"Detected existing Pro DJ Link activity on this network": why your CDJ is probably fine

You switch on, and instead of your usual screen the CDJ throws up a red pop-up: "Detected existing Pro DJ Link activity on this network, please use an alternative." The deck shows Not Loaded, rekordbox can't see it, and the decks won't link. It looks like something has broken.

In the case we've seen, nothing had. The deck has spotted another Pro DJ Link system already running on the same network and is refusing to join it. Something else on the network needs to come off. This guide walks through what to unplug, step by step.

Quick fix

• Unplug anything from the switch or router that isn't part of this booth.
• Got an Opus Quad on the same network? Unplug its LAN cable. It can't link with CDJs.
• Close rekordbox on any second laptop that's on the same network.
• Give each DJ system its own switch or router.
• Switch all decks off, then power them on one at a time so player numbers re-allocate.
• Check no two decks share a player number.

What the message actually means

Pro DJ Link is how Pioneer DJ and AlphaTheta players, mixers and rekordbox talk to each other over a network cable. They share USB libraries, beat information and player numbers. When a player powers up and finds another Pro DJ Link system already active on that network, it shows this message instead of joining in.

So the message is the deck telling you about the network, not about itself. That is why the first steps are all about what else is plugged in.

A real case we dealt with

A customer recently sent us a photo and a short video of exactly this message on a CDJ-2000NXS. The CDJ wouldn't show up in rekordbox on their Mac. On the same setup was an Opus Quad, and rekordbox was using the Opus Quad as its audio device.

The Opus Quad can't link with CDJs at all, so with both on one network the CDJ saw the other system's link activity and put up the warning. Our advice was to take everything else off the network and connect the CDJ straight to the laptop. The CDJ itself was fine. It was a setup problem, not a repair.

Step 1: Take everything else off the network

Start by unplugging every network cable that isn't part of the booth you're trying to use. Things that commonly sneak onto the same network:

• An all-in-one unit. An Opus Quad, for example, runs its own link for rekordbox and can't share it with CDJs.
• A second laptop running rekordbox, for example the next DJ getting ready, or a back-to-back setup.
• Another booth. In venues with two rooms, both systems are sometimes cabled into one network.
• Third-party software that can listen to or join the link, such as lighting control or now-playing apps.

Once the extras are off, switch the decks off and on again and see if the message has gone.

Step 2: One system, one switch

Pioneer's Pro DJ Link setup guide advises a separate router or switch for each DJ system, and no loops in the cabling. A few switch rules from the manuals and setup guide that also matter here:

• Two players can link with one cable. Three or more, or decks plus a mixer, need a switch.
• Mixers like the DJM-900NXS2, DJM-A9 and DJM-V10 have one LINK port, so they need a switch to link with two or more decks.
• Use an unmanaged switch. NXS2-era decks are happy on 100 Mbps or faster; a 1 Gbps switch is recommended for the CDJ-3000.
• Plug each deck and the mixer into the switch with one cable each.
• Never connect two ports of the same switch to each other. That loop breaks the link.
• Power the switch on first, then the decks and mixer.

Step 3: Renumber the players

Each player on the link needs its own player number. Two decks on the same number cause conflicts.

One DJ on Reddit had this exact message on an XDJ-1000MK2 in a setup with a CDJ-3000 and a DJM-V10, even with just one cable between two decks. Updating firmware didn't help. What fixed it, by their own account, was unplugging every cable, reconnecting the units one by one, and moving the players from numbers 1, 2 and 3 to 2, 3 and 4. All the link features came back, including quantised beat effects on the mixer.

To change the number:

• Remove USB sticks, SD cards and the LAN cable first. On the CDJ-2000NXS, CDJ-2000NXS2, CDJ-3000 and XDJ-1000MK2, PLAYER No. in UTILITY is greyed out while any of those are plugged in.
• Set each deck to a different number, or to AUTO.
• Reconnect one unit at a time and check each one joins.

When a deck is properly linked, its player number at the bottom left of the screen shows white. Grey or blinking means it isn't linked.

Step 4: Test the deck on its own

If the message is still there, prove the deck works by itself. Connect it with one cable straight to your laptop, with rekordbox in Export mode, and nothing else on the network. If rekordbox sees it, the deck is fine and the problem is somewhere else in your setup. Add the other units back one at a time until the message returns. The last thing you plugged in is your culprit.

Step 5: Firmware

Update the firmware on every deck and the mixer, and keep linked players on matching versions. It isn't always the answer (in the Reddit case above, updating alone didn't fix it), but it rules out known link bugs. For example, CDJ-3000 firmware 3.20 fixed a problem linking with the DJM-2000NXS.

Model notes

Opus Quad

AlphaTheta's own support FAQ says CDJ and DJM units can't be connected to the Opus Quad via Pro DJ Link. Its LINK port is for rekordbox on a computer or phone. If you want CDJs alongside it, plug them into its LINE inputs as audio and mix by ear. That's a design limit, not a fault.

XDJ-AZ

The XDJ-AZ can link up to two CDJs, but its PRO DJ LINK Mode is set to Off from the factory. Go to Utility, Mixer category, PRO DJ LINK Mode, and set it to On. Turn the AZ's Wi-Fi off, as it can't link players while Wi-Fi is in use. The CDJs become decks 3 and 4, and it needs a switch.

CDJ-3000 with older players

Mixing a CDJ-3000 with NXS2-era players brings up a notice that some Pro DJ Link features may not work due to an old model player. That one is just a warning. Only some features need every deck to be a CDJ-3000.

When it's a repair

Most of the time this message is about the network. It's worth getting the deck looked at if:

• The message appears with the deck completely on its own, with no switch and nothing else plugged in.
• After separating the systems, the deck never shows a white player number on a known-good cable.
• The link drops when you touch or wiggle the plug in that deck's LINK socket, or the plug won't click in.

The first job is proving whether the deck links normally on a clean network. If the LINK socket is worn or damaged, it can be replaced, subject to diagnosis and parts availability. A diagnostic is £30, deducted if you go ahead with the repair. Anything beyond that, we'll quote after we've looked at it. Book a repair or service here.

What to send us

Before booking anything in, message us with:

• A photo of the message on the screen.
• A photo or a list of everything plugged into the same switch or router, including any laptops.
• The model of every deck and mixer in the setup.

Often that alone shows whether it's a setup issue.

FAQ

Is my CDJ broken if it says "Detected existing Pro DJ Link activity"?

Usually not. The message means the deck has found another Pro DJ Link system on the same network. Take everything else off the network and test the deck on its own before assuming a fault.

Can I link CDJs to an Opus Quad?

No. AlphaTheta says CDJ and DJM units can't connect to the Opus Quad via Pro DJ Link. Use its LINE inputs for CDJs instead. If you need CDJs to link with an all-in-one, the XDJ-AZ can take up to two.

It worked yesterday. Why is it showing today?

Something on the network has usually changed, or the player numbers have got tangled. Unplug everything, renumber the players, and reconnect one unit at a time.

Do I need a network switch?

For two players, one cable is enough. For three or more units, or decks plus a mixer with a single LINK port, you need a switch, and each separate DJ system should have its own.

Will a firmware update fix it?

Sometimes, if a known link bug is involved, so it's worth doing. But on its own it often isn't the fix. Separating the networks and renumbering the players come first.

Still stuck after all that? Send us the photos and we'll help you work out whether it's the network or the deck. And if you're adding decks to your setup, have a look at our used Pioneer CDJs and XDJs.