A controller packs decks, a mixer and often a sound card into one box, which makes it the most practical way into DJing and one of the easiest things to buy used, as long as you test it with the software you plan to run. The questions that matter are partly physical (jogs, pads, faders) and partly about software: what the hardware unlocks, whether it needs a laptop at all, and whether its driver still works on your computer.
The models
- Numark Mixtrack Platinum FX: a four-deck controller with 6-inch capacitive-touch jog wheels that have colour displays showing BPM, platter position, time remaining, pitch and key. It has eight pads per deck and six effects with paddle triggers. It is powered from the computer's USB port and is not standalone: it needs Serato DJ Lite running on a Mac or PC.
- Numark NS6II: a four-channel controller with 6-inch jog wheels, a 2-inch colour display in each, touch-capacitive knobs, RGB pads and two USB ports for handovers between DJs. Its mixer works standalone, with two phono/line inputs and two mic inputs.
- Numark NS7III: 7-inch motorised direct-drive platters with real vinyl and felt slipmats, a high/low torque switch, three 4.3-inch colour screens and 16 velocity-sensitive pads. Its four-channel mixer works with or without a computer; channels 1 and 2 take phono or line, and channels 3 and 4 are line only.
- Numark Mixstream Pro: a standalone unit running Engine DJ, with a 7-inch touch screen, 6-inch capacitive jog wheels, built-in speakers, Wi-Fi streaming, two USB inputs and an SD slot.
- Pioneer XDJ-RX2 and XDJ-RX3: two-channel all-in-ones that play rekordbox-prepared USB sticks without a laptop. The RX2 has a 7-inch touch screen; the RX3 has a 10.1-inch screen, jog displays, a Jog Adjust control and three USB ports.
Jog wheels
On capacitive-touch jogs (Mixtrack Platinum FX, NS6II, Mixstream Pro), touching the top plate should stop or scratch the track, and touching only the edge should bend the pitch. Test both, with clean, dry hands, and watch for touch that drops out or triggers on its own. Spin each wheel and listen for scraping, and check for wobble or play in the shaft. The jog displays on the Mixtrack Platinum FX, NS6II and XDJ-RX3 should be bright and fully lit.
The NS7III needs more attention because its platters are motorised. Let both platters run for several minutes. They should turn at a steady speed without noise, and the speed shouldn't drift. Hold the record to stop it, then let go: it should pick up cleanly. Flip the torque switch between high and low and feel the resistance change. Check both vinyl discs and slipmats are included.
Pads, buttons and encoders
Press every pad in every mode the software offers: hot cue, loop, sampler, slicer. Look for dead pads, pads that double-trigger and RGB lights with a missing colour. On the NS7III the pads are velocity-sensitive, so check soft and hard hits register differently. Press every transport button, turn and push every encoder (browse, loop, beat jump), and on the Mixtrack Platinum FX pull each effect paddle in both directions.
Faders and knobs
Controller faders usually send data rather than audio, so a worn one shows up as jumping values on screen rather than crackle. Watch the software as you move each fader slowly: the on-screen value should follow smoothly with no jumps. Do the same with the pitch faders, the crossfader and every knob. On the NS6II and NS7III, whose mixers also pass audio standalone, test the analogue inputs too: connect a turntable or player to the phono/line inputs and listen for crackle as you move the channel faders and EQs. Touch-capacitive knobs (NS6II, NS7III) should trigger their on-screen action when touched.
Software and licences
This is where used-controller listings mislead most often.
- Serato says the Mixtrack Platinum FX unlocks Serato DJ Lite for free. Serato DJ Pro is a paid upgrade.
- Serato says the NS6II, NS7III and XDJ-RX3 unlock Serato DJ Pro for free when plugged in.
- Serato's DJ Pro page says that if you have hardware that unlocks DJ Pro when connected, you don't need a licence or subscription. The unlock happens when the unit is connected, so it isn't something the seller has to hand over separately.
- A paid Serato DJ Pro licence or subscription that a seller bought for a Lite controller is different. It belongs to their Serato account and isn't part of the hardware. If a listing says a Mixtrack "comes with Serato DJ Pro", assume you will need your own unless the seller can explain how they will hand it over.
- Pioneer says the XDJ-RX3 is a hardware-unlock device for rekordbox's Performance mode and also controls Serato DJ Pro. Pioneer's XDJ-RX2 page describes rekordbox features unlocking when you connect a computer.
- The Mixstream Pro runs Engine DJ on board. Its library comes from the Engine DJ desktop software, which can import from iTunes, Serato DJ, rekordbox and Traktor.
Driver and OS support
Before you buy, check the maker's support page for your exact operating system version. AlphaTheta's macOS Tahoe 26 compatibility page lists the XDJ-RX2 and XDJ-RX3. For Numark controllers, check Numark's support pages and Serato's hardware page for the model. Discontinued controllers lose support over time; the rekordbox FAQ, for example, names several older DDJ controllers and the XDJ-R1 as no longer supported. Then, when you test, use the same software version you intend to use, not whatever the seller has installed.
Standalone or laptop?
This is the biggest practical difference between these units.
- Laptop required: Mixtrack Platinum FX.
- Laptop for decks, mixer works without one: NS6II and NS7III. Without a computer you can mix external players or turntables, but the jogs and pads have nothing to control.
- Fully standalone: Mixstream Pro (Engine DJ from USB, SD or streaming), XDJ-RX2 and XDJ-RX3 (rekordbox-exported USB sticks).
If you want to play without a laptop, test standalone playback from your own stick prepared in the current software. For the XDJ-RX3, the rekordbox FAQ lists it among the units that read exFAT sticks.
Power supply
The Mixtrack Platinum FX runs on USB bus power, so a weak USB port or a long, thin cable can cause disconnects; test it on your own computer. The Mixstream Pro uses a 12 V, 3 A centre-positive DC adapter. A substitute adapter must match the voltage and polarity and supply at least that current. For the NS6II, NS7III and XDJ units, check the correct power cable or supply is included and that the socket holds the plug firmly. Ask whether the adapter is the original. An unbranded supply with the wrong rating can cause odd, intermittent faults.
Test routine
- Power up from the supply you will use and check every light and screen.
- Connect your laptop, open your software and confirm it recognises the unit (and unlocks what it should).
- Test every jog, pad, button, knob and fader, watching the software.
- Play audio through master and headphones; test the mic and external inputs.
- For standalone units, play from your own USB stick or SD card.
Thinking about separate decks and a mixer instead? Read buying a used CDJ and buying a used DJ mixer.
