Mixers and CD decks for DJing
Checking CD decks
How the pitch control affects the playback speed on CD decks is harder to check than on a turntable, as you don’t have a visual reference of the strobe light that is on a turntable. However, CD decks don’t usually have the same motor problems as turntables, so all that needs to be checked is that the pitch control and pitch bend functions work properly and are clean.
Tips for checking out CD decks
Ensure the pitch control increases and decreases the speed of the tune in a constant and smooth way and that the pitch bend buttons change the pitch temporarily when you press them, and the pitch of the tune returns quickly to the set pitch when the buttons are released.
- Try to use every function on the CD unit. If you've done your research then you will know what functions to expect so take a checklist for that specific model and make sure that all the functions work.
- Inspect the CD loading system. If the CD deck loads with a tray, make sure that there is no damage and the CD loads smoothly in and out. If the CD slots directly into the deck, then insert a CD a few times to make sure that it isn't spat back out. If the CD deck uses a top-loading method, make sure that the deck closes properly, and as with the other loading methods ensure that the CD plays properly when loaded.
- If the CD deck has a good antiskip function (which stops the CD from skipping because of vibrations), get a working demonstration of that. Make sure that you’re satisfied with the antiskip, and that it does actually prevent the CD from skipping due to vibrations.
Always get a chance to see the mixer turned and in action and that is works correctly. Before you play anything through the mixer, connect the turntables/CD decks to the mixer and listen. If you can hear an electrical hum from the equipment or through the speakers, turn off the decks so only the mixer is on. If you can still hear a loud hum, check the connections (in particular, the earth connection) for any problems. The noise could be a harmless operational hum given off by the mixer, but if you are not convinced that this sound’s good, then it probably isn’t harmless.
After you’ve listened to the mixer with nothing playing through it, put on a record/CD and check that every control does what they’re supposed to. The master level, the gain control, the EQs, the channel faders, the cross fader, the booth controls and effects section, everything needs to be checked for each channel on the mixer. Listen for any signal dropout or crackling sounds as you turn knobs and move faders.
Pay particular attention to the cross-fader when checking the faders. The cross-fader should have a smooth fluid motion from one side to the other, and you need to check for faults in the fader’s control of the audio. The first thing to listen for is crackling as the fader is moved from one side to the other, but also listen for any music coming in from the other channel. If you’re playing music into channel 1, and nothing is playing on channel 2, move the cross-fader over to channel 2, where it should be silent. If you can still hear channel 1 playing faintly when you should have silence then there is a problem with the cross-fader.
A worn cross-fader may be a sign of wear and tear to the mixer, but it may just be worn down after constant use by a scratch DJ so go with your instincts. If you have headphones and a microphone available, try them with the mixer. Move the cables of the headphones and microphone about while they are plugged in and listen for any loose connections causing the signal to cut out.
Use every headphone cue control, making sure that a good, clear sound from each channel is achieved, and if the headphone section includes a headphone mix or split cue, test them to ensure that the signal doesn't cut out. Plug in the microphone and check that the controls and the inputs do not have any crackling and if the mixer has a talk-over function, which dips the volume of the music so you can be heard talking over it, then make sure it also works.
For mixer outputs you’ll probably see a Master Out, a Record Out and, possibly a Booth Out or Zone Out if it is a good mixer. Test all of the outputs through the amplifier, and make sure that no breaks occur in the signal when the wires are moved about.
Don’t overlook the Line/Phono switches when checking out a second-hand mixer. Ensure that the switch from Line to Phono for every channel works without crackling, and check for silence when you switch to either Line or Phono when they don’t have an input. For example, if you have turntables plugged into the mixer, when you switch to Line, make sure that you can’t still hear the turntable playing.
If the mixer has any of the other features like BPM counters, cross-fader curve adjusts, punch buttons or hamster switches, ensure that these are all checked and work correctly too.
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