THE DECKS WILL NOT LINK

These are AlphaTheta's four checks, in their order, and the order is not where a DJ would start.

AlphaTheta publish four checks and the player number is the first of them: "Check that the player number has been set correctly." Then the cable: "Check that the LAN cable is correctly connected to the LINK terminal." Then the hub: "Check that the power of the switching hub is turned on." And finally what else is on it: "Disconnect unnecessary devices, if any, from the switching hub."

The player number leads for a reason. Two decks claiming the same number is the classic booth fault, and it is invisible: each deck looks perfectly normal on its own. It happens the moment somebody sets a number by hand, or swaps a deck in from another room.

The LINK terminal is not the only LAN socket on the gear. Some units carry more than one and they do different jobs, which is why AlphaTheta say the LINK terminal rather than the LAN socket. Your model's page in this catalogue names its sockets.

And the last check is the one people skip. Taking unnecessary devices off the switching hub is not tidiness. A booth hub with a lighting desk, a laptop on club wifi and a spare cable hanging in it is a busier network than the one AlphaTheta designed for.

Start here, because it is not a fault. PRO DJ LINK works when rekordbox is in EXPORT mode. It does not work in PERFORMANCE mode. AlphaTheta state that first, before any fault, which makes it the likeliest reason a LINK button never appears at all.

If you are in EXPORT mode and it still does not appear, AlphaTheta publish five computer-side causes and every one of them is on your laptop rather than in the booth.

• The firewall, and it is four programs. AlphaTheta name the four programs security software has to be allowing, and a DJ who allows only the first one still has no network: the rekordbox program file, ProDJ Link System Manager, ProDJ Link NFS Server, and edb_streamd.
• A second network. AlphaTheta state that "PRO DJ LINK may fail to run properly if your computer is connected to multiple networks", and ask for unused networks to be disabled or their precedence changed. A laptop on club wifi and a LAN cable at the same time is two networks.
• A port already taken. AlphaTheta state that "PRO DJ LINK may fail to run properly if the Port used by rekordbox for PRO DJ LINK is being used by another application", and ask for the conflicting service to be closed.
• Internet Sharing. AlphaTheta state that "PRO DJ LINK may fail to run properly if Internet Sharing is enabled", and ask for it to be turned off.
• The order things were switched on. AlphaTheta state that when a router sits on the PRO DJ LINK network, "the network may fail to be established properly depending on the order" the devices are powered on, and ask for the router to be powered first or taken off the network entirely.

Read that list again as a travelling DJ. Four of the five are things a laptop does differently in a club than at home, which is exactly why LINK works in your bedroom and fails at the venue.

On a CDJ-2000 or a CDJ-900, AlphaTheta publish a firmware floor for linking: the version in the unit "may not be supported", and the instruction is to update the CDJ to Ver. 4.00 or later.

This is worth knowing before you rewire a booth, because a CDJ-2000 or CDJ-900 that has never been updated is still extremely common in clubs, and no amount of cable swapping fixes a firmware floor. Check the version on the deck against the firmware page here.

Do the two that cost nothing and take ten seconds: check that no two decks share a player number, and move the LAN cable to a different port on the hub.

If it still will not come up, stop. PRO DJ LINK is a convenience, not the set. Every deck in that booth plays from its own USB drive with no network at all. You lose the shared library, the linked waveforms and the shared beat grid. You do not lose the gig, and a DJ crawling behind a rack with ten minutes to go loses more than he gains.

Put a drive in each player, play, and sort the network out tomorrow.