen means fewer oxides inside the conductor, which matters mostly for how the wire ages and how cleanly it draws into fine strands — not because oxygen audibly "blocks" your music.

The N-count is the number of nines. 4N is 99.99% pure, 6N is 99.9999%, 7N adds another decimal of ceremony. The conductivity difference between 4N and 7N copper is measured in fractions of a percent — far below anything that survives a blind test through a headphone driver.

So why do we stock it? Because purity correlates with process control. The mills producing 6N and 7N copper also draw more consistent strands, anneal more carefully, and reject more defects. You are paying for manufacturing discipline, and that shows up in flexibility, corrosion resistance, and how the wire behaves at the solder joint years later.

Where should the money go instead? Geometry (star-quad rejects noise better than purity ever will), shielding, strain relief, and the connectors at each end. A €40 rhodium Furutech on 4N wire beats a €2 plug on 7N wire every day of the week — that is the order of operations we build by.