PERFORMER NOTES

MW Limiter and Quan Jr

Published in SOS May 2002
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Technique : Digital Performer Notes

We continue our examination of DP3's Step Record window, and come over all of a dither with MW Limiter and Quan Jr. Plus all the latest MOTU-related news.


Robin Bigwood

Last month we covered the basics of DP3's Step Record window, and looked particularly at how many of its features can be operated using keyboard shortcuts rather than mouse clicks. One feature that isn't covered by a shortcut, though, is Transport Lock, which is activated by highlighting the padlock icon in the title bar of the Step Record window, and is activated by default whenever the window is first opened. This keeps the main transport in sync with the 'Current Step' location (displayed at the bottom of the window), so that as you enter notes, the rest of your sequence plays along in time,

  Current Versions *  
  Digital Performer v3.02.  
pausing when necessary. If you enter a new Current Step location, the main transport jumps to it as well.

Doing almost anything other than step entry -- like playing or rewinding -- causes Transport Lock to be deselected. If you're not expecting that, it's all too easy to inadvertently enter some notes in the wrong place. But deliberately deselecting the Lock has its uses too. The main one is being able to record in step time whilst a sequence is playing -- a great technique for entering complex rhythmic parts into a section being looped by the Memory Cycle function. To do this, you just set up Memory Cycle, hit Play, and then open the Step Record window -- it opens with Transport Lock deselected, and you can begin entering notes whenever you wish. If you need to switch MIDI tracks, you don't have to stop the sequence -- just select another track from the 'Recording On' pop-up menu. Additionally, you can solo the 'Recording On' track at any time by clicking the Solo Playback box (or hitting 'P' on your keyboard).

Duration

By default, the Step Record window uses the maximum duration (in ticks) for selected note values, so entering a quarter note (crotchet), for example, results in a MIDI note 480 ticks long. This is certainly logical, but leads to parts that can sound unnaturally smooth and sustained. To avoid this, or to easily enter detached or staccato notes, try typing a number less than 100 (percent) in the duration field. Typing '50', for example, gives rise to notes that are only half the selected length, but the current step location still moves on by the full amount.

If you find yourself always entering notes with durations shorter than 100 percent, you can set alternative default durations. Simply double-click on one of the nine rhythmic value buttons in the Step Record window to open a little dialogue box in which default duration can be specified in percentage or 'raw tick' terms (see screenshot, above left).

For maximum control, though, go to the Step Record window's mini-menu and se

  Quick Tips  
  When the Step Record window is open, the keypad is disabled, meaning that the 'dot trick', normally used to locate to specific positions on the time ruler, won't work. Hold down the Apple key and hit 'T' instead to directly enter a location into the main transport.

When you open the Step Record window, you always locate to where the main Song pointer is. So set your position with the transport before opening the window, to save having to type in a step location.

 
lect 'Note Durations'. Here you can set a duration range (in percentage terms) and have successive notes randomised within it. This often gives more natural-sounding results when set to a range between 60 and 80 percent. Even better, though, you can tie duration value to a MIDI controller such as a modulation wheel on a synth. Just click inside the 'MIDI Remote Control' field and waggle the mod wheel (or other controller source). DP 'learns' the source, and you can specify upper and lower values for it (nearly always 0 to 127). If you now return to the Step Record window, you'll find that duration value is remotely controlled by the modulation wheel. Step Record's offset amount -- the extent to which entered notes play ahead of (negative numbers) or behind the beat (positive numbers) -- can also be controlled in this way. The ideal MIDI remote controller in this case is the pitch-bend wheel, as it can produce both positive and negative values.

The Small Print

Step Record can be used to enter MIDI data other than notes -- you can use it to accurately place a patch-change message, for example. In this case, use the Current Step field to get to your desired point in the sequence, send the patch-change message and then hit Step (Enter on the keypad). This works for all sorts of MIDI data, and if you find yourself entering much data this way, you might find it worth switching on Step Record's Click Mode, which produces a speaker click to confirm that a MIDI event has been entered. You turn it on (or off) by clicking the speaker icon on the title bar in the Step Record window.

Dithering With Quan Jr & MW Limiter

I promised more on MW Limiter's dither options last month. Many people are unaware of the potential importance of dither, particularly when you're using an application capable of recording at 24-bit resolution.

DP3 can of course handle digital audio at various bit depths, and many users these days will record a project at 24-bit resolution, and then need to master it at 16-bit for distribution on conventional Red Book audio CDs. Bit-depth reduction is nearly always carried out by quantising the value of each 24-bit digital 'word' into 16 bits, and then adding a bit of dither -- which is just another name for noise which masks the distortion and digital artifacts that result from the quantisation process.

There are several ways to change bit depth and/or add dither in DP3, so here's a quick guide:

PRODUCING A 16-BIT MASTER FROM A 24-BIT PROJECT

For this you should set up a Master Fader (or Aux) which handles all the audio from your project, and put the Quan Jr or MW Limiter plug-ins on it (Quan Jr has exactly the same dither options and algorithm as MW Limiter, but of course if you wish to do some final limiting on your master before the bit reduction, the latter is a better choice). Enter '16' into the 'Bits' data field by typing it in or just hitting the little '16' button (see the top screenshot on the previous page), and turn Dither on. If you're mastering digitally to an external DAT (for example) you can now just play the sequence -- what emerges from your digital output is quantised and dithered to 16-bit resolution. If you're producing a file ready for burning to CD, you just need to select 'Bounce to Disk' from the Audio menu, set the resolution to 16 bits, make other settings as appropriate, and then hit 'OK'.

TRANSFERRING A 24-BIT DP3 PROJECT TO A 16- OR 20-BIT ADAT/DTRS

Here you need to put Quan Jr or MW Limiter (with dither turned on) on every channel you're transferring to the digital recorder -- otherwise the 'extra' bits are just ignored (truncated) when the digital signal reaches the recorder.

IMPORTING & CONVERTING 24-BIT FILES FOR USE IN A 16-BIT PROJECT

Import the file using the 'Add Soundbite' command in the Soundbites window's mini-menu, then, in the same window, select the Soundbite from the list, and select 'Convert Sample Format' from th

  DP3 News  
  Last month, I mentioned how the Trasher plug-in from ReFX could be used for lo-fi bit-depth reduction techniques. Well, Trasher II is now available, with more features, and it sounds great (or terrible, depending on how you look at it!). ReFX's other plug-ins -- the TBL bassline synth and the fabulously potent QuadraSID Commodore 64 sound chip emulator (pictured below) also work very reliably under Audio Ease's VST Wrapper v3, and are great value for money. Demo versions are available from: www.refx.net

PSP Audioware, whose excellent VintageWarmer plug-in is now available in MOTU-native MAS format, are gearing up to release MAS versions of their existing StereoPack and MixPack plug-in suites (pictured below). I've been using beta versions for a few weeks, and they seem very stable, so watch for an official launch soon at: www.pspaudioware.com

Incidentally, PSP's freeware Pianoverb (currently available only in VST format) also works nicely under VST Wrapper, and is well worth the few seconds of download time.

 
e same mini-menu. Select 16-bit, configure the other options as necessary, and hit 'OK'. Dither is only applied to this bit-depth reduction when the Dither option is checked in the Audio menu at the top.

Despite what the DP3 manual says, the Audio menu's 'Dither' option is only used when making bit-depth conversions from the Soundbites window, and when destructively applying plug-ins from the Audio menu (which are in 16-bit Premiere format) to 24-bit audio files -- it has no bearing whatsoever on a Bounce to Disk.

'ARTISTIC' BIT-DEPTH REDUCTION

Reducing bit depth on individual tracks or small sections of music is quite a trendy effect these days, and in DP3 Quan Jr is superb for dialling in controlled amounts of grunge. Using 10- or 12-bit resolution on a drum track (for example) can really help impart some crunchiness. Lower resolutions become increasingly nasty, and under about 3 bits, even quiet material becomes horribly loud (as more and more of the waveform is quantised to maximum amplitude). In these cases, using MW Limiter can help to save your monitors, and your hearing. For unprecedented levels of grunge (and a refreshing absence of dither noise) keep dither turned off.

Both Quan Jr and MW Limiter have a noise-shaping option, which changes the quality of dither noise in a psychoacoustically-based attempt to make it sound less intrusive. When you select this option the noise level actually increases, technically speaking -- it just sounds quieter. Obviously, if dither isn't selected in the first place, noise-shaping does nothing at all.

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