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GLYN CORNELIUS: Direct Injection

Sounding Off
Published November 1997

Dull, lifeless sound you can't do a thing with? Your problem could be direct injection — the scourge of modern recording, claims Glyn Cornelius.

Now that digital‑quality recording is within reach of the masses, many readers of this magazine will have access to high‑quality recording equipment — a hard disk recorder, or a system on your PC. I'm sure that users of this equipment will agree that while the recording quality itself can be excellent, the finished mixes often sound flat and unrealistic. Nothing has any depth and, no matter how much reverb you use, the sounds seem to be welded to the front of the speakers. This may be CD‑quality recording, but when you listen to a 'real' CD afterwards the difference is huge.

There are many reasons for this 'home studio' quality, but I believe the main one is the way instruments are direct injected and not 'recorded'. Many acoustic guitars, for example, are now fitted with piezo pickups (aptly pronounced 'pisso'), which turn the vibrations of the guitar top into an electrical signal. These are designed to replicate the acoustic sound of the guitar — but although they are useful live, in the studio they are a disaster! Can you imagine an engineer going up to Elton John and saying "It's OK, mate, we're going to put this transducer round your throat to pick up the vibrations, so you don't have to wear headphones and we can make as much noise as we like"? It's the whole instrument that makes the sound, and just putting a sensor on the vibrating component is only going to give a rough approximation of that sound.

I recently recorded a friend playing his £1000 Takamine acoustic guitar. He wanted to use the built‑in pickup, because he thought it would be too much hassle to set up a mic, and that it would pick up too much noise. We finished the track, but the piezo guitar sound made the whole thing sound 'false': it could have been recorded in outer space for all the ambience and 'air' it had!

Soon afterwards I needed an acoustic guitar for one of my recordings, so I went and bought a £50 steel‑string and ordered a £20 electret mic from Maplin. After putting the mic six inches in front of the sound hole and adding some reverb, I had a fantastic sound — it was full of life, and when you listened you could imagine a real guitar being played.

The reason my cheap guitar and mic blew away the far more expensive guitar was that I had recorded a 'sound' and not an electrical signal. I realise that the microphone generates an electrical signal, but the point here is that what you are recording should exist as a sound first. This is so crucially important it should be embossed on the front of every multitrack. It really annoys me when bands (usually American) go into expensive studios with any mic available and then DI their acoustics. Setting up a mic isn't a hard job, and it gives far better results than direct injecting ever will.

Electric guitars are the same. People have become so accustomed to DI'd sounds that they've forgotten how good a guitar can sound. Instead of plugging your guitar processor into the desk, stick it into a guitar amp first and set up an SM58 in front of the grille cloth. The limited response of the amp will help to filter out all the digital rubbish that comes out of most guitar processors, as well as giving depth and power to the sound. It doesn't have to be loud: normal bedroom volume will do, and if you point the mic away from your monitors you can do without headphones and monitor live. How people could ever expect 'speaker simulator' programs to work is beyond me. The speaker is a transducer, an energy converter that converts electricity into sound; you can't replicate that with an EQ curve! Keyboard sounds can also be put through speaker systems and miked up (I hate writing the phrase 'miked up' because the word microphone doesn't have a 'k' in it, and if you use the 'c' it looks as if the heavy rodent brigade have done you over). Once again, this helps filter out all the hiss and noise from your synth. At least sampled keyboard sounds have usually been through a mic at some stage, so even they can be more realistic than real instruments that are DI'd.

Building up a multitrack recording out of 'real' sounds is very rewarding, and the finished mix will be light years beyond one that is made up of DI'd instruments. It will also be easier to mix, because you can't possibly create a convincing mix out of sounds that weren't convincing in the first place. Can you imagine buying a painting from an art gallery that came as a paint‑by‑numbers kit? This is what a DI'd recording is: a half‑finished job that relies on the listener's system to turn it into a sound.

So next time someone comes into your studio and gives you a lead from their acoustic or white noise generator (sorry, guitar effects processor), tell them that you record sounds, not waveforms.