Level Meters

When I say ‘clip’, Cubase doesn’t actually clip the signal during processing: its 32- or 64-bit engine can accommodate much higher levels. But when you bounce any processing down to 24-bit (or maybe 16-bit) files, or when the signal passes through any A-D or D-A conversion stages (if you’re using external effects, for example), the audio file can’t store all that information — and you’ll end up with clipping. It’s this I have in mind when talking about clipping in this article.

In Cubase 5, the channel level-meters are digital peak meters: they show you how near to clipping the highest peaks of each track are, and if they clip, there’s a ‘virtual-LED’ indicator at the bottom of the meter that will remain red — an indication that you should pull things back a bit. They’re tweakable to some extent, as I’ll explain later, and setting them up so you know what they’re telling you is important.

But however you calibrate them, such meters tell you very little about how ‘loud’ things are. Even the briefest, inaudible transient can clip without you really noticing, and it may be that the average level is actually quite low. In other words, you could have two channels, both with the same meter reading, but one much louder than the other; or one signal only reaching -20dBFS and the other reaching 0dBFS, but the -20 one actually sounding louder! To monitor loudness, you need a different sort of meter that works on average levels — a VU or PPM meter. Cubase doesn’t include such meters, but it’s easy enough to add third-party plug-ins to do the job (I’ll discuss a few options later).

You also need to know where any meter is taking its reading from: is it at the channel input, before all the insert slots, after the inserts, or after the fader? It makes a huge difference!

A final thing to say about peak meters in general is that they’re quite a blunt tool and won’t always tell you if a signal is going to clip. It’s perfectly possible for there to be material that doesn’t register as clipping on a conventional peak meter, yet will distort when run through a D-A converter, as the converter ‘draws’ the the peak of the curve represented by the digital audio signal.

In this article, I’m going to run through a few strategies for getting the best out of Cubase’s built-in level meters, and will recommend a few free or inexpensive plug-ins that can help you plug the gaps where Cubase falls short.

Conventionally, with an analogue mixer, you’d monitor the channel inputs, to make sure the signal wasn’t clipping on the way in, and set each processor so that the signal was at roughly unity gain. That way, you could patch things in and out without affecting the level, and would hear (or see on the group meters) if you were overcooking things: you wouldn’t really need post-fader channel metering. The stereo-bus meter, though, would be set to post-fader, so you could see what was going out of the desk.

It’s a sensible approach to follow in Cubase, though I do find things slightly different in any modern DAW. For one thing, you probably can’t see all your channel and bus meters at once — so it makes sense to display the channel levels post-panner or post-fader when mixing. That way, you know you’re not overcooking things with processing before the signal goes to the fader, or from the fader to the bus. On the master bus, group or effects channels, I’ll also want to know whether the signal is clipping on the way in, and will often rely on a dedicated meter on the last insert on the stereo bus to monitor the output level.

This isn’t just an aesthetic option. For example, if you leave the ‘turnover points’ spaced apart, the transition between colours is quite gradual, getting redder (using the default colour scheme) as the signal gets hotter. If, instead, you pull them close together into pairs you can get a much clearer indication of when a certain (non-peak) level has been reached. It’s far from conventional, but I find that latter approach handy, because I can calibrate things so that I can easily set up individual drum tracks to peak no higher than around -12dB post-fader, without having to look at the numeric values on each track. That way, I can be more confident that I’m leaving sufficient headroom on the drum bus, without having to scroll along a busy mixer and look at the bus itself.

The unity-gain approach discussed earlier is a good practice to get into, but it’s not the only way of working. Some manufacturers offer an input and output meter as standard on their plug-ins, and these can help you to get a cleaner, more satisfactory result from your processing: the bottom line is that you shouldn’t really be ‘clipping’ at any stage, because whereas analogue gear might distort in a muscially pleasing way, and while analogue-modelling plug-ins can imitate this behaviour, real digital clipping (unless used as a deliberate effect) will offend your ears.

If your plug-ins don’t include the necessary meters, try inserting Cubase’s Compressor with the threshold set to maximum (so that it doesn’t act on the audio), and use its meter: simply drag it around your project to the appropriate insert slot when you want to check levels.

When it comes to inter-sample distortion, SSL offer another freeware meter called X-ISM (www.solid-state-logic.com/music/x-ism/index.asp), which simulates the process performed by a D-A converter, and warns when the recreated analogue signal would go above 0dBFS, even though the digital peak-meter would tell you that the signal remained within that limit.

There are many commercial offerings you could look at if you feel the need, from the likes of RNDigital and Waves, for example, but it’s also worth looking at the range of other plug-ins you already own: some of them include quite sophisticated metering options. For example, I use Universal Audio’s Precision Limiter as often for metering as for its intended function as a limiter.

Nonetheless, you may sometimes find that your mix is clipping at the bus-input stage, and Cubase gives you a few options for handling this. First, you could reduce the level of all the channels feeding the bus — but, whichever way you choose to do this, it’s a faff once you’ve started to use automation, or threshold-sensitive processing on groups or effects channels. Alternatively, you can use the input trim control at the top of the bus to attenuate the signal before any processing. Given the floating-point processing, that’s a perfectly acceptable approach — though unecessary if you get the levels right in the first place! Finally, you can use the input gain of the first insert plug-in on the bus to attenuate the signal, which is essentially the same thing. Also, don’t forget the advice I’ve already given about monitoring the input and output levels of your insert plug-ins, because this applies as much to your master-bus plug-ins as it does to any others.

Meters can only help you so much, and there’s really no substitute for using your ears — but the meters in Cubase are there for a reason, and it pays to understand what they and any other meters are telling you: not only can they help you avoid the undesirable sound of digital clipping, but they really can help you to create a better mix of any track.  0