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**OnlineStageGear** · 04-20-2003, 10:42 PM

Re: what the hell is compression?

Think of it like evening out your sound.

Matt

**Lev** · 04-20-2003, 10:56 PM

Re: what the hell is compression?

I think it cuts off the peak of the sound waves, limits the amplitude. I could be thinking of a limiter though [img]graemlins/scratchhead.gif[/img]

**Cleveland Metal** · 04-20-2003, 11:00 PM

Re: what the hell is compression?

Read this maybe...

http://www.guitarnoise.com/sound/20020510.html

Otherwise....

A compressor is used to reduce variation in the loudness of a signal. By setting a threshold level, the compressor will attempt to maintain that level, even when the input varies in amplitude. Bascially, weak signals get boosted to the threshold and all of the strong signals get attenuated to the threshold.

For a guitar, compression will give you more sustainfor notes, and more sensitivity. But, you'll lose dynamics (variations in the volume) in your playing, and they'll add noise since if the signal is too low, it will find hum and buzz and amplify it.

[ April 20, 2003, 11:07 PM: Message edited by: Cleveland Metal ]

**JacksonJuiceBox** · 04-21-2003, 12:32 AM

Re: what the hell is compression?

Really simple way to put it, you can get tthe same sustain you have when your saturated in distorsion in a clean tone.

**Cleveland Metal** · 04-21-2003, 01:14 AM

Re: what the hell is compression?

[img]graemlins/scratchhead.gif[/img] I wouldn't quite say that...

**11miles** · 04-21-2003, 05:49 AM

Re: what the hell is compression?

Cleveland, you gave us a lot of material to read!
:-)

And since i got to know the compressor a little bit i was wondering how a maximizer works in oppose to a compressor?

**Matt Crooks** · 04-21-2003, 08:51 AM

Re: what the hell is compression?

One thing to keep in mind, a compressor does not make your signal louder. It actually limits the amount of volume increase past the set threshold level. By evening out the signal level, you can then turn up the makeup gain on the compressor (think of it as the output knob) which gives you a louder signal. However, it is the output of the unit boosting the signal (just like any box that has an output knob) not the act of compression that is making the signal louder. An expander does make the signal louder - any signal that falls below the set threshold is boosted. However, I've yet to see an expander used effectively for guitar.

A maximizer is not a compressor/limiter/expander it is a tone shaping tool. By taking the input signal and adding in selected out of phase signals with the original source it gives the source more percieved bass or treble depending on the unit and settings.

Another thing to think about when using compressors is that distortion is basically a type of compression - just extreme compression. With a distortion unit (or preamp) the threshold of the compressor is very low, so any signal will cause the unit to clip, which is what causes the distorion (the clipping of the waveforms). Different preamps and distortion units clip the signal differently which is why different unit sound they way they do. That being said, adding a compressor before your distortion can rob you of a good deal of gain, unless you crank the makeup gain on the compressor, and then you're really using the compressor as a boost (which as tube creamer does better) not as a compressor. For clean sounds a compressor can be helpful in leveling our the sound so that you do't have huge jumps in volume between the bass strings and the treble strings. It can also be good in getting that nice '80s punch clean sound.

If you want a good compressor, for not a lot of cash, look at the RNC from Mercenary Audio: http://www.mercenary.com

- Matt

**rodrigo_echeverri** · 04-21-2003, 03:04 PM

Re: what the hell is compression?

Matt and John, thanks!.. nice and clean. I have done my homework now and understand.

11miles: you are European, I am sure you guys can read better than us americans (or canadians).. [img]images/icons/smile.gif[/img]

The maximizer concept is a bit complex. In terms of signal, the compressor and the equalizer affect the magnitudes of the waves but the Maximizer only messes up with the phase.

Look at this (don't click, copy ans paste on your browser's URL):

http://www.geocities.com/rodrigo_ech...ompression.jpg

There you can see a signal as a solid line. That system has a lower and an upper limit. These limits are very important in signal processing because they are given by "real" conditions of your system. Usually anything beyond these limits will get distorted (analog system) or clipped (digital).

The dotted line shows the signal after having applied compression to it. The original solid line signal has been attenuated around the peaks that surpass the limits of the system. Usually you tell your compressor how much is your limit by setting something called "treshold". The compressor "detects" when your signal is going out of bounds and then scales it down to avoid it. The amount by which the compressor acts on the signal is given by the "compression ratio". The more compression, the harder your signal is puched towards the limits.

A limiter is a VERY strong compressor, which will try to keep the signal within bounds at all costs.

questions:

[email protected]

**Ace** · 04-21-2003, 10:45 PM

Re: what the hell is compression?

Most popular compressors, such as the dbx 166 and 266 come with a built in noise gate, that will completely cut off the signal once it drops below a certain dB, thereby making your amp pretty much "dead sounding" once you stop playing, as opposed to amplifying noise in your signal chain. This threshold is set independently of the compression threshold. Also you have more controls for attack and decay, but basically it works like this:

You pick up your guitar = the noise gate cuts all the low level noise from your strap banging your guitar and the guitar hitting your belt, etc...

You hit a loud chord = the noise gate opens up and permits the entire signal through to the point that the volume hits the compressor threshold, which limits any signal over the threshold, evening out your tone.

You hold the chord = the compressor amplifies the signal as it gets weaker, giving you more loud, even sustain.

The chord dies = once the volume reaches the noise gate threshold the noise gate completely cuts the signal back down to zero.

The overall effect is what could be called "evening out your volume" or I've heard it refered to as "squashing" for some reason. It is easiest to explain with a graph. Hope ths helps!!

**Matt Crooks** · 04-22-2003, 07:52 AM

Re: what the hell is compression?

Ace:

Not quite...

You pick up your guitar = the noise gate cuts all the low level noise from your strap banging your guitar and the guitar hitting your belt, etc...

This is true, as long as all of that noise is below the threshold of the noise gate.

You hit a loud chord = the noise gate opens up and permits the entire signal through to the point that the volume hits the compressor threshold, which limits any signal over the threshold, evening out your tone.

This causes the noise gate to open, it also exceeds the threshold of the compressor which compresses (or squashes) the volume of the signal. This will decrease the overall volume of the guitar (it does not even out tone).

You hold the chord = the compressor amplifies the signal as it gets weaker, giving you more loud, even sustain.

The compressor does not amplify the signal. As the signal gets weaker, the compressor compresses the signal less so that the volume drop off is not as great.

The chord dies = once the volume reaches the noise gate threshold the noise gate completely cuts the signal back down to zero.

This is true.

For the compressor think of it this way:

<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">Action Gtr Signal Output
------------- ---------- ------
Pick Up Gtr 10db 0db
Hit Chord 50db 40db
Sustain 40db 35db
Starts Fading 30db 30db
Fading 20db 20db
Faded out 10db 0db</pre><hr /></blockquote>The compressor is set with a threshold of 30db, with a 2:1 ratio. The noise gate is set with a threshold of 10db.

When you pick up the guitar the signal is still below the threshold of the noise gate, so it kills all signal.

When you hit the chord, it puts out a 50db signal. Because this is above the compressor threshold of 30db, anything above 30db, comes out at a 2:1 ratio. In this case the 50db is 20db above the threshold, so the compressor squashes that down to 10db above the threshold, resulting in a total of 40db.

When the chord sustains, it is putting out 40db. Again this is above the threshold so the compressor lets out 35db.

When the chord starts fading, it is at the threshold of the compressor, so the compressor does not compress the signal, so the total signal is 30db.

As the signal fades to 20db, it is still below the compressor threshold so the signal is 20db.

Once the signal fades to 10db, the noise gate cuts off all signal. Note that the chord may still be ringing, but because it is below the threshold of the noise gate, it is cut off.

If you look at the chart you will se that the uncompressed signal goes from 50->40->30->20->10, the compressed signal goes from 40->35->30->20. The result is that the compressed signal has a more even volume until the signal drops off. This allows you to turn the amp up louder without the fear of the super loud signal getting through. Notice, however, that the compressor never makes the signal louder, it only makes the signal softer and more consistent.

Also, if the ratio of the compressor was set higher than 2:1 (i.e. 10:1), you would see an even greater leveling of the signal.

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what the hell is compression?

what the hell is compression?

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