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Monday, October 24, 2011
How To Use Compression On Guitar
Compression is a topic that confuses a lot of guitarists. Most professional guitarists will suggest using compression pedals live on pedal boards and compressing guitars in recording studios, but why? For most beginning guitarists, the purpose of compression can be unclear. Let's tackle compression in this post so that it will be more clear to you on your live rig or in the studio. You will find the definition of compression, different compression pedals and studio tools, a demonstration on a pedal board, and tips to recording compression in professional and home studios.
In this article we will first talk about compression in what it is and how it's used. Then we look at the 4 important things you need to know and understand to use compression in your audio recordings correctly.
When you add compression, you add noise. Why does a compressor add noise?
The purpose of a compressor is to reduce the dynamic range of a track or entire mix. This means it reduces the higher levels and brings them down closer to the lower levels. Basically you're crushing down the sound and then bringing it all back up again.
Now the problem is the signal sounds quieter because the peak levels were brought down and will need to be brought back up.
Now the signal is as loud as it was before in the peaks, and the lower-level sections are also louder.
Unfortunately the compressor has no way of distinguishing between the low level noise that you don't want and the low level signal that you do want. Every signal contains some noise. There is no such thing as a noise-free recording.
The job of a good audio engineer is being able to manage all this noise effectively.
When a stereo mix is compressed,, it will be noisier. You can tell how much by looking at the gain reduction meter on your compressor; the maximum gain reduction that it shows is equal in decibels to the amount of noise you have added.
Most recordings use compression. All pop music you hear on the radio uses a lot of compression. Why? Well, we've gotten to a point where it's a competition to see who can make the loudest record!
A good recording engineer can use compression as a very valuable tool, although many musicians that are home recording studio enthusiasts don't fully understand audio compression and what to do with it.
OK, enough babbling... this is what you need to know:
The 1st thing to look at when working (or playing) with a compressor is the "threshold".
This is the point at which the compressor kicks in and starts to do it's thing. If you're using a plugin which came with your audio recording software program set it to the factory default setting. This will be a medium setting so you can go to either extreme and see how it operates. After it kicks in, it starts turning the overall level, or volume down.
The 2nd thing to look at is the "ratio".
The ratio will determine how much level is turned down in the threshold. So when your ratio level says 4:1, that means 4 db of signal is going into the compressor and only 1 db is allowed to come out. Typical settings as on the Bombfactory compressor will be 4:1, 8:1, 12:1, and 20:1. The higher the number the greater the compression.
The 3rd thing to look at is the "attack".
The attack determines how soon the overall level of sound (refer to the "gain reduction" nob) will start to be altered.
The 4th thing to look at is the "release".
The release time means how long until the unit stops altering the sound. A low attack setting will allow more of the initial signal to get through without being altered.
What about a "limiter"? It's a compressor as well. The difference being that we use it for controlling occasional peaks of audio rather than compressing constantly for containment purposes as done with a compressor. So the limiter will start at 10:1 and go up from there, So, say you have a track that over peaked in only a couple places in the whole song, you could put a limiter on it and it would only kick in at those peaks and be totally unaffecting the rest of the time.
*Tip for using compression.
A good tip I learned from engineers is not to use compression on your stereo outputs of your mixing board. So, if you see your needles pinning a bit into the red, instead of throwing a compressor on em, look at which individual tracks are responsible instead.
It's tempting to put the compressor on the overall mix because that's the easy way, but if you work on containing the individual tracks you will get a more natural musical performance element to your mix and more dynamics too.
One integral element in recording is the use of compression, a subject that can at times be confusing for many.
So this latest installment of my blog I want to discuss compression, and I thought what better person to explain it than Mike Senior, author of Mixing Secrets For The Small Studio, which I spoke about a few posts ago.
I put a few questions to Mike about compression, and hopefully his answers will help demystify the topic of compression for you all.
Simply put, what is compression?
A compressor is best thought of as an automatic fader, because it evens out the level of a signal so that you don't need to tweak the channel fader manually. So where you might ride a channel fader to prevent a track clipping while recording, a compressor can handle that automatically.
In mixing, on the other hand, the purpose of the compressor will be to even out a track's levels so that you don't have to continually adjust its track fader level from moment to moment to keep it at the right volume in the mix. People talk a lot about compressors changing the tone of a sound, or making it punchier, or whatever, but fundamentally these are side-effects of a compressor's basic level-control function, and you'll never be able to turn those side-effects to your benefit until you get to grips with the basics first.
How important is compression to recording and mixing?
These days, the quality of even home-studio digital recording equipment has improved to an extent that you can get away just fine without compressing at all while recording -- although some people still choose to do so for aesthetic reasons or to provide more consistent headphone foldback during overdubbing, especially when recording
vocals.
At mixdown, compression is vital to almost every major commercial music style outside the classical sphere. Not only will individual tracks be compressed, but mixed groups of channels will often be compressed further together too, and yet another round of compression may be applied to the mix's main output channel.
What are some simple, basic techniques for understanding and using compression that one can use?
There are two basic principles to bear in mind when starting to use compression at mixdown. First: are you achieving the technical level-evening effect you need -- in other words, do you still need to mess with your fader to keep the track's level solid in the mix?
Second: do I like side-effects of the processing? The subjective sound
character of different compressors can vary a good deal, especially if you're using heavy compression, so if a given compressor is making one of your instruments sound lumpy or unnatural in some way, then adjust the compression settings or switch compressor entirely.
Beyond this, the main thing you need to know is how to adjust the amount of compression (usually via a Threshold, Input, Drive, or Compression control) and how to compensate for any level-loss incurred in the process (usually via a Make-up Gain or Output Gain control). Beware of compressors which provide automatic make-up gain, as these will encourage you to apply more compression than you need, simply because compressing will tend to make the processed sound feel louder.
First, I have very little experience with compressor pedals. Second, the Ego compressor was not some new release for the Nashville Amp Expo.
Wampler Pedals actually had a pretty cool high-gain distortion pedal they were demoing for the first time at the show. The SLOStortion is a surprisingly thick sounding distortion pedal. Not entirely my cup of tea for blues, but I was surprisingly intrigued by it's beefy tone.
I spent a good amount of time in the Wampler room trying out the pedals, mostly playing through their compressor pedal called the Ego.
I've never used a compressor pedal in my signal chain because it felt like cheating. Maybe cheating is the wrong word. I just felt that compression should come from the amp as the tubes are overdriven, so a compressor pedal SHOULD be un-necessary.
However, a clean amp played at relatively low volumes is an exceptional case. The tubes aren't adding any compression of their own, so it's not the "clean" that bothers me, just the lack of sustain. At loud volumes, a clean amp will cause the strings to sustain more, but a clean amp at low volumes is rather plinky.
A compressor pedal, I theorized, could help solve some of this by adding more sustain to the notes. But I didn't want to lose the snappy attack, especially for those plucked Albert King style bends. So I kind of wanted the best of both worlds.
At the Amp Expo, I tried out the Ego Compressor from Wampler, and was delighted to find that it has a "blend" control. This blend allows you to mix the compressed signal from the pedal with the uncompressed original signal. So you retain the snap of the initial picking attack, but your notes will sustain longer, to the degree that you've mixed in the compressed signal with the "Blend" control.
I am in no way a connoisseur of compressor pedals. So when I bought the Ego, I had not done a ton of research on competing pedals. But it did what I wanted it to do, and sounded very transparent. Good enough for me, and I like it quite a bit.
When I'm done with my next lesson series I'll be doing a full review, but the video from the show should reinforce some of what I've written here.
Home recording studio
For those of you who have experience using compression in a recording studio, super sidechain compression might be familiar. This production trick can be very helpful to sound engineers. Check out an explanation and demonstration of super sidechain compression in Pro Tools here at http://erikhawkins.berkleemusicblogs.com/2010/12/27/super-sidechain-compression/.
Sidechain compression is a wonderful production trick. Originally, it was used to duck music behind an announcer’s voice on the radio. Each time the announcer would speak the music’s volume would be automatically lowered. Today, it’s widely used in dance music to create that “pumping” sound in the mix.
Sidechain compression works by using another sound to trigger, or key, a compressor rather than the signal on which the compressor itself is inserted. For example, you could set up a bass line to be compressed each time the kick drum plays. The compressor is inserted on the bass channel, but the kick drum keys the bass compression. This is how you create that ubiquitous pumping bass sound heard in dance music, where each time the kick plays the bass is automatically ducked so that the kick drum isn’t drowned out by the bass tone. It’s a great effect that sounds like the bass line is breathing with the kick drum.
You can also set up sidechain compression using a key sound that won’t be heard in your actual mix. For example, if your kick drum pattern isn’t four-on-the-floor (all quarter notes), but you still want the bass line to have that pumping four-on-the-floor feel. To accomplish this, set up a MIDI track that plays a drum sound (such as a kick drum sample) playing only quarter notes. Then, use this signal as the audio that keys the bass compression, but don’t send this audio to your main mix. In Reason, it’s a snap to set this up using Redrum’s step sequencer to loop a four-on-the-floor pattern, and then send Redrum’s audio directly to an MClass Compressor’s Sidechain Input. I’m attaching a Reason 5 song file for you to check out how this is set up. (You must have Reason 5 or higher to open this song file.)
Most professional DAW programs feature at least one compressor that has a sidechain input. For example, Pro Tools has its Compressor/Limiter Dyn 3 plug-in, Logic has its Compressor plug-in, and Record features the MClass Compressor. While setting up a keyed compressor will vary a bit from one DAW program to the next, the basic operating concept is always the same. You want to send an audio signal to the compressor’s sidechain input, and you may need to enable this input function. Often, you’ll use a bus to send signal to the compressor’s sidechain input. And, you’ll want to set the compressor’s parameters for heavy compression to achieve the most dramatic effect possible. For example, a high Ratio with lots of gain reduction. Here’s a video of how to set up sidechain compression in Pro Tools using its Compressor/Limiter Dyn 3 plug-in.
Hi! I’m Mark Grundhoefer. I wanted to share a little bit of info about my rig, my guitar, and my pursuit of that “holy grail” of tone. It’s taken a long time, and I have a stash of unused/broken stomboxes, but I finally feel like I have a professional sound that can compete with some of the best.
To start off, I use an older SKB board with built in power and a durable carrying case. Seriously - I’ve stood on top of this thing. The built in power is sufficient for most of my pedals but I have a few that need other voltages so there are three wall wart slots in use.
All the connections on the board are custom Lava Cables. These solderless right angle connectors are amazing and I’ve never had a cable go bad. I’ve got a Zaolla cable going from the board to the amp and a Mogami cable from the guitar to the board. Even having everything contained in a covered board my knobs do sometimes get moved during transportation so I use glow-in-the-dark puff paint to mark all my settings. Also, very helpful on a dark stage and it’s easily removed with no harm to the pedals surface.
Pedal order is as follows:
1. Wah - This is a typical Dunlop Wah with a few tweakable knobs that do help in adjusting the sweep. It’s got a decent sound, but not the best. However, I’ve kept it for years because it has a switchless, springloaded system. As soon as you step on it, it’s engaged. No more frantic stomping on the front for 10 seconds and missing the riff.
2. MXR Phaser - I don’t use this pedal very often and don’t have a lot of use for the Phaser sound so the single knob is very convenient. I never play (even if I wanted to) anything closely resembling EVH so it doesn’t make a lot of sense to have his signature pedal, but the script knob is a selling point so that’s why I have it.
3. Keeley Compressor - Simple. Effective. 2 knobs. Compression. There’s not a better sounding compressor on the market. I use it mostly on high gain leads as a boost and of course to round out the sound and get some fat sustain.
4. Xotic RC Booster- Yeah, I got the limited edition sparkle finish. What up? This guy sounds great as a clean boost for riffs that you want to cut through the mix.
5. Xotic AC Booster - If I were deserted on an island…and had power… and a guitar… and an amp…this is the one pedal I’d take with me. Great rhythm and lead overdrive.
6. Rockbox Boiling Point OD - When you order these puppies online they ship to you with a custom paint job. I got lucky - Pink. It may not have the most manly design, but the sound is unbelievable. You’d think you were playing on 11 through a stack of Marshalls. Great high gain sound.
7. EWS Fuzzy Drive - Not too fuzzy and that’s what I like. I’ll use it for a modern bluesy sound. Unlike other fuzz pedals I find the tone knob on this one to be super sensitive which makes it very useful.
8. Arion Chorus with EWS Mod - The Arion Chorus is one of those great pedals that has such a unique sound you can’t duplicate it with any other box. EWS took that great sound and made it better with true bypass and added a Vibe switch.
9. MXR Carbon Copy - Analog delay in a compact box? Yes please! I keep this pedal right on the verge of self-oscillation and use it as a spacey effect for my lead parts.
10. TC Delay - Since the Carbon Copy isn’t used as a traditional delay, I need the TC Electronics delay to fill that role. Everything up to this point in my board has been true bypass. This pedal not only works as a solid delay, with a ton of settings, but also as a line buffer for my signal.
11. EHX Pulsar Tremolo - I’ve really never bonded with this pedal. But I needed a tremolo for one song and found the one sound I needed with this pedal. Are there other useful settings? I haven’t found any. Kind of a one trick pony.
12. Ernie Ball Volume - Passive volume pedal with a tuner out.
13. TC Polytune - If you’ve never used this pedal to tune, you’re missing out. Why didn’t anyone think of polyphonic tuning before? Awesome!
Then it all goes into my Carvin Master Tube Combo. Great tube sound and simple design. Similar to a Twin Reverb. However, this is the next upgrade I want to make. Looking at getting a better combo amp. On top of my amp I have one more pedal velcroed to it. It’s a custom built Reverb unit from John Kasha. I have it running through the effects loop so it stays close to the amp. It’s always on. Just for a little reverb since the amp reverb is pretty weak and unnatural (even though it’s a spring reverb).
My main guitar is a Brian Moore iGuitar. There’s not many guitars out there that are more versatile than this one. The neck humbucker and middle single coil pickups are both Seymour Duncans, while the bridge pickup is a Sheptone. This guitar has an integrated 13 pin midi system that allows me to use my Roland GR-20 guitar synth to get a ton of cool sounds. It’s great for certain gigs to be able to layer a square synth sound with my saturated lead tone. Or put a string orchestra underneath my clean rhythm sound. The guitar also has piezo pickups for acoustic tones. It’s got a great neck and is even lighter than a strat.
This article is intended to address not the parameters of compression, but the types of compression that is acquired through different kinds of gain reduction. GR could be divided into five types based on the electronic method used.
Term Definitions:
GR – gain reduction
VLA – Variable Limiting Amplifier
VCA – Voltage Controlled Amplifier
FET – Field Effect Transistor
Variable Limiting (Vari-Gain) Compressors
Variable Gain compressors include all units that incorporate discrete circuitry other than VCAs, FETs or opto-isolators. “Mu” is a synonymous term for gain in the world of tubes, and it works by re-biasing a vacuum tube to achieve its compression. These units are known to have a softer knee and smoother characteristics. Vari-Gain comps are quite at home on a mix bus, vocals, or bass guitar.
Example: Manley Variable Mu, Fairchild 660 and 670
Voltage Controlled Amplifiers
A Voltage Controlled Amplifier type of compressor is definitely one of the most versatile and likewise is one of the most common. The VCA can rapidly alter its gain level in response to many different detectors looking at the same signal. It is common practice to employ a VCA type of compressor if one is looking for strict control over the level and dynamics of the signal. They can be just as gentle as any other type of compressor. These are well-known to sound great on many different types of sources, from synths to vocals. They are a safe choice for any application which requires the use of compression.
Example: DBX 160, Focsurite Red, SSL G Bus Compressor
Optical Isolators
Often referred to as “opto” compressors, these are isolator type of compressors that use a light bulb (or an LED) to create changes in gain as it corresponds to the incoming audio signal. A photocell (or phototransistor) is then incorporated to track the varying brightness of the bulb and change its gain accordingly. This method is thought to induce smoother characteristics and soften the attack and release times. Compressors using this method are used a lot for bass guitar, vocals, program mix and drums. These compressors offer simple, natural sounding control (unless pressed hard). The compression imparted by these units tends to be very musical due to the use of light transduction. Opticals are also known to be slower and smoother, although colored and aggressive when need-be.
Example: Universal Audio LA2A and LA3A, Tube-Tech CL1B, and Avalon
FET
Field Effect Transistor compressors use a special type of transistor to vary gain. FETs emulate vacuum tubes with a transistor circuit. FET compressors are high-impedance units and have a sound all their own. There are not many examples of these types of compressors because of the expense of the extra circuitry that is needed to operate. These compressors are extremely fast, clean and are studio workhorses. FET compressors are known to be fast-attacking compressors, as well as being smoother and having more control. They are also famous for not really “coloring” the signal, but this can change depending upon which model is being employed.
Example: Universal Audio 1176 and LA Audio Duel II, Purple Audio MC77
Computer-Based/Digital Compressors (Software)
Plugins are digital representations of outboard analog gear, whether in sound and emulation or merely in conception. They offer the ability to process audio in the digital domain under infinitely precise control. One thing to keep in mind with digital comps is that they are an emulation of analog compressors. Meaning, they are not a direct equivalent but an “approximation” if you will.
Hybrid Compressors
Worth mentioning, there are units that include more than one type of circuit design. These often can't be exactly categorized in the above manner.
Example: Empirical Labs Distressor, and certain Neve models
Hopefully this will help shed some light on how compressors work differently from one to the next, and will help you make better mixing decisions.
Compression is a tool that can make a difference on your sound. These resources should help you understand the effect compression has on audio and guitar sound. Whether you are looking for a compressor pedal for your live pedal rig or compressor unit for a recording studio, you should find a good start in your research here.
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fuzzy drive EWS pedal checksound >> youtu.be/yXF5-9pdGes
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