Vinyl Control

What is it?

Vinyl control allows a user to manipulate the playback of a song in Mixxx using a turntable as an interface. In effect, it simulates the sound and feel of having your MP3 collection on vinyl.

How does it work?

Vinyl control uses special timecoded records which are placed on real turntables. The audio output of the turntables is plugged into a computer, on which Mixxx is running. When a record is played on one of the attached turntables, Mixxx decodes the timecode off the record, and uses information from that to manipulate whatever song is loaded.

For those more technically inclined, Mixxx uses Scratchlib to decode the FinalScratch timecode and xwax to decode the Serato/Traktor timecodes.

What do I need to use it?

It's possible to use Mixxx's vinyl control with several hardware setups, but the basic ones are:

Setup 1: Vinyl DJ Two timecoded records, two turntables with phono preamps (or line-out), and two "sound inputs". You can skip the phono amplifiers if you use the snazzy new software preamp in Mixxx, though this will not provide as clean a signal and may not work for everyone - line-level signals are preferred.

Setup 2: CDJ Two timecoded CDs, two CD decks, and two "sound inputs".

Now, for the "sound inputs", you have two options: You can either use a fancy DJ soundcard that has multiple stereo line-inputs on it, or can use two soundcards (each with a single stereo line-in). Currently, Mixxx's vinyl control has only been tested with the latter configuration.

For best scratch performance with vinyl control, your system must be able to handle setting the latency to 10ms or less otherwise the scratch sound will start to become distorted as latencies (and lag time) increase.

For timecoded records or CDs, you can use any of the records supported by Mixxx:

Timecode Support


Vinyl	Responsiveness
Serato CV02	Very high
Serato CD	Very high
Traktor Scratch	Very high
FinalScratch (Standard)	Moderate
FinalScratch (Scratch)	High
MixVibes DVS CD	Untested
MixVibes DVS Vinyl	Does not work

At the present time, Serato records are the ones you should purchase if you're looking to buy vinyl. If you want to use CDs, you can download a free copy from Rane here. (Information is on this page.)

Support for Final Scratch records needs work, and at the moment isn't nearly as good as the Serato/Traktor support.

How responsive is it? Does it have absolute mode?

The responsiveness of Serato/Traktor records is limited only by the latency of your soundcard. This latency can be adjusted in Mixxx's preferences under the "Sound Hardware" pane. With a good soundcard which is properly configured and a fast CPU, latencies below 10 ms are possible.

Mixxx supports absolute and relative mode with all of the vinyl listed in the table above.

What does it look like in action?

Check out these videos (YouTube):

(Need more YouTube videos here, and a screenshot of the prefs dialog)

Troubleshooting

The downside to vinyl control is that it adds an extra layer of complexity to troubleshooting - Now there's a pair of turntables to worry about in addition to software problems.

To begin troubleshooting any problems you have, please do the following:

Make sure your needles are clean and your records are relatively dust-free. (Dirty needs will cause Mixxx to playback irregularly.)
Make sure your left and right RCA cables are plugged into the correct plugs. A swapped pair of RCA cables will cause Mixxx to also behave strangely, such as play songs in reverse.
Make sure your tonearm is balanced.
Make sure your soundcards have stereo line-in. Many on-board soundcards only have mono line-in and won't function correctly with vinyl control. Before you buy any soundcard, verify that it has stereo line-in on it.
Make sure the recording volume is turned up in your soundcard's volume mixer. Too quiet of a signal can result in pitch control being inverted.
Make sure you don't have 50/60 Hz ground-loop hum. Ground your turntables to your amp/mixer. Ground-loop hum can cause choppy playback and otherwise unpredictable behaviour.

Next, verify that the signal is being received by your computer properly.

Windows: Fire up "Sound Recorder" from Start->Programs->Accessories->Entertainment, then follow the instructions below.

Click record and hit play on your turntable. After a few seconds, stop Sound Recorder and your turntable. Playback the sound that was just recorded. If you hear a relatively stable tone, your soundcard is probably capturing the timecode signal correctly. If you don't hear a tone, check your recording volume mixer and capture settings. Also, check that your turntable is plugged into the correct plug on your soundcard.

Linux: Grab a copy of xwax, then follow the instructions below. (If you want to use a sound editor like Audacity, follow the Windows instructions above.)

Start xwax with the -t option set for the type of timecode vinyl/cd you're using, -l for the path to your music files, and -d for the sound device your deck is hooked to. (E.g. xwax -t serato_cd -l ~/MusicFiles/ -d /dev/dsp ) More info. Now just start your record/CD and watch the timecode scope (crosshairs) in the upper right corner. You should see a healthy double-circle display. Adjust the input levels using a mixer control for the device (eg. alsamixer). When settled, the circle should approximately fill the timecode scope display but not be cut off. (If you don't see anything, check the mixer program to be sure the Line input is selected/enabled and turned up.)

For both: The last step to try is to launch Mixxx, and go into the "Vinyl Control" pane in the preferences dialog. Select the soundcard with the turntable attached to it under "Deck 1", and select the timecode you're using. Click OK, then in the menu bar at the top, select "Options->Enable vinyl control". Load a track into Mixxx's top player (Player 1) and hit play on your turntable. Mixxx should begin playing the track in Player 1.

How can I help?

If you're interested in adding support for more timecode records, your effort is best spent contributing to xwax. Any additional timecode support added to xwax will be included in Mixxx. If you're interested in fixing some of the quirks that happen or adding extra features to the vinyl control support in Mixxx, email Albert and he can help you get started working Mixxx's vinyl control code.