AFX Compression Tips (including the new 9.02 features)

Radley

Experienced
AFX Compression Tips including the new (9.02) features

Compression is a very deep & complex topic to tackle, and so I am taking liberties to omit much of the technical/non-essential stuff, and trying to focus on the easiest explanations & techniques to achieve great sounding compression without all the questionable folklore and 'hocus pocus' often associated with the subject. The aim of these tips is not to give people 20 ‘magic’ compression settings, but rather to help the user find the compression they prefer, and understand how it is attained. This will involve a certain amount of experimentation to achieve the goal, so give yourself some time and enjoy the process!

The obligatory ”Jump Start” (for those who need compression now!)

Insert a Compressor block placed first in the signal chain and select the Studio type with Auto engaged, along with these settings:

Threshold=-45/Ratio=3:1/Detect=Peak/Look-Ahead=1.0/Mix=100%/Filter=500/Knee=more soft/Makeup Gain=On.

Now just fine-tune the Threshold parameter to your preference (larger negative numbers increase compression). So easy a Cave Man could do it! I highly recommend that folks follow through by reading this or other articles that explain the basic operation & theory of compression. Because of the AFX’s newly added compression features, it’s actually pretty hard to get bad sounding results once you understand the basics.

Note: All compressors are affected by the signal level at their input - keep this in mind when changing any levels or EQ feeding into a compressor.

Essential Terms: (note - this list of terms & their descriptions is not ‘exhaustive’ - it is intentionally simplified)

Compressor/Limiter - These are really ‘twins’ with somewhat different settings. A full-featured compressor can easily be set to mimic a limiter by using very fast attack & release times, and setting the ratio to infinity (20:1 or higher) - this effect is sometimes called ‘brick wall’ limiting, because it allows no level deviation above the threshold setting. A serious compressor offers more musical effects by giving us adjustable compression ratio, attack time, release time, soft & hard knee, etc. The end result is a more controlled output level, additional sustain and smoothness, and a more punchy, in-your-face sound when needed.

Compression/Threshold - Either of these parameters controls the amount of signal compression with one minor difference: A typical Compression control (most stomp comps) does not reduce the output level & therefore requires no makeup gain, whereas lowering the Threshold control (most studio compressors) to achieve more compression also lowers the output level - hence the complimentary makeup gain control.

Compression Ratio - Perhaps it’s easiest to think of this as a ‘blend’ control with a ‘brick wall’ limiter at one end (CW) and the unaffected guitar signal at the other (CCW). As you might imagine, the in-between settings are where most of the magic happens, with 1.5:1 up to 6:1 being the most popular and natural-sounding. Many people make the mistake of setting this parameter too high and wonder why the sound has no dynamics - with a setting of infinity, you eliminate all dynamics above the compression threshold!

Type - (Studio & Pedal) A typical studio compressor has very low noise & distortion specs, and allows a lot of control over its many parameters to adapt to almost any instrument or sound. A typical Pedal comp is designed mainly for electric guitar or bass usage, with most of the parameters preset by the manufacturer. They tend to be a bit noisier and are more prone to various types of distortion, producing a ‘hairier’ sounding effect. The AFX Pedal comp is not noisy, but it does have this ‘hairier’ tone, and it now (9.02) has a Look-Ahead feature that really smoothes everything out nicely.

Attack Rate - This is the amount of time the compressor will allow a signal to pass before beginning it’s ‘clamping’ action. Very long settings will make the attacks sound too hard & clumsy whereas very short settings can cause some compressors to distort. Note: the AFX attack & release controls are as rates, not times, and therefore the higher the setting, the faster the response (the opposite of many compressors).

Release Rate - This is the amount of time the compressor takes to loosen its ‘clamping’ action. A long setting will be very gradual whereas a short setting is very quick. Too long of a setting makes things sound flat & unexciting whereas very short settings can cause some compressors to distort. A short setting can have the effect of emphasizing the note attacks because its fast enough to ‘reset’ or ‘zero’ the compression cycle between each note. Note: the AFX Attack & Release controls are as rates, not times, and therefore the higher the setting, the faster (the opposite of many compressors).

Look-Ahead - This somewhat rare feature is outstanding because it allows the compressor’s ‘brain’ to know what’s coming in advance, which facilitates an extra level of smoothness and consistency. I find that a setting of straight up (1.0 ms) works well for both the AFX studio and stomp models.

Auto - This mode lets the compressor’s ‘brain’ set & vary the Attack and Release times (regardless of where you have them set) according the dynamics of the input signal. This feature is only as valuable as the ‘brain’ that analyzes the signal dynamics - some comps do it well while others just sound awful (the AFX’s Auto mode does a very nice job).

Mix - This has a similar sonic effect as the Ratio parameter. It blends the compressed signal with the direct signal which in effect, lowers the ratio - the more direct signal, the lower the compression ratio. This is the idea behind the Barber Tone Pump pedal & others.

Knee - This parameter ‘softens’ the sound of the compressor as it transitions around the threshold corner point, or ‘knee’. No need to get more technical, just A/B the sound between hard knee and softest knee and you’ll hear & feel the effect. A lot of country players like the snappy hard-knee response, while jazz players would usually prefer the soft-knee approach for a less obvious effect & somewhat fatter tone. I like to use both types!
Note: Vintage studio comps (and most stomp units) are hard knee - the soft knee option was later made popular by DBX & others.

Detect - (RMS, Peak, RMS+Peak) These are different ways of detecting/analyzing the signal to be compressed, with each method having its own sonic characteristics. To my ears, the RMS has more of a thicker, soft-knee sound whereas the Peak detection has more of a hard-knee character, with a bit more sparkle/jangle. Cliff’s unique RMS+Peak setting gives us the character of both, depending on the dynamic content of the input signal - very cool! Simply use your ears to ‘pick a flavor’ you like - they’re all good!

Filter - This feature allows us to keep the powerful lower frequencies from reaching the compressor’s detection, thus reducing their effect on the gain reduction. This can help eliminate unnatural ‘pumping’. To me, 500z is a good starting point for hearing the affect. Keep in mind that as you increase this parameter you may need to lower the threshold a bit to maintain the same amount of compression.

Factoid: Compressor distortion is lowest in the lower ratios and increases as the ratio is raised.

---------------------

Compression Placement:

There are two types & placements of compression modern guitarists use to tailor their sound:

The First and most important is compression before the amp - (I prefer it to be the first effect in the chain for lowest noise)

This is where we want to place primary compression. It can be subtle or it can be squeezed to death, but this is where the main compression usually happens. The great guitarist for ‘The Fixx’, Jamie West-Oram is a compression hero for many players, because of his aggressively compressed clean tones (check out ‘Saved by Zero’ & ‘One thing Leads to Another’). As many modern guitarists use distorted tones to define their sound, Jamie used accentuated clean compression to drive his masterfully composed rhythm parts, and they had worldwide impact! Jim Messina also got some great compressed Telecaster tones back in the day. But another school says the best compression is the one you don't hear - the one that doesn't draw attention to itself, and there is much merit to that approach as well. I like to use both obvious and subtle, depending on the music - It's all good.

The Second type of compression comes after the amp & post EQ - (many players don’t require this post compression)

This compression is meant to be more of a ‘containment compression’ - to make sure that the low frequency buildup from overdriven amps & post EQ doesn’t overwhelm the system, as well as periodic level peaks in the midrange. It can also be used to mimic amp ‘sag’ with careful attack & release settings. This compressor must be set very differently than the first one - it should be set to effect only the level ‘peaks’ created by the amp’s internal EQ/Compression, and any other processing following the first compression stage (Toto’s Steve Lukather was fond of using this post-compression technique). Normally. this would be something like a 3:1 ratio that only activates when the level goes beyond the preset maximum. This is not the place to add loads of compression because of unnatural artifacts & the accumulated noise that would also get boosted. Our little friend, the (bass) Filter can be used to good effect here to keep the low end from ‘throbbing’ too much. It is very important to remember that any amp level or substantial EQ changes will effect the post compressor’s response, so always listen carefully after you make such changes.

Thought for the day: NO compression is better than BAD compression.

---------------------

AFX Compressor programming....the Easy way!

We all learn fastest by doing, so let’s dig right in & turn some knobs. Go to a clean, fairly dry preset or create one - this will be saved afterwards so you can easily revert back to the settings below. Let’s start with an AFX Compressor block placed first in the signal chain (for the best signal to noise ratio), with these settings: (round them off to the nearest number on the AFX as needed)

Type: Studio
Auto: Off
Threshold: -50
Ratio: 1.5:1 (1.5 to 1)
Attack: 7.99
Release: 10
Knee: Softer
Makeup: On
Detect: RMS
Filter: 500z
LookAhead: 1.0
Mix: 100%


(The other parameters aren’t so important now & will be tweaked later)

Save or copy this preset & name it “Comp 1”

Now play your instrument with these settings, comparing with the compressor bypassed. The difference is pretty subtle but it’s there, especially on the trails of the long notes. Now begin inching up the Ratio parameter as you play, testing at 2:1, 3:1, 4:1, 5:1, 8:1 and 10:1. Do the same test again paying careful attention to both the sound and the feel of each setting, and pick a favorite. If you are like most people, you will probably prefer a setting somewhere towards the center. Congratulations! You have just programmed a very versatile compression patch that can cover a whole lot of territory, all by simply changing the Ratio parameter. With the Ratio lower, the effect is more subtle and natural - with the Ratio higher, the effect is more pronounced and aggressive (freaktone, anyone?) You may need to increase the level slightly to maintain the same apparent level as you increase the Ratio setting.

Now it’s time to start experimenting with the other parameters to learn how they affect the sound: (one at a time, please!) Listen to each change numerous times until you really hear the difference before going on.

Try setting the Attack to 9 & Release to 6.5
Try changing Detect to Peak, then RMS + Peak
Try turning off the LookAhead
Try all the other Knee settings
Try the Filter at 10z (off) and then 2kz (you may need to lower a little amp bass at the 2k setting)
Try switching Auto to On

If you find variations you really like, you should save them also - this way you can come back later (with fresh ears) compare and pick your favorites, and analyze what parameter settings made you like them.

No one can truly ‘teach’ what works for you, because it’s your ears that ultimately determine what’s good or bad - you just need experiment enough to where you:
(1) know what you want to hear, and
(2) know how to get there with the parameter settings.


Now let’s analyze what we’ve done and why:

We started with the Ratio at 1.5:1, a very low Ratio setting. This was so we could hear the affect of very light compression, yet with some sustaining quality. We also went with preset Attack, Release, LookAhead, and Filter at settings I felt would work with all the Ratio settings. As we raised the Ratio, we started to hear more of the compressed signal and less of the direct, producing a more noticeable affect. As we approached the maximum setting, we started to hear a very squashed sound which resembles certain popular stomp compressors (but without the accompanying distortion).

Now let’s repeat the above experiment, but with the Ratio maxed at 20:1 and the Mix on 40% and then slowly working our way up to 100%, again focusing on the sound and the feel as we play. This is very similar to the first method, yet they seem to have a slightly different sound. It is important to learn the Ratio method because many compressors do not include a Mix parameter, including the current AFX Multi-band Comp.

Comments on settings:

Attack - We want to set the Attack fast enough to sound smooth & natural, but we want it to be long enough to attain the desired degree of punch & fatness.

Release - While I tend to prefer fast settings, they all are useful except very slow settings, which can cause the sound to become lifeless & ‘flat’.

Ratio and Mix - I link these two together because they have similar affect. In general, the lower settings sound less ‘effected’, and preserve more of the original dynamics, whereas the higher settings sound more extreme and ‘in your face’.

Generally, as you increase the Ratio (or Mix) parameters, you can raise (less negative numbers) the Threshold and vice-versa to maintain a similar amount of sustain. If you like the basic response & feel of a particular Ratio, but want more or less sustain, simply adjust the Threshold to your liking - do not control the sustain by simply raising the Ratio, because you will also be changing the dynamics and feel - sustain is best controlled by the Threshold setting.

Makeup gain - This is a cool feature because it helps keep the output level ‘in the ball park’ regardless of Threshold & Ratio settings. I recommend leaving the Makeup engaged, so you don’t have to constantly change the output level as you tweak. Although the AFX’s Makeup feature works well, there still will be times when you need to touch up the output level.

---------------------

Extreme Compression - Using the higher Ratios and series (back to back) compressors:

When using the higher compression ratios, namely 6:1 to 1:20 (for a single compressor), the effect produced is increasingly less forgiving to careless settings in the other parameters. This approach can also involve multiple compressors in series, which can impart a whole new depth of ‘squishy’ goodness. A single compressor can be made to sound pretty extreme, but sometimes it’s at the expense of adding unnatural/ugly artifacts to the signal. Two compressors in series can overcome these negatives while adding an extra layer of depth and complexity - what’s not to love?

‘Rules of Engagement’

* For a single-compressor extreme application, the Look-Ahead and Filter parameters are very helpful for maintaining smoothness & minimizing pumping and ‘thumpy’ attacks.

* For a series compressor application, the settings of each compressor must be less extreme than in single mode (the effect gets compounded), and the output level of the first compressor will greatly affect the operation & effectiveness of the second compressor. This method usually provides a fatter and smoother result, albeit slightly more processed-sounding. Generally, the first compressor should have a somewhat higher Ratio setting than the second. Also, when using dual series compressors, they should usually be back-to-back, with no effects or blocks in-between.

* When using a multi-band comp as the second compressor, it is easiest to control it’s amount of compression by changing the output of the first compressor, thus avoiding multiple instances of adjusting all three bands of parameters while tweaking. (I believe the MBC is soon to be updated to share the newest features of the standard comps. ;)

* I do not recommend using the Look-Ahead feature on both series compressors, as latency could become an issue. As a rule, Look-Ahead would only be applied to the first of the compressors for a smoothing effect.

* With this more aggressive hi-ratio compression, the Attack, Release, Knee & Detect parameters become considerably more apparent and critical - listen closely.

* Every compressor has it’s own sonic signature and ‘comfort zone’ (digital or analog) - although a serious unit can achieve many different sounds, it’s sonic signature will always be present to some degree and will become more obvious as the ratio parameter is increased. This can be heard when comparing the three different AFX models (Studio, Pedal, & Multi-band comps).

Clean Solo sounds: Use Them!

We all love the soaring, sustained sound of a smoothly overdriven guitar solo, but why stop there? We can achieve similar sustain for soloing without resorting to overdriven tones by using musical compression with a nice stereo delay or long reverb, with very expressive results. IMHO, the key is making the compression as smooth as possible (fast Attack/1.0 Look-Ahead/Filter 500z), and playing with a more connected, legato style. The setting of the noise gate becomes a bit more critical to avoid cutting off the ends of sustained notes.

EQ Tips

If boosting highs, I generally like to do it before the compression for better noise specs and a more dramatic effect. When boosting lows, I always do it after the compression so as to avoid the excessive pumping caused by slamming lows into compression circuitry - an exception to this rule would be if you use the Filter, set to a higher frequency than the pre-EQd lows, thereby minimizing their effect within the compressor’s detection circuitry.

Compressing a Bass

As a general rule, Bass compression should have a fairly low Ratio setting and not be ‘squashed to death’. It should also have a slower Attack setting since low notes take longer to ‘develop’. I tend to favor RMS detection with Soft-Knee for Bass.

In Closing

Compression is a wonderful thing - I like it so much that I only use one or two patches without some form of it! It can make rhythm parts more punchy & even, it can add extra sustain & smoothness to an overdriven sound, and it can give a lifeless instrument new urgency and fulness. Learning how to use it effectively within the AFX has become much easier with 9.02, and if you haven’t updated yet, I highly recommend it!


Cheers to All,

~Radley~
 
Thanks Radley! There is some great information here...even for the experienced user. This is the kind of stuff that makes this a great forum!!!
 
Nice post! I have one question about the MBC though...I read a post a while back that described using the MBC to make a bass patch by setting the 1st freq band at around 100hz, and the second at around 500hz - the lowest setting on my second band is 1000hz - is there a way to readjust that setting? or did I miss something...Rick
 
Now this is one fantastic essay. Right up there with the best !

Did you by any chance come across good Limiter settings in the Axe ? I'm fine with 'normal' compression and already had some pretty good results (I'm sure your examples will definitely improve these though), but as a Limiter I couldn't really dial the Axe's Compressor in yet.
 
:shock:
wow- excellent. Thank you for your time, knowledge and post. Very useful stuff.
Cant wait to dig in and learn some things.
 
wow great article Radley, while I have a basic understanding of compression, I always seem to struggle when applying and tweaking. Good to see you over here as I'm coming from the Boss GT forums as well and always found your contributions very revealing and educational. When I get my axe in a few weeks, I will definately be reading this article in more detail....

But thanks again for all the time and effort....much appreciated. ;)
 
carterpiano said:
Nice post! I have one question about the MBC though...I read a post a while back that described using the MBC to make a bass patch by setting the 1st freq band at around 100hz, and the second at around 500hz - the lowest setting on my second band is 1000hz - is there a way to readjust that setting? or did I miss something...Rick

Rick,

I have the same limit here (9.03) - my guess is that the OP got it wrong, but I guess it's possible Cliff has modified the frequency limits since that was posted? I will likely have more to say about the MBC once the new features have been added.
 
VegaBaby said:
Now this is one fantastic essay. Right up there with the best !

Did you by any chance come across good Limiter settings in the Axe ? I'm fine with 'normal' compression and already had some pretty good results (I'm sure your examples will definitely improve these though), but as a Limiter I couldn't really dial the Axe's Compressor in yet.

Vega,

Try using the Studio model set for very fast Attack (10) & Release (10) times, and setting the Ratio to 10:1 or higher, with Look-Ahead set to .750

Now, set the Threshold where it is only hitting the highest transient peaks - this is some pretty fast/severe limiting, and should be sufficiently transparent.
 
Great stuff! Added to the How-Tos page.

Thank you Radley for your efforts.

One more difference between the Pedal and Studio compressor type: the Studio takes up a lot more CPU-cycles than the Pedal. Good to know when you're running out of CPU %.
 
Thanks for your time and effort on this Radley!

Your compressor tips are going to find their way into my patches along side your PEQ and Reverb techniques. Really breaths some life and urgency into my tracks.

I can't believe how I glossed over the mix control on the compressor. For years I've mixed using the "New York Stlye" of having a parallel compressor on a separate bus then mixing it together with the uncompressed bus. Keeps all the dynamics of the quieter sections intact and then brings in the compression for the hot bits.

The mix control on the AFX can be set to do the same thing. In the box! Incredible!

Every time I think I'm getting deep with the AFX capabilities, someone reminds me that I'm barely scratching the surface.

Thanks again for sharing your expertise and your time with us!
 
Radley said:
VegaBaby said:
Now this is one fantastic essay. Right up there with the best !

Did you by any chance come across good Limiter settings in the Axe ? I'm fine with 'normal' compression and already had some pretty good results (I'm sure your examples will definitely improve these though), but as a Limiter I couldn't really dial the Axe's Compressor in yet.

Vega,

Try using the Studio model set for very fast Attack (10) & Release (10) times, and setting the Ratio to 10:1 or higher, with Look-Ahead set to .750

Now, set the Threshold where it is only hitting the highest transient peaks - this is some pretty fast/severe limiting, and should be sufficiently transparent.
Thanks for the tip, Radley. I'll give it a try !
 
Wow :shock:

I can't wait to read through this about 8 times and try it all myself. Thanks for all your work Radley! Your tips along the way have greatly helped me hone in on my dream sounds, and this compression article is definately going to close the gap even more. I know I have to re-do all my compression settings when I upgrade to 9.03, so I look forward to diving into it now that I have your guidebook.

Thanks!

D
 
Back
Top Bottom