The words that save gigs

The distinction underneath every other entry here. Lossy formats (MP3, AAC) permanently discard audio data to save space. Lossless formats (WAV, AIFF, FLAC, Apple Lossless) keep all of it. Converting one into the other does not restore anything: an MP3 saved as WAV is a much larger file of exactly the same audio.

The format most DJ libraries are built on. It is lossy, so data was thrown away to shrink the file and it does not come back. Players read it from 32 to 320 kbps at 44.1 or 48 kHz, which makes 320 the ceiling worth exporting. Its real advantage is reach: it plays on effectively every player you will meet in a working booth. Not literally every player ever made, the original CDJ-1000 and the CDJ-100S predate MP3 playback, but anything from the rekordbox era onwards reads it.

Lossy like MP3 but more efficient, so it holds up better at the same file size. Players read it from 16 to 320 kbps. One trap worth knowing: AAC and Apple Lossless both use the .m4a extension, so two completely different files look identical in a folder.

Uncompressed audio, nothing discarded and nothing packed down, which is why it is the largest file on the drive. Players read it at 16 or 24 bit and up to 96 kHz. Its weakness is housekeeping: artist and title travel less reliably inside a WAV than in other formats, which is why WAV libraries so often show blanks where the track information should be.

Apple’s uncompressed format. The audio is equivalent to WAV, the difference is that AIFF carries track information reliably, which is why DJs preparing large libraries often choose it over WAV.

Lossless compression: noticeably smaller than WAV, with nothing discarded, so it decodes back to the original. Documented on the CDJ-3000X up to 96 kHz, and on the CDJ-2000NXS2 up to 96 kHz and 24 bit. Older players predate the format, so confirm the deck reads it before building a booth library around it.

Apple’s equivalent of FLAC: compressed, nothing thrown away. Documented alongside FLAC on the CDJ-2000NXS2 and CDJ-3000X. It shares the .m4a extension with AAC, so the extension alone never tells you whether a file is lossless.

How much data a lossy file spends per second, written in kbps. Higher means less was discarded and the file is bigger. For MP3 the players stop at 320 kbps, which is why that number is everywhere in DJ libraries. Bit rate says nothing about WAV, AIFF, FLAC or Apple Lossless, which are not discarding anything to begin with.

The two numbers describing how finely the audio was captured, for example 44.1 kHz and 16 bit, which is CD standard. Players handle up to 96 kHz and 24 bit on the formats that carry it. Higher is not automatically better in a club: the room, the system and the mix decide far more than these two numbers do.

A high-resolution format from the audiophile world, and one of the few that simply does not play. AlphaTheta states the CDJ-2000NXS2 is not compatible with DSF or DFF files. If a track arrives in one, convert it before the gig rather than in the booth.

The hidden index rekordbox writes onto your USB next to the music: playlists, cues, grids, waveforms. When a player mounts your drive but shows no playlists, this is usually what died or mismatched, not your music. The audio files sit untouched in their folders.

The classic database format rekordbox exports to USB, the one older CDJs and XDJs read.

The newer database format, two names for the same thing, read by CDJ-3000X, CDJ-1500X, XDJ-AZ, XDJ-AN, OPUS-QUAD and OMNIS-DUO. From rekordbox 7.2.13 an export can write BOTH formats to the same stick, which is why this site anchors on that version: one export, every player. One manual step per drive comes first, right-click OneLibrary on the device and choose Convert from Device Library, as AlphaTheta sets out in its OneLibrary Compatible USB Device Export guide.

The rekordbox mode that prepares USB drives. Officially free, no subscription, confirmed by rekordbox’s own plans FAQ. PERFORMANCE mode is the other one, for playing from the laptop.

The player’s file browser. It reads your audio files directly, folder by folder, ignoring the database entirely. You lose playlists, cues and prepared waveforms; you keep the music and the gig. It is move one of the emergency list for a reason: most DJs have never tried it and do not know the audio still plays with the database gone.

File > Library > Backup Library in rekordbox 7, to a different drive or cloud. The USB in your pocket is an export, not a backup: lose the laptop library and the cues and playlists on it are the only copy left.

The file system that every Pioneer and AlphaTheta player reads, old and new, which is why this site recommends it. The limit that matters is 4GB per FILE, not per drive, and no DJ track approaches that. Others exist, a 2TB volume ceiling and the per-model file and folder counts AlphaTheta publishes in support article 4406512510105, but a gig drive does not reach them.

A newer file system. Officially supported on CDJ-3000, CDJ-3000X, CDJ-1500X, XDJ-RX3, XDJ-XZ, XDJ-AZ, XDJ-AN, OPUS-QUAD and OMNIS-DUO, refused by every CDJ-2000 including the NXS2. Most drives over 32GB ship with it from the factory, which is why a brand-new stick can fail on an older player out of the box. rekordbox writes exFAT to USB drives and SD cards alike; HFS+ is the one file system it writes to USB only.

A Windows file system. No player reads it, and rekordbox will not export to it. If a drive is NTFS, it gets reformatted before it ever sees a booth.

One of two ways a drive describes its own layout, and the one players expect. AlphaTheta documents that the CDJ-3000 does not support the GUID scheme, so when a format tool asks, pick MBR. On a Mac this means erasing the DEVICE, not the volume, in Disk Utility.

The other layout scheme, and a recurring cause of "it formatted fine but the player refuses it". You get GPT by accident on a Mac when you erase the volume instead of the device.

Quick format rebuilds the drive’s index and is fine on a healthy drive. A full format works the whole drive, not just the index, which makes it a stress test: it is what you run on a SUSPECT drive, and a drive that fails one is retired, not trusted with a gig.

The drive nearly every gig runs on, and the one piece of equipment you actually control in someone else’s booth. FAT32 with an MBR scheme, and almost nothing surprises you. Capacity is not the thing to optimise: a drive that fails a full format is retired, and two identical smaller drives beat one big one, because the second is what saves the gig.

A second slot on some players and missing entirely on others: the CDJ-3000X has no SD slot at all, which strands a workflow built on cards. The limit that matters where the slot exists comes from the player, not from rekordbox: rekordbox writes FAT32 and exFAT to a card exactly as it does to a USB drive, but the CDJ-3000 caps its SD slot at 32 GB, which in practice means a FAT32 card.

A drive with no moving parts. As an external USB drive it is the sturdier thing to carry into a booth, because there is nothing inside to be disturbed by bass or by a knock. The catch is not speed, it is power and protocol: a bus-powered drive asks more of a player’s USB port than a stick does, and see UASP below.

The older kind, with a platter spinning and a head moving inside while it runs. It works, but it is the wrong body for a booth: physically vulnerable exactly when it is in use, thirstier on bus power than a stick, and one knock at the wrong moment is a different class of problem from a dropped USB. If a large library has to travel, put it on an SSD.

The faster protocol modern USB drives use to talk to the device they are plugged into. Worth knowing because AlphaTheta documented it as a genuine fault, not a theory: UASP-compatible drives were not recognized at all on the DJM-A9 before firmware 1.07, or on the DJM-V10 before 1.16. A drive that works everywhere and gets refused by one desk can be this, rather than the drive.

The network that connects players and mixer. Over LINK, any player can browse and load from a drive that is physically in another player, officially supported since the CDJ-900/2000 generation. If your drive dies mid-set, the drive in the other deck is still reachable.

The button you hold before pulling a drive. The manual is blunt: removing a drive (or cutting power) while the USB indicator is blinking can delete management data or make the drive unreadable. Every time, both directions: player and rekordbox.

Official AlphaTheta behaviour, and officially named: the player automatically plays a Beat Loop if it cannot start the next track when the end of the current one is reached, instead of going silent. If nothing was loaded, it is doing its job; load something. If your next track WAS ready and it still fired, the player could not read it: treat the drive as suspect.

Error meaning the track data on the drive cannot be read correctly. AlphaTheta documents it on the CDJ-3000, CDJ-3000X, XDJ-RX3, XDJ-AZ, XDJ-XZ, OPUS-QUAD and OMNIS-DUO. On the older CDJ-2000 the same number means something else: that player’s own Operating Instructions give E-8301, E-8302 and E-8303 all as PLAYER ERROR. The official response: try the track on another player, and re-import the file to the drive if possible. Usually a corrupt export or wrong file system, not dead hardware.

Error meaning the player cannot decode the file that was loaded. AlphaTheta document it together with E-8305, in one row with one cause and one action, on the CDJ-3000, CDJ-3000X, XDJ-RX3, XDJ-AZ, XDJ-XZ, OPUS-QUAD and OMNIS-DUO. The file type is the problem, not the drive, so formatting fixes nothing here. The CDJ-3000X service manual separates the two codes at engineering level and records this one as a decoding error, which does not change what you do about it.

The twin of E-8304, printed as the same message, documented in the same row with the same cause and the same action. On the CDJ-3000X the service manual records it as a format that is not supported, and there is no separate procedure for it. Treat both codes as one condition: the deck cannot read that file type, and your drive is not what failed.

The mode where a player becomes a controller for software on a laptop instead of playing from its own drive. A booth surprise on older players: not all of them support it for every software.

The player’s own software, and part of your rig whether you like it or not. Known freezes and dropouts have official fixed-in versions; check the version in UTILITY at soundcheck. And never update anything, yours or the booth’s, on gig day.

A way into a booth without carrying a drive at all. The CDJ-3000X carries an NFC touchpoint on its front panel: hold a phone running rekordbox for iOS or Android over the reader and it pulls up your online music. The CDJ-1500X supports the same login, by NFC or by QR code. It signs you in, it is not a way to play audio off the handset, and what arrives afterwards is your cloud library over the venue’s network.

Two names for the same top-of-strip knob: how loud the source arrives in the channel, before the fader. First suspect when one channel is quiet with the fader up.

The band knobs on each channel strip: three on most desks, four on the DJM-V10 and DJM-V5, which split the middle in two. The part worth knowing is what the bottom of the travel actually does, because it is not always silence. On the DJM-900NXS2 the published floor in EQ mode is -26 dB, a deep cut with the track still alive underneath it. If you reach for a full kill and the kick is still there, the desk is doing exactly what it is documented to do.

One name, two different pieces of gear, and which one you are standing at decides how the knobs behave. On the DJM-900NXS2 it is a mode: an EQ CURVE (ISOLATOR, EQ) switch on the panel, the same three knobs acting as tone controls in one position and as an isolator in the other. On the DJM-V10 it is separate hardware, a three-band master isolator sitting across the whole mix with its own crossover points. Either way, that setting is not yours. It is however the last DJ or the tech left it, and the first place you find out is the first cut you make in front of a full room.

The per-channel switch (A / THRU / B) deciding whether the crossfader controls that channel. Assigned to the wrong side, the channel is silent with every fader up: a classic silent-channel cause. Some mixers have no crossfader at all (DJM-V10-LF, DJM-V5); on those every channel behaves as THRU.

The DJ’s word and the tech’s word for the same thing: listening to a channel in your headphones before it reaches the room. If your headphones are silent, check the MIX knob is toward CUE, not MASTER, before blaming the jack.

The mixer’s second output, feeding the DJ’s own monitors, separate from MASTER which feeds the room. Two knobs, two destinations. In a pinch the booth output pair can substitute for a dead master pair.

A second EQ, on the booth output only, on the desks that carry one: the DJM-V10 and the DJM-V5 among them. It shapes what you hear in your monitors and touches nothing the room hears. Worth a look before you decide a system is broken, because a booth low left dumped by whoever played before you makes the monitor sound thin and lifeless while the floor is completely fine.

A patch point on the back of some mixers where an outboard processor sits in the master signal. If something is plugged in and nothing sends audio back, the master goes silent with every fader up. If you find one patched, it is almost certainly the venue’s: ask before pulling it.

The ordered path audio takes after your mixer: house processor, amplifiers, speakers. Past the booth output it belongs to the venue, and the fastest fix is the exact sentence: "Mixer master is up, master meters are moving. Nothing after the booth output."

Some desks take wireless audio from a phone or laptop directly, the DJM-A9 among them. Useful for a handover, or for keeping the room alive between sets. It is not a performance path: latency and connection stability make it a convenience input, not a deck to mix on. Not to be confused with NFC login on the newer players, which signs you into a cloud library rather than sending any audio.

The two translations every sound in a booth goes through. A/D turns an analogue signal into numbers, D/A turns numbers back into something a speaker can move air with. Mixer spec sheets advertise these, usually as a bit depth like 32-bit, because the conversion is where a desk either preserves the recording or quietly flattens it. Nothing you operate, and nothing you can fix in the booth, but it is the honest answer to why two mixers playing the same file do not sound identical.

The hardware doing that conversion. On a laptop setup it is a separate box or one built into the controller. On a professional DJM it is built into the mixer, which is why a laptop can plug straight into the desk over USB and needs nothing else in between. When someone says the mixer "is" the soundcard, this is what they mean.

Playing digital files from a laptop while controlling them with real turntables or CDJs, using timecode: a special record or CD carrying a control signal rather than music. The mixer reads that signal through its own soundcard and the laptop follows it. It is why a DVS setup cares so much about the phono inputs and the USB connection to the computer, and why a wrong input selector kills it instantly.

The single most useful thing in this group. A mixer channel expects either a turntable (phono, a very quiet signal that needs extra amplification) or anything else (line: CDJs, laptops, players). Feed a line source into a phono input and it distorts horribly. Feed a turntable into a line input and it is almost silent. If a channel is dead or sounds wrong with every fader up, check this selector before you blame the cable.

The two-plug pair, usually red and white, that carries stereo between most DJ equipment: player to mixer, mixer to amplifier. Unbalanced, so it does not like long runs, but it is what nearly every booth is wired with. Red is right, white or black is left. A single dead channel with a working fader is very often just this plug not fully seated.

The trap in this group: a coaxial digital output uses the same connector as an RCA plug and carries something completely different. It is a single cable of DIGITAL audio, found on some mixers as DIGITAL OUT, and it will not work plugged into an ordinary analogue RCA input. If a connection looks like a normal phono lead and produces nothing but noise or silence, check whether one end of it is digital.

The big headphone plug, and the connector for booth outputs and many balanced connections. Comes in two shapes that look nearly identical: TRS has two black rings and carries stereo or a balanced signal, TS has one ring and carries a single unbalanced channel. Plugging TS where TRS is expected is a quiet way to lose half your audio.

The small version, on phones, laptops and consumer headphones. Common in a booth only as an adapter, and adapters are exactly where handovers go wrong. If a phone has to reach the mixer, know before doors whether that adapter exists and where it is.

The three-pin locking connector, balanced, used for the mixer’s master output to the house system and for microphones. Balanced means it rejects interference over long cable runs, which is why the room is fed with it and your booth is not. Many DJs, especially outside the English-speaking world, call it a Canon: same connector, older brand name.

Why two kinds of cable exist at all. A balanced connection (XLR, TRS jack) carries the signal twice, inverted, so noise picked up along the way cancels itself at the other end. Unbalanced (RCA, TS jack) does not, so it collects hum and interference over distance. Short runs inside the booth, unbalanced is fine. Anything crossing a stage should be balanced.

The chunky twist-lock speaker connector. Worth knowing precisely because you will NOT find it on DJ equipment: it lives between amplifiers and speakers, which is the venue’s side of the signal chain. If you are looking at Speakon, you are past the booth output and past where your responsibility ends.

The small screw post on a mixer for a turntable’s thin ground wire. Unconnected, a turntable channel hums audibly. If a deck is buzzing on a vinyl setup and the fader is doing nothing about it, this is the first thing to look at.

The standard three-pin kettle lead every player and mixer takes. Unglamorous and the most common cause of a unit that "will not turn on". They work loose in a rack, and venues borrow them. A spare in the bag costs almost nothing and has saved plenty of sets.

How players and mixer talk to each other over PRO DJ LINK, and how a laptop joins that network. Ordinary network cable, nothing special about it. If LINK is refusing to connect and the settings look right, the cable and the port are worth ruling out before the settings.

Three different shapes doing different jobs on the same desk. USB-A is the flat one your drive plugs into. USB-B is the squarer one that connects a mixer to a computer for DVS or recording. USB-C appears on newer players for both storage and computer connection. The CDJ-3000X, for instance, carries one USB-A and two USB-C and no SD slot at all.