From Home production

The Rules of Digital Audio

Digital audio is a very different beast to its analogue forefather. Cleaner, colder, trickier. The science behind it is enough to make most people’s eyes glaze over, but there are some important rules that are often broken by those who’ve not taken the time to look into it.

To save you the time, here are the fundamentals of digital audio (without the number crunching).

Levels and clipping

The most common digital mistake is inheriting the ‘run it hot’ mentality of an analogue engineer. Under no circumstances should you run a digital signal into the red. Unless you want your audio to sound edgy and horrible, which you might. (There are always exceptions).

Analogue clipping makes a pleasing distortion that if used sparingly can really enhance a sound, digital clipping is an audio error code. If any digital clipping is to occur, it should be left to the mastering engineer to make it happen. Even then, it’s fraught with controversy, and we avoid it as much as possible.

The rule of thumb when recording is to keep it clean, firmly in the green. If recording in 24 bit, hitting somewhere around -18dB on your VU meter will give you plenty of signal to work with while giving you plenty of headroom for peaks.

Sampling rates

The sampling rate for CD quality audio is 44.1khz. Therefore lots of people work at that rate. However, DVD quality is 48khz, presenting a good reason to record at the higher rate.

It is generally a good idea to record and mix at higher than CD quality as any processing you do will degrade the original fidelity of the signal to some extent. Some plugins also work better at higher sampling rates (also why many now internally upsample). The higher the rate the better, so work at the highest rate your processor can handle.

But, keep downsampling to the mastering engineer. Using sub-par converters can cause undesirable effects when converting sample rates, so if you’re not sending it out for mastering, you might be better off sticking to 44.1 all the way through. Check out http://src.infinitewave.ca/ to see where yours stack up (pictured).

Bit depth

CD quality audio works at 16bit (as does DVD) so this is definitely the end goal. However, as with sampling rates, using a higher bit depth during tracking, mixing and mastering will help preserve fidelity and often improve processing quality. There has also been talk of the introduction of 24 bit downloads so it’s a good idea to make sure you’ve got the audio to back it up – you can up the bit rate, but all it’s doing is adding 0s on the end.

Dithering

Dithering is a fairly counter-intuitive process that involves adding a layer of distortion to smooth out any errors made in chucking away 8 bits of information (when downgrading from 24 bit to 16 bit).

Again, this is something that should be left to the mastering engineer, but if you are mastering at home then make sure you always dither last – that includes after changing sample rate. So, if you recorded in 48khz/24bit and you’re exporting to 44.1khz/16bit you will need to first export at 44.1khz/24bit and then separately dither down to 16bit. Putting a dithering plugin on your post-fader master channel and then going straight to 44.1/16 puts your sample rate conversion before your dithering. Your audio will suffer for it.

Also try out as many dithering algorithms as you can, they do sound different. Noise shaping algorithms generally work best, but it is entirely subjective. My personal favourite is Izotope’s Mbit+ algorithm but I will always audition different noise levels and shapes for each project.

Follow these rules and your sound will come out cleaner, sharper and, well, better.

Great Free VST Plugins

The maxim ‘you get what you pay for’ holds true for most pro audio products, but I’ve recently been pleasantly surprised at the quality of some free VST plugins. Most useful are the free utility plugins used as loss-leaders, but there are also some really talented bedroom programmers out there.

I’ve tried out quite a few over the last few months, and these are my favourites.

Analysis tools

Some people find needle meters somehow easier to understand than the bar meters most DAWs use these days (myself included). If that’s you, PSP Vintagemeter could be the answer for you. Useable in either PPM or VU mode, it’s a nifty way of getting needles into a digital environment.

Voxengo SPANBlueCat FreqAnalyst is a fully customisable spectrum analyser that even lets you zoom in on a particular frequency range for more detailed inspection.

Voxengo’s SPAN is a great all-in-one analysis tool that gives you metering of almost any kind you could want – from standard VU and PPM to different K weighted scales, average values (RMS and crest factors) as well as a very useable spectrum analyser. The only problem is it does seem to colour the sound a little bit when switched on…

Utility plugins

BlueCat’s Gain Suite contains a number of very simple plugins that literally do what you’d expect – adjust gain. This is actually more useful than you might first think, particularly for optimising gain structures when running outboard gear as external plugins from your DAW.

Anyone interested in mid/side processing would do well to download Voxengo’s MSED. Although it’s not too difficult to manually set up a mid/side chain if you know how, this is a great time saver.

The Audiocation Phase AP1 is great for sorting out phase relationships in your mix.

Character

Voxengo’s Tube Amp is great for adding crunch to a signal, particularly when run hot and in parallel. It’s actually surprisingly tube like as well.

The excellent Bootsy over at Variety of Sound has put together three brilliant saturation plugins: the Ferric TDS tape simulator and the Tessla SE and Tessla PRO transformer saturators. The Tessla PRO is particularly interesting as its transient aware.

What free VST plugins can you recommend? Leave your answers in the comments.

Making it Sound Deliberate

Following on from our last post on the importance of knowing the science behind production, we thought we’d take a look at knowing your limitations.

I know we say it a lot, but the advent of home production is great, and as the technology develops and continues getting cheaper it’s only going to get better. That being said, it’s still a relatively expensive way to spend your time, and some things will always stay expensive – good monitors, good outboard gear, anything electrical rather than digital.

You are not Phil Spector

Phil SpectorAny home producer worth their salt knows that they’re limited. You’re simply not going to get a lush Phil Spector production out of a laptop parked in a spare bedroom with an SM58 fed into it. I don’t care how many VSTs you’ve got, you still don’t have a string section in a well tuned room.

But that doesn’t mean you can’t get professional results. The trick is to work within the limitations of what you’ve got.

Sticking with the strings, you can get great sounding strings out of a good set of samples, as long as you don’t try to do too much with them. Sustained chords will usually sound great, trying to pick out a proper melody will often just reveal their inadequacies. Perhaps you’d be better off with synth strings where it doesn’t matter that they don’t sound real?

Embracing lo-fi

Similarly, if all you’ve got is a cheap audio interface and a cheap mic, embrace your lo-fi. It takes good pre-amps and a good mic to make a well balanced ‘big’ vocal sound – no amount of messing around with plug-ins and pre-amp simulators is going to replicate it.

Lo-fi is a bona fide sound. If that’s all you can achieve with what you’ve got, either go with it or go to a professional studio. No one complains that Coco Rosie don’t sound ‘proper’ but they certainly don’t sound like they went to a proper studio. Check this out for some great lo-fi.

Of course, (plug alert) even lo-fi recordings need to be brought up to spec, which is where mastering comes in. Make no mistake, mastering will not make a lo-fi recording hi-fi, but done well it helps make the lo-fi sound deliberate rather than enforced.

And that’s the trick – make everything you do sound deliberate.

The Short Version

  • You are limited by the gear you have.
  • If you can’t get the sound you want from the gear you have, either go to a professional studio or aim for a different sound.
  • Lo-fi can be great as long as it sounds deliberate.
  • Phil Spector is in prison anyway.