CUBASE NOTES
Integrating external hardware effects into the signal path
Technique : Cubase Notes
The VST mixer seems to acquire new features with every version of Cubase — but what order do they come in, and how can you integrate external hardware effects into the signal path?
A simplified diagram of the signal flow within the VST mixer. Audio passes first through any channel insert effects, followed by the dynamics and EQ, before being sent to any auxiliary effects and returned, via the Master mixer and insert effects, to the Master outputs.
Mark Wherry
In this month's Cubase Notes, we're going to cover a couple of subjects that can cause head-scratching for even the most experienced user. Hands up if you've ever wondered about the signal routing on the VST mixer, or if you've heard about plug-in delay compensation and think it might have something to do with getting a discount for having to wait so long for the arrival of your LM4 Mark II... These are the questions we'll be answering in this very column — aside from the discount, that is!
What Goes Where?
One aspect that attracts people to Cubase is the look and feel of the VST user interface, designed to mimic traditional studio hardware and make it easy for people to produce music. But because all of the complexity is hidden behind this glossy exterior, it's not immediately obvious how the audio is routed around the VST mixer, especially once you start activating inserts and the internal dynamics and EQs.
When audio is routed to a channel on the VST mixer, either from the Arrange window or through the monitoring facility on your ASIO card, it passes through the inserts in the top-down numbered order they appear in the VST Channel Settings window. The signal is processed by the internal dynamics (Auto Gate first, then Auto Level, Compressor, Soft Clip and finally Limit), followed by the internal EQ section. If no inserts, dynamics, or EQ are used, the signal remains untouched.
After this, if any of the sends are set to Pre (fader), the amount of signal specified is sent to the relevant destination, which will be a VST send effect, a group channel, or a physical output, before the signal is processed by the fader. Otherwise, the sends will take place after any volume adjustments made by the fader.
Sending It Outside
If you've only ever used a stereo-in/stereo-out audio card, you might not realise that if you're using a card with multiple outputs, Cubase can address these extra hardware channels and make use of them in many different ways. One thing you can do is patch in any special hardware effects you might want to use. When you select the destination for a send control, in addition to the VST effects or group channels, you also have the option to send the signal to any hardware buss you've activated in the VST Master window. Connect the relevant output from your audio card to the input on your hardware box, say a Lexicon 480, for example, and then the output of your Lexicon to one of the spare inputs on your audio card.
If you're lucky, your audio card will be able to function with a latency low enough that you can simply activate the monitoring feature on some audio channels, without actually having to record the output of the effects unit back into Cubase as an audio track. Even so, there are circumstances in which you might want to do this: so that you can send the song to other people, for instance, or revisit it yourself without having to worry about connecting up the hardware again.
Another idea is to use the send controls to create headphone mixes, which is especially useful if you don't have a separate desk, or your desk isn't quite up to the task. Simply route all the Send 5 controls, for example, to one of the activated hardware busses and then create a level mix from that, just as you would on a traditional console. All we need now is for Cubase to acquire the handy 'Copy to Sends' feature in Pro Tools, where the levels on all the volume faders can be copied to all the Send 5 (or whatever) controls on the same channels...
It's worth noting, however, that the sends on the VST Channel Settings window are mono sends, even on stereo tracks. If you want to send the left and right channels to a group channel or hardware buss, you'll need to use one send control for the left channel, and yes, you've guessed it, another send control for the right. Be careful to hold down the Alt (Mac: Option) key while you're doing this, as described in my November 2001 column, so you can set the send controls for the left and right channels independently.
Master Matters
The outputs of the audio, instrument, ReWire and group channels, along with the outputs of the send effects, get mixed (or summed) to the specified stereo busses. While it's possible to route the outputs of individual channels or send effects to a hardware output other than the master (if your audio card has multiple outputs) for the purpose of submixing on a hardware console, generally speaking, and for the purpose of this explanation, most people probably mix everything directly to the master stereo buss within Cubase.
One thing to remember when you've activated the Link Editors button is that you can only have one MIDI Editor open at a time. When you try to open a different kind of editor window, the previous one is automatically closed before the new one opens. However, it is perfectly possible for the Audio Editor to be opened alongside a MIDI Editor, so you can work with both audio and MIDI parts in Link Editors mode. A great way of working if you have more than one monitor display is to have the Arrange window on one monitor and an editor on the other. Like most dual-display working methods, you'll be amazed at how much this speeds up the composing process.
The master stereo buss is actually in itself another expedition in signal routing, which is kindly illustrated for us on the master panel, displayed either on the VST Master Mixer window or by activating the Master button on the VST Channel Mixer. First, the stereo signal passes through up to four additional insert effects, which allow you to process your entire mix within the Cubase environment. You can open the VST Master Effects rack by clicking on the Master FX button, although in reality this window is pretty redundant.
Linking Editors
It might sit there staring at you from the Arrange window's function bar all day long, but the Link Editors button is often criminally overlooked, especially by those who have more than one monitor display. When you want to edit a Part in Cubase, you simply double-click it, the editor opens, you make the changes, and then close the editor. To edit another Part, you double-click it, the editor opens, and, well, you get the idea. Activating the Link Editors button means that once an editor is open, the currently selected part is displayed in the editor, so you never have to close and reopen the editor window again.
To select a master effect, click one of the No Effect labels on the master panel itself, and a list of suitable (stereo-in, stereo-out) effects will appear, as installed on your system. Choose the effect as normal, and then activate it by clicking the small On button to the right of the label. Ctrl- (PC) or Apple-clicking the On button will open the editor window for that particular effect. You can also solo master effects in the chain, or simply bypass all four effects simultaneously for A/B comparisons. And if you come up with a mastering setup that's working quite well, you can load and save master sets by clicking on the File pop-up menu on the master panel to use the same settings as a starting point in another Song.
After the master fader, you can choose to activate Cubase's built-in dithering facility. VST/32 users get UV22, the dithering algorithm to the stars, included in their master section, and compared to the cost of a separate UV22 plug-in, it's worth paying the extra to get VST/32 for this feature alone. Something to bear in mind, though, is that the UV22 algorithm included is hard-wired to dither from VST's internal 32-bit engine to 16-bit for CD or MP3 mastering, so unless you're mastering within Cubase and dithering to 16-bit, make sure you leave the internal dither feature switched off. While the standard dithering algorithm supplied with plain VST or Score isn't of the same quality, it's actually more flexible, since you choose from a range of bit depths to dither to: 8, 16, 20 and 24.
The final stage in the signal's journey is either to end up at the hardware output specified underneath the master fader (to your speakers, DAT, or other destination), or to be processed into a file via the Export Audio button. Martin Walker covered the latter process in this very column back in the June 2001 issue, so check out your back issue collection or visit www.soundonsound.com/sos/jun01/articles/cubasenotes.htm if you want to know more.
Where Are The Dynamics?
One of the most common questions that will come to mind when you start using the VST groups or instrument channels is why neither of these feature the built-in dynamics found on audio channels. However, as is often the case in the world of DSP, a seemingly simple question has anything but a simple answer. Every DSP process, whether a simple volume fader or a complex reverb algorithm, takes a specific amount of time to do its job, and even if you have a system with the lowest latency audio card, the use of plug-ins, in particular, will always result in a small amount of added delay. However, before you start to panic, bear in mind that when we talk about plug-in latency, we're talking in samples, of which there are 44100 every second if we're recording at 44.1kHz.
On playback, Cubase knows (to a certain degree) what's going to be happen in advance, and if a plug-in is well written and declares its latency to the system, a balancing act can take place to ensure everything comes out in perfect sync. This act is called Plug-in Delay Compensation, and you'll notice it as an option in the Audio System Setup dialogue: if tracks where you're using insert effects or the inbuilt dynamics (which are an insert effect in all but name), suffer a slight delay on playback, turn on Plug-in Delay Compensation to sort it out.
To get back to the original question of why there are only dynamics on audio channels, it's because the input of a group channel, for example, can come from any number of tracks with inserts on, or sends, and so on. This means that it's currently impossible for Cubase to know exactly what's going to happen in advance. In a nutshell, there's no plug-in delay compensation on group channels.
However, if the inbuilt dynamics are essentially an insert effect, what happens when you use insert effects (such as the Dynamics plug-in) on group channels? Well, unfortunately, the same applies, and if you have a particularly greedy plug-in, such as the inbuilt Dynamics, and a less powerful computer, you might not be able to use it as an insert on a group channel because the delay will be too great. 
Perhaps the most common reason for bouncing effected tracks to hard disk is so that you can switch off plug-ins and regain CPU power. However, there's another reason why you might want to do it if, like me, you much prefer using Cubase's vector automation (Dynamic Events) to its fader automation. Any level changes created either with fader automation or Dynamic Events take place before the audio reaches the channel dynamics and insert effects: so what if you want to have audio that is compressed before being automated? If you're using the fader automation, you can simply route it to a group and automate the group fader, but if you prefer using Dynamic Events, you'll need to bounce the compressed audio to disk and import it as a new Part. Sam Inglis
Cubase Tips
When you've done some editing in one of Cubase's many editor windows, you can close it in the normal Mac or Windows way, or by simply pressing return. However, if you press Escape, any changes you've made since opening the editor can be ignored before the window is closed. Not quite unlimited undo, but still very useful. Mark Wherry
Current Version
• Mac and PC: v5.1.
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