Guitar Amp Recording Part 1

Article written by Mike Senior, SOS

I love reading interviews with engineers and producers, but the more of them I read, the more I come up against the basic problem that my brain is like a sieve. I'm forever thinking to myself "I really must remember that technique", but unless I dash off and use it right away the knowledge just skips out of my ear and heads for the hills, probably glad to be free. And even if I vaguely remember reading a fascinating passage about de-essing nose-flutes, I'm damned if I can recall where I read it or who recommended it. A few months ago, I decided that enough was enough, so I began to trawl systematically through Sound On Sound's interview archive, collating and comparing different producers' views on a variety of recording and mixing topics. Being a glutton for punishment, I also waded through the 35-odd interviews in Howard Massey's excellent book, Behind The Glass.  

The first subject I concentrated on is (you guessed it) recording electric guitars. What became immediately apparent was that there was a huge range of different techniques being used, and also that there were strong differences of opinion between different professionals, which left the question 'who do I believe?' The only way I could answer that question was to put the different techniques into practice in the studio, and then A/B them to sort the sheep from the goats. Now, I'm sure that you're all sensibly busying yourselves with making music, so your lives are, frankly, too short to be sifting through more than a half a million words of interviews. Therefore, I'm going to try to digest what I've discovered during this process for the benefit of those less sad than me! I'm not about to dictate which technique is 'best', though, because if reading this many interviews has taught me anything it is that people will always disagree on what constitutes a great sound. Instead I've recorded a number of different audio examples to allow you to judge for yourselves, just as I did, which techniques are likely to make a real difference to your own productions. I've peppered this article with a number of boxes giving details of these files.  

Getting it Right at Source

About the only thing that all these producers have tended to agree on across the board is that you should try to get your guitar sound as good as you can before you even think about recording. "The stupidest thing that any musician can do," remarks Tony Platt, "is to just plug in and play and say 'make that sound good'. It doesn't work like that. I will always say to the guitar player, for instance, 'Is that sound coming out of your amplifier the sound you want to hear? If it isn't, show me what it is and we'll try to get somewhere close to that before we even put a microphone on.' It's a waste of everybody's time to sit there tweaking stuff until somebody says 'Oh that's good.'" There is clearly a great deal that the guitarist can do for the sound by changing guitars, strings and amps, but from the perspective of the recording engineer it's also important to think about how the guitar cab is interacting with the room it's in. For example, Roy Thomas Baker (producer for Queen, T'Pau) mentions that he sometimes sets up the same guitar cab in different rooms because of the effect on the sound. Even if you're restricted to one room, a number of producers suggest trying out different positions of the amp in the room. Tony Visconti (producer T-Rex, David Bowie, Iggy Pop): "It's not so much that you're miking a guitar — you're miking a guitar in a room. I had a cellist in here recently, and I moved her until I got a good sound. Once I put her in one particular corner, her cello just sang — the room just filled up with the low end, and the sound exploded!

A person who hasn't had years of experience might not have thought of doing that, but I could tell there was something lacking when she was in the centre of the room. That's mic technique. It's not so much the instrument; the room is very much part of the sound." One reason why the sound changes in different parts of a given room is that sound reflecting from room boundaries reaches your recording microphone later than the sound travelling directly from the amp, causing phase cancellation — in effect a series of peaks and dips in the recorded frequency response, the spacing of which is related to the delay between the direct and reflected sounds. Keith Olsen (producer Fleetwood Mac, Scorpions) suggests lifting and/or tilting the amp to minimise the effects of phase cancellation. "Leo Fender put those legs on the sides of a Fender Twin, and he did it so the guy in the orchestra could actually hear it when he was playing soft. But the other reason is that when you put a mic up against an amp tilted that way... you don't get phase-cancellation problems off the floor and wall. Let's take it one step farther. Let's lift that speaker cabinet off the floor and put it up on something that is stable enough to be able to give the speakers a platform to work from, but where... the reflected sound is going to be so far down in volume to the direct, it's of no real consequence... All these things start adding together into mic technique, stuff that you learn over years." Also using his room to advantage is Jay Graydon (producer Al Jarreau, Airplay) who talks about placing a guitar amp on his studio's drum riser for certain sounds. "The riser eliminates low-end coupling with the floor. I am looking for a sweet mid-range tone, so as to not take up too much room in the track, meaning that I do not want low-end information for solos."   The following audio examples demonstrate the impact that the choice of recording room and the position of the amp can make. All the examples were recorded with the same guitar and amp (a Fender Telecaster and Fender Twin Reverb), and were miked with the same SM57, placed directly on axis to the centre of the speaker cone and six inches from the grille.

Multi Amp Sounds

Several producers like to create larger-than-life recorded sounds by splitting the guitarist's instrument signal to several different amps, which are then recorded simultaneously. Joe Barresi (producer Queens of the Stone Age, Limp Bizkit) is a devotee of this tactic, and uses a dedicated guitar splitter box, such as the Little Labs PCP Instrument Distro or Systematic Systems Guitar Splitter, for the purpose. "In choosing the amplifiers and speakers, it's important to remember that larger speakers give a more compact, tighter sound. A tiny amp turned all the way up will give a more blown-out sound." Mike Hedges (producer The Cure, Manic Street Preachers) also uses this idea a great deal, and explains how it really comes into its own at the mix. "You've got two or three tracks of guitar: one clean, one medium — say, half-driven — and then one really driven. As the song progresses, you might use the nice clean track during the verse, as you're coming to the bridge you fade in the heavier guitar sound, then back it off a bit, into the chorus with everything full on, then back to the next verse and drop it all out. It's all done on one guitar track, so it doesn't sound like you've done 10 guitar overdubs. It has a different quality, it sounds like a live performance, but you've got real dynamics in the sounds. It's a very effective technique." On a practical note, Steve Churchyard (producer The Stranglers, The Pretenders) has this to add: "You'll want a good A/B box so that you can split the guitar feed to the two amps and obviously use the shortest [cable] run. Ideally have the amps in the control room and run the longer leads to the speakers." The first thing to say is that every model of mic sounds different, and I'm not going to try to do audio examples of all the mics mentioned in this article (if you'd like to compare how a large number of specific mics sound, check out the 3D Audio comparison CDs available at www.3daudioinc.com). However, to give an idea of the kinds of differences engineers work with, I recorded the same guitarist with five different mic types, as follows:

These are recordings made by five mics set up on axis as close as possible to each other. They were positioned at the centre of the speaker cone at a distance of around six inches from the grille. The mics were: a Shure SM57 dynamic and a larger-diaphragm Sennheiser MD421 dynamic; an AKG C414B XLS large-diaphragm condenser and a Shure KSM137 small-diaphragm condenser; and an SE Electronics R1 ribbon. Because all the mics were recorded at the same time, you can try mixing and matching them (as discussed in the article) by simply lining up the audio files in your MIDI + Audio sequencer, without serious phase-cancellation effects. These examples illustrate the range of sounds available from two common mic pairings discussed in the article: a Shure SM57 with a Sennheiser MD421 and a Shure SM57 with a large-diaphragm condenser mic (in this case the AKG C414B XLS). At the start of each audio example only the SM57 can be heard, but then the other mic fades in until, by the middle of the example, both mics are at equal level. Then the SM57 fades out during the remainder of the audio example. D112 C418 D1142+C418

Here, I recorded the same guitar cab with comparatively dark and bright mics in order to try out Steve Albini's dark/bright-mic approach. The mics in question were AKG's D112 kick-drum mic and C418 clip-on snare mic, both on axis at the centre of the speaker cone at a distance of around six inches from the grille. You can hear the range of sounds available from mixing these two mics in the third audio example, which starts with only the D112, but then fades in the C418 until, by the middle of the example, both mics are at equal level. Then the D112 fades out during the remainder of the audio example. Part 2 coming next week!

Thanks to www.soundonsound.com