Notes on using a mixing console. Sorry they're a little rushed!

I've been learning about mixing techniques and mixing desks. They can look pretty bewildering (and can be like that to operate too) but here are my notes about mixing.

 I missed my lesson so my sources are few but you can find the information below on an easy to watch video channel at the link below:

Youtube playlist for mixing

Also, there is a great booklet you can view online or even order a paper copy (like I did) free of charge called Soundcraft Guide To Mixing on their website.

Soundcraft Guide To Mixing

MICROPHONES - types and positions

Microphones

Get the right mic. Dynamic are tough and cheap and need no external power supply and are ideal for all round use. Condenser mics are much more sensitive to low levels and higher freqs. Must be powered with batteries or phantom power. Omindirectional is sensitive from all directions. Great for ambient sounds and group vocals but can be prone to feedback. Cardiod mics have a heart shaped response pattern - most sensitive to front and sides. Great for avoiding spill. Hypercardiod is more directional and great for live vocals.

Phantom Power

Condenser mics need power. Switch it on for condenser mics without batteries. Don't use global on non-phantom power sources as it can cause damage.

THE MIXING CONSOLE - Channel strip / EQ

Using a mixing desk 

What does a mixer do? All mixers are the same, or at least have the same components. An audio mixer brings everything together so it sounds good. It can seem confusing but they're divided into groups. Every sound input has its own controls, called a channel strip. Each one is the same. 

The mixer channel strip

The channel gain sets the sensitivity of the signal. Low level signals are from mics whereas keyboards, synths and drum machines are louder. Gain setting must be sorted for all channels. HPF – high pass filter cuts out low freqs but lets others through. You can clean up boomy instruments or rumble from air con or stage noise etc with this. Don't use on bass guitar or kick drum. EQ section is crucial. Can change character of sound. Use in moderation unless its for an effect. Split into bands controlling a range of frequencies. The more bands the better for eq as a general rule. Aux sends control the amount of signal sent to external effect or stage monitors. The pan control is for the left and right settings in the stereo mix and also used with the routing selectors to send audio to group faders and outputs. The routing selectors determine which subgroup its going to. The solo button is for isolating a single channel. PFL (prefade levels) isolates the signal so you can EQ or get levels without altering the main mix and you can use PFL to find dodgy parts. This means you can leave it playing but still single it out. Channel mute turns the channel on or off. Best to leave it in mute if you're not using it. Faders set the level of an input signal in the mix. Different to gain. Gain makes sure the signal into the strip is fine. But the faders level it with other parts. Never use faders to correct a weak signal. Gain should be uniform throughout. 

Using EQ

EQ is frequency selected gain. Boosting means potential for feedback so mute mics not in use. To get an extreme EQ effect use two mono inputs.

SECTIONS OF THE MIXING CONSOLE

Control layouts

The main section of a mixing desk. Each audio source comes in through channel strip. This is most of the mixer. Sometimes you can control a group of sounds. All drums can be put through a group mixer which allows for easier control. The master section is where the mixed sounds end up and have a headphone mixer, the control room sound and the final mix. Also has output for tape decks, CD's, computers etc. 

The Master Section

This is where you control and monitor the mix and send out. It controls level of stereo mix. Mix outputs control the level of the final stereo mix. It also has the engineers control room, which is not sent out but instead used for loudspeakers or headphones. It can also monitor solos or whole mix. If you want to play music out to an auditorium before a show, plug into two track tape returns. The aux masters control the level of audio to external effects, which are on the auxiliary sends. AFL lets you monitor signal from auxiliary masters. Meters normally show the mix output levels, unless soloed when they show the output for the soloed instrument only. Stereo returns are for outputs from effects. Audio from stereo returns can be routed to stereo mix or subgroups. Headphone socket is for headphones. Need to be closed type. 

RECORDING TECHNIQUES FOR DRUMS / GUITAR / VOCALS

Connections

Don't skimp on cables and connectors. Always balance cables for mics. Keep cables as short as possible. Stage boxes are useful. Keep power supplies away from console. If audio and power cables cross, arrange them at 90 degrees to avoid hum. When the venue has 3-phaser power, don't share with lights as they give hum. Don't disconnect the earth to reduce hum – its very dangerous. When using radio mics put the receiver on stage and run the audio back to mixer using a balanced DI box. Keep unbalanced insert leads away from mains. 

Connecting Equipment

DI boxes turn a low level (direct injection) unbalanced signal, from guitar or bass perhaps, into a balanced one through XLR inputs. They cut out noise and interference. Best ones use phantom power and are active. It's not good putting directly into a desk. Fx units need to get signal from desk and back into it. They have inputs and output. Connect to a post fader aux output. Left and right should be into stereo returns or inputs. Stereo channels have fewer facilities. Connect a compressor to an insert jack. They look like normal leads but are Y shaped send and return jacks.

Signal Sources 

If gain setting is too low, the signal will be noisy, too high and it could distort. If gain settings are wrong on one or more channel it will add in the final mix. Most mixers have mono and stereo inputs. Normally XLR on mic inputs. Mic inputs are mono. Line inputs are for sound generators such as synths and keyboards. As a rule you shouldn't use line inputs with mics as the signal is lower than line inputs are designed for. It's OK for stereo to be put into mono but try and get stereo. You can also use two mono signals panned hard left and right. The insert point is for compressor and limiters etc. Insert is both an input and output and needs a Y insert cable. Its as if the external processor is part of the strip when using inserts. Direct out is for audio to go into multi track effect or recording device without it being mixed by any other inputs. 

Using FX

Music sounds different in live venues to studio. It can be dull and lifeless so put some FX in. Reverb is most common and essential as it simulates venue sounds. There is no substitute to experimentation. Listen to recordings. In a live venue it has its own reverb. You cannot turn it down. But EQ, levels and reverb can compliment that natural sound. Don't put much reverb on low freq sounds such as kick or bass guitar as it can sound muddy. Delay can thicken a sound with a short delay time and can simulate double tracking. Echo is a longer delay which is good on vocals or guitar and is often matched to tempo of song. Chorus and flange is a very short delay. Flange also uses feedback. Chorus is often used on guitar, flange is good on electric piano. Both work well on synths and fake strings. Modulation can create a swirling effect. When using a mono PA system make sure the effects sound ok when not in stereo. To set up an fx unit, connect to a mixer. Set the unit to give full wet signal. Got to the working channel and set fx post fade aux send to max. Then select AFT and set it to zero on meter. Adjust input level and fx level until the meter reads zero. You can then use the mixer Afl meter to monitor FX levels as they will be calibrated. Release all AFL buttons and adjust the fx returns controls until the effects sounds right in the mix. FX units are always used on post fade aux. So the amount of signal sent to the fx unit is proportional to the position of the fader. If you didn't do it you'd still hear the effect when the dry sound was faded out.

Signal processors

Signal processors work on the whole signal whereas the effects work on dry part and is sent & mixed back with original dry signal. FX are connected by aux sends, signal processors are on inserts. Signal processors are more about getting good quality audio whereas effects are more creative in application. Graphic EQ can adjust a large number of fixed frequency bands. You can see the shape of the EQ curve from the shape of the EQ controls. They are useful for isolating and notching out feedback. Parametric EQ also give you the chance to change the width of the frequency band. This can be used to get rid of a resonance, which means you can tune it and narrow the freq band so it only affects the band you want to adjust. Noise gates allow sound of a certain level through and stops the rest and is good for muting background sounds. It functions as an automatic mute control and is best for drums (but not overheads). Compressors reduce the difference between loudest and softest movements. Ratio is the amount of compression. Used a lot with singers and bass guitars. Limiters are like compressors. They won't let anything through the threshold at all. They can stop feedback and overloads at venues. Use an insert cable plugged into the insert point. Can be mono, group or mix insert point. Set the processor to unity gain (no additional gain or cut) and adjust to get the sound you want. Re-adjust mixer input and output levels for zero on meters.

Setting the Mix

Turn down amp gain before switching the mixer on. Set all controls to flat or neutral position. Then set each channel's gain using the solo button. If low frequency background noise is a problem, use high pass filter on mic channels. Don't use HPF on kick drum or bass guitar. 

MONITORING

Monitor mixes

When you play in a band on a stage, monitors really help! The main mixer can be set up with the mixer or with a separate desk. Use pre fade aux to set levels of instruments in monitors. You can have as many monitor mixes as you have prefades. They come out of the desks by the prefade aux sends. It's a good idea to put a graphic EQ on each monitor output so you can ring out the system but you must do final ringing out with monitor and main pa set to normal levels. Wedges are most used. In ear monitors are good and becoming more common.

LIVE MIXING AND MINIMISING FEEDBACK

Mixer outputs

You are more likely to blow speakers with an underpowered PA than overpowered speakers due to clipping effects. When choosing speakers and PA get some proper ones that are robust and cope with the whole band. When choosing speakers choose dedicated PA speakers. When choosing headphones avoid open backed ones. Setting up a basic mix Mixers can only work with the right audio level. Use input gain to get the levels right. All components make electronic noise so set the levels so you get the highest level without distortion and then back off a bit. Press PFL solo on channel you're working on. Adjust gain until yellow starts show, between 3 & 6. Now release the PFL. This also means the meters give more information.

Minimising feedback

Turn down or mute mic channels not in use. This will also reduce spill. Move PA speakers as far as possible from the mics. Deaden the back-drop with damping material. Don't boost EQ if you don't have to, cut instead. Place stage monitors where they wont be picked up by mics and set them as quietly as practical.

Ringing out system before sound check. Put a graphic EQ inside mixers insert points. Zero all Graphic EQ bands. Turn up amp volume until the feedback starts to ring and then turn back until the ringing does not turn into feedback. Then adjust first graphic EQ to max. If the system does not feed back then this is not a problem frequency so put it back to zero. If you do get feedback, reduce the gain at that freq. Do all the bands on the EQ. Test any effect and check the balance between dry and wet sounds.

Tips for Live Mixing

Try to put the mixing desk so you hear what the audience does. Switch power amps on last. Don't put vocal mics right in front of drums or guitar amps. Make sure the speakers are aimed down at the audience and nothing is in the way. Set vocals first and pan towards the centre. It’s better for a natural sound and a better signal. Go easy on reverb. Most venues already have it. Don't use reverb on low pitch sounds as its muddy. Too much kick or bass can overload a PA, which can ruin a vocal sound with distortion. If you get this then roll off low-end frequencies. Keep the back line levels down and let the mixer do the work. Leave some gain in hand so you can increase levels during a show. Sometimes some instruments can be treated as groups of sounds. These can be sent into a sub mixer before bringing them into a desk.

Again, apologies for the rushed notes but I've been up against it a little what with college work, sick kids, minor alterations to my house, backstage theatre work and general making music. I'll blog again soon where i hope to talk about theatre work, the course and maybe about childhood heroes and scandal. Hmm I wonder who that could be?