# What is with compressors??



## sproul07 (Jun 23, 2007)

I have noticed an issue with compressors or any boost pedal that I have used. My main lead pedals are either a Big Muff or a Tube Driver and I always have something not only to boost them but to also function as an EQ for them. Right now I am using a Barber Tone Press but I have gone through many others, (vintage TS-808, DynaComp, RC Booster, Keeley Compressor etc). They always, ALWAYS buzz and hum like crazy when they're on with on the lead pedals, but are quiet when just used alone or with some modulation. Humbuckers and single coils. Can anyone explain to me why they do this and if there is anything that can be done about it??


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## devil6 (Feb 24, 2006)

From another Site:



> • Overdrive, distortion, and fuzz compress your signal already, so additional compression is often unnecessary, and may even interfere with the tone of the distorted signal. So you may want to place the compressor before the distortion, or switch the compression off while using distortion.



I run my compressor(Demeter Compulator) before my distortion and haven't experienced any problems


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## a Pack of Wolves (Sep 5, 2007)

comp B4 overdrive will be way quieter

like using an e.q. as a boost,
do it before o.d./dist/fuzz and it'll be way cleaner than after them


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## sproul07 (Jun 23, 2007)

Ya that is where I run it. My guitar goes into a Fulltone Wah into the compressor then into fuzzes and OD's then onto modulations and delays.


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## mhammer (Nov 30, 2007)

The "prime directive" for compressors is: As the signal declines, turn the gain up. problem is, very few stompbox compressors (if any at all) can tell the difference between residual hiss/hum and simply picking softly. So, when you stop playing, it treats the hiss/hum like a soft passage that desparately needs to be boosted.

Okay, put that on hold.

Distortions function by providing enough gain to yield distortion through some means. That could be via clipping diodes, but there are other ways too. Whatever way they achieve signal quality-change, though, the vast majority of distortion pedals WILL generate audible noise at the output. the noise might come from the circuit components or properties, or it could come from poor shielding, but it could also come from simply taking the teensy amount of hiss included in the input signal and multiplying that by a factor of 200 or more (common gain factors in many pedals). Hell, the Proco Rat applies a gain of over 2000 to frequency content over 1500hz.

So, if a distortion pedal is plugged into a compressor, the compressor will take the residual hiss from the distortion and crank up the gain on it, such that ssssssss becomes SSSSSHHHHHHHHHH!!!. If the compressor is plugged into the distortion, and you stop playing, the compressor takes the residual input noise and turns ssssss into ssssssss, then the distortion takes THAT and multiplies it by a few hundred to turn it into *SSSSSSSS*.

In contrast, other pedals like chorus, flanger, phaser, EQ, autowah, apply less gain than either compressor or distortion, such that the hiss is not increased in amplitude.

Can you "cure" this? To some extent, yes. 

First, it is wise to apply less than maximum compression. You shouldn't be depending on it quite so much anyways.

Second, it is wise to apply less than maximum distortion, since feeding a loud compressed partly distorted signal to most amps will incur additional distortion from the amp itself, sometimes of a higher quality tone-wise, and setting the pedal for less than max distortion means less than max gain and less than max hiss as a consequence. 

Third, you CAN often replace certain select components in both the compressor and or distortion with other components that will generate slightly less noise. A quieter output from a compressor multiplied by 200x is still quieter. As low-noise components become cheaper and cheaper, it becomes more and more difficult to find anywhere in the pedal to improve, but to the extent that you CAN find weak spots, a couple bucks thrown at parts can make a useful difference

Fourth, though maybe first, you should always strive to have the cleanest quietest signal possible hitting your compressor in the first place. Maybe its time to reconsider your pickups or shielding in the guitar or even cable quality.

Fifth, many electronic devices are designed with more bandwidth than they really need, simply because the manufacturer has no idea what you will be using them with. It may well be possible to trim some of the unneeded treble from the pedal and reduce audible hiss. Conversely, there may be all kinds of bass capacity you don't need and 60hz hum rejection could be improved upon a little too by changing a few parts.

Sixth, some *light* noise suppression in between compressor and distortion can be very helpful. Too many people use noise gates and noise filters only at the very end of the signal chain. While superficially there is some wisdom in that, the problem is that at that point they are attempting to cure too many accumulated noise ills at once and they have to use the gate/filter in such a heavy-handed way that it imposes a certain artificiality on your sound and can also behave in a counter-productive way. It may be far better to insert a noise-control device between compressor and distortion, where the noise levels will still be modest, and set it for long decay and modest threshold level so that it interferes with natural tone very little. My experience tells me that two noise gates, one near the start, and one near the end, set in a manner appropriate to their position in the signal chain, can do a far better job in a less invasive manner than one gate set to "brickwall".


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## FetusFajitas (Dec 16, 2006)

its true that putting compression before distortion will be quieter overall, but it wont sound the same as if you were to put it after.
i find when i put comp before distortion i can barely even notice a difference than if i didnt even have one there.


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## Hamm Guitars (Jan 12, 2007)

mhammer said:


> The "prime directive" for compressors is: As the signal declines, turn the gain up. problem is, very few stompbox compressors (if any at all) can tell the difference between residual hiss/hum and simply picking softly. So, when you stop playing, it treats the hiss/hum like a soft passage that desparately needs to be boosted.


What you are describing here is an expander. A compressor reduces the gain when the signal goes over a set threshold. Some units have a compressor and an expander, but I've only seen those in rack mount units - that's not to say that they don't exist in stomp box format.

The only way I can see a compressor causing a raised noise floor is through either using way to low of a threshold or bad gain structure. If you turn the threshold way down and compress the snot out of the signal then the guitar signal will not increase no matter how hard you drive into it. Driving more gain before the compressor will increase the noise floor, and since the guitar signal is 'choked' in relation to this noise, your signal to noise ratio gets pretty bad.

Putting the compressor earlier in the signal chain may very well solve the issue, because you are effectively reducing the level of the signal fed into it. If you want your compressor at the end of your signal chain then you might try setting the threshold at its highest level and easing off on the ratio, or reduce the gain of the signal comming into it and using the output of the compressor to get the level where you want it at the input of your amp. The downside of doing this is that if you turn off the compressor, your volume will drop.

Compressors are probably one of the most difficult devices that you can insert into an audio chain to get a handle on. Generally it is used very lightly - unless you are using it to change the dynamic envolope of a sound (-play notes backwards etc). They are also the most frequently mis-used devices in an audio system.


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## Guest (Dec 10, 2007)

FWIW I've got a HBE ComPressor Retro I'm looking to trade for a Barber Tone Press. It's dead quiet used before and after gain pedals. I've stacked it after two TS-9's ala Trey and there was no noticeable change in the noise floor when I wasn't playing. Currently I'm running it before my gain pedal and again: no noise. It's one of it's big selling points. PM if you're interested in talking a trade.


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## mhammer (Nov 30, 2007)

Hamm Guitars said:


> What you are describing here is an expander. A compressor reduces the gain when the signal goes over a set threshold. Some units have a compressor and an expander, but I've only seen those in rack mount units - that's not to say that they don't exist in stomp box format.
> 
> The only way I can see a compressor causing a raised noise floor is through either using way to low of a threshold or bad gain structure. If you turn the threshold way down and compress the snot out of the signal then the guitar signal will not increase no matter how hard you drive into it. Driving more gain before the compressor will increase the noise floor, and since the guitar signal is 'choked' in relation to this noise, your signal to noise ratio gets pretty bad.
> 
> Putting the compressor earlier in the signal chain may very well solve the issue, because you are effectively reducing the level of the signal fed into it. If you want your compressor at the end of your signal chain then you might try setting the threshold at its highest level and easing off on the ratio, or reduce the gain of the signal comming into it and using the output of the compressor to get the level where you want it at the input of your amp. The downside of doing this is that if you turn off the compressor, your volume will drop.


Don't confuse a limiter and a compressor. Yes, limiters *do* reduce gain for signals above a designated threshold, but the intent is to control peaks. Naturally, if the threshold is set low enough, one ends up with a sonic effect that is akin to compression, but compressors and limiters *do* differ.

Compressors aim for a constant volume level, and they do so by imposing high gain unless the circumstances call for less gain. When hotter input signals are amplified less and quieter ones amplified more, the net result is a fairly constant output signal level. (This is why they have the reputation for providing "sustain" though they do nothing of the sort, strictly speaking.) The down side is that the increase in gain is applied when the signal to noise ratio (hiss vs *real* signal) is at its worst, making any residual noise accompanying the input signal often uncomfortably audible. 

While rack-mount units may differ, cheap floor pedals do not really operate on any particular threshold principle. There is a *sort* of threshold at play insomuch as the diodes involved have absolute forward voltages, but compressors merely provide less gain as input signal goes up. I couldn't tell you whether the change in gain is linear or not since I imagine that would depend on the properties of the individual pedal. For example, the manner in which a control signal alters the resistance of a photocell may be different than what happens to a FET or an OTA or other gain/attenuation element. I haven't seen any digital pots in use yet (likely due to "zippering" effects in current 256-step devices) but I expect we will see them eventually in floor pedals. A recent peek at a schematic for the old MXR Dual Limiter indicates that clearly folks have been at least thinking about stepped attenuators as dynamic level-control elements for at least 25 years now.

Lest I create any misunderstanding, there are many instances where gain is fixed in a compressor, and level is varied. For instance, the Dan Armstrong Orange Squeezer came with a stock gain of x23. A FET-based attenuator just ahead of the gain stage would have the input signal attenuated by a control signal coming from the output of the gain stage. In the grand scheme of things, adjusting the gain applied to a signal, and adjusting the level of a signal fed to a fixed-gain stage, produce essentially identical results: the signal level is held roughly constant.

A major distinction between compressors and limiters is the source of the control/envelope signal. Generally speaking, compressors use feed*back* loops, while limiters use feed*forward* loops. Tracking the signal level at the input (feedforward) results in an envelope voltage that declines as the input declines, *irrespective* of what has been done to the signal after that. When the envelope is detected *after* the point in the circuit where level adjustment has taken place (whether by gain or attenuation), the behaviour of the circuit starts to be influenced by its own behaviour as much as by the input signal.

So, say the the circuit reduces the input signal by 3db. That 3db reduction now becomes part of the envelope signal that, in turn, results in an active 3db (or near enough) *increase* intended to keep volume level constant. The imposed increase, in turn, becomes part of the "new" envelope level detected. In this manner, compressors keep striving to self-regulate and maintain a stable level. In limiters, once the signal has been detected at the input, there is no active alteration of the input signal so as to alter the nature of the envelope level. There is only what the circuit does to adjust the level in response to the initial envelope. Not sure if that's clear or not, but the gist is that limiters will, all other things being equal, tend to outperform compressors in the noise department. It would also be a bit of a mistake to compare rackmount limiters with stompbox compressors.

As for expanders, there are different kinds: upward, downward and full-range expanders. Downward expanders (I've got a Behringer rackmount one, and there is downward expansion in the SSM2166-based compressor stompbox I made/have) DO reduce gain below some designated threshold as a means of reducing noise. Think of it as a way of increasing the contrast between soft passages and passages just a bit softer than that. Since the signal is not cut out completely, but rather merely reduced, one does not lose the attack and final tail of the signal as too often happens with noise gates. When downward expansion is married to level-dependent filtering (so-called "noise filters"), residual hiss can be made even less audible by trimming treble from the signal at the same time its absolute level is reduced. Since the decay-phase of a note tends to transition from fundamental plus harmonics to largely fundamental, trimming the treble at the dying gasps of a held note has minimal audible impact on "feel"; you hear the note but you on't throw tone out with the hiss.

Upward expansion, on the other hand, such as one might have found on the old Gibson RD Artist guitars, increases gain for signal above some designated threshold, such that the contrast between moderately loud and somewhat louder parts is enhanced. This tends not to have much impact on perceptible noise levels because it is a very short-lived action, being felt/heard mainly at the pick attack, when you are so inundated with the harmonic content of the string that most of us couldn't hear noise if it bit us on the nuts and drew blood.



> Compressors are probably one of the most difficult devices that you can insert into an audio chain to get a handle on. Generally it is used very lightly - unless you are using it to change the dynamic envolope of a sound (-play notes backwards etc). They are also the most frequently mis-used devices in an audio system.


Absolutely agreed on that one. In particular since it tends not to be an obvious "effect" to a great many ears unless the compression is dimed, far too many players use it exactly that way. Pity. And *then* they go and bitch about the noise.

FetusFajitas writes:


> its true that putting compression before distortion will be quieter overall, but it wont sound the same as if you were to put it after. i find when i put comp before distortion i can barely even notice a difference than if i didnt even have one there.


And that's because distortion pedals themselves impose a restriction on dynamics by virtue of their clipping action. Think of distortion pedals as "unclean limiters" that set a hard ceiling on how high the signal is allowed to go. This has several implications. One is that if you stick a compressor *after* a distortion, you will notice very little effect of the compressor because the amplitude envelope of the signal coming from the distortion is so smooth and steady that there is really no reason for the compressor to change the gain level. The exception to this would be a distortion pedal whose drive and output settings (and design) manage to preserve just enough of the guitar's dynamics that there is still something left to squeeze.

The other implication is that if you stick a compressor *before* a distortion and squish hard, the tone from the distortion will very VERY consistent and generally unresponsive to pick attack, since the input signal to the distortion will maintain the very same position, relative to the clipping threshold, pretty much all the time. That can be a good thing if your musical goal is to provide consistent tone (e.g., a slightly gritty rhythm guitar backing), but if the intent is to provide a solo tone with "feeling", too much squish before clipping will tend to get in the way of that.

As implied by much of Hammguitars post, the ideal strategy is to stay the hell away from "11" on the dial, and allow the effects to breath a bit by leaving some dynamic range in there for ALL the pedals. A bit of compression, a bit of overdrive, and a nice amp that responds to both can deliver the sweetest tones you've ever heard.


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## Hamm Guitars (Jan 12, 2007)

Perhaps they have simplified things a bit when it comes to stomp boxes and this may be what you are basing your info on, but a compressor is a limiter with a variable ratio - a limiter is a compressor with an infinate compression ratio above the threshold. They work on a threshold, whereby levels above that threshold are attenuated at the rate determined by the ratio. Program material that falls below that threshold is theoretically passed through unaltered - unless there is an element that is above the threshold - then the entire program material is subject to compression (including the program that is below the threshold at that time).

It is possible to create a digital compressor that would pass the portion of the program that is below the threshold unaltered and only compress the signal that is above the threshold, but I've never seen one myself.

Most compressors that I use have a control circuit that monitors the incomming signal and uses it to control a VCA. The input signal is split into two paths, one that is program and one that is the controll signal - provided you are not using the side chain function. Some have an expander that will increase the gain if the program level falls below a set threshold.

Like I said, guitar stomp boxes may work differently and may combine the compressor and expander into a single circuit, but that would be a compressor/expander, sometimes called a compander.


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## mhammer (Nov 30, 2007)

Admittedly, the boundaries between limiters and compressors are blurry. It certainly doesn't help that so many rackmount devices and VST plug-ins get called "limiter-compressor". And it also can be the case that the threshold at which limiting takes place (as well as the ratio employed) is such that there is absolutely not audible difference between that "limiting" action and what gets thought of as compression.

I should probably consult Tremaine's "Audio Cyclopedia" for a definitive answer, but here is how I have been led to understand it. "Peak limiting" is the process employed to set a ceiling on further amplitude of the signal. It has a long and glorious history of use in broadcast and recording facilities where the broadcast amplifier or vinyl cutting lathe or whatever was fine with any level below a certain maximum, but choked when the signal went too far above that point. In the case of sound reinforcement, peak limiting was what you used to save your speakers from having the cones rip the spiders right out of the frame in response to sudden transients. In all of these contexts, the explicit purpose of the peak limiter was to save the system from itself, whilst preserving as much of the original signal dynamics as possible.

Of course, because there could be no such thing as a _specific absolute threshold_ above which no signal should be permitted to increase, regardless of context or circumstance, limiters acquired variable thresholds so that the dynamic restriction could be applied in optimum fashion. When the threshold can be made low enough, the "dynamic transparency" of simply clipping the spiked Mohawks off of tall signals disappears, and *audible* dynamics are clearly affected.

Despite the capability of peak limiters to squish the bejeezus out of the signal, they still have their action imposed only on signals *above a given amplitude*. The action of compression, on the other hand, is intended to provide constant signal level for the *entire* range of possible amplitudes, with no real dividing point at which gain-alteration stops being applied. In the case of the classic MXR Dynacomp circuit, the nucleus of countless commercial designs from Boss, Way Huge, Pearl, Ibanez, Ross, et al., gain is constantly applied to the signal, and the rectified output of the gain cell (in this case a CA3080 OTA) is fed back so as to reduce the gain when the input signal amplitude increases. As is the case with anything that depends on diodes, there is a sort of unintentional "threshold" that the diodes' requirement for a minimum forward voltage creates, but the circuit is not deliberately intended to apply its all-systems-go-unless-otherwise-required to anything BUT the entire signal, from teeny-tiny to overload-level signals.

It is this very fundamental aspect of design that makes stompbox compressors so legendary as "noisy". Over on the DIY stompbox forum, it seems like every 2 months I have to explain to some kid who just got into pedal-building (and wants to sound like their idol by building a Ross compressor clone) that, no, their compressor is not malfunctioning and that the hiss is intrinsic to the design and functioning of simple compressors, and the hiss will go away if they use a hotter cleaner input signal and turn down the gain (where possible) of the compressor itself.

I real;ize a great many folks have grown up in the complete absence of this particular technology, but in the days of cheap mono cassestte recorders, they would often come with a built-in mic and an AGC/ALC/AVC (automatic gain/level/volume control). The cheap electret mics were often insufficiently protected against picking up motor noise, such that when you or the course lecturer you were trying to tape stopped talking, the gain would be increased again, and the motor noise would be cranked up. I built a couple of out-board lecture-recording mic units for my students to use that would plug into the external mic jack. Same cheesy-quality electret cartridges, but physically isolated from the mechanical noise of the recorder, and aided by a simple preamp circuit tailored to add a little edge to the speech and make S's, T's, K's and such a little more intelligible. This allowed the student to record at a lower sensitivity setting (lower record volume, implying less automatic compensation for low mic signal) and the difference between what they would get from the onboard mics and what they'd get from the outboard mic I provided them was staggering to say the least. Just about every ALC/AGC/AVC uses the same generic half-wave rectified control signal for adjusting gain. They are ALL "compressors" and they pretty much all sound crummy (well, except for the one that was used to record the rhythm gutar part for the Stones' "Street Fightin' Man").

I don't like to be critical, but the Fanshawe definition of limiting and compression as using different *ratios* of dynamic restriction (20:1 vs 10:1) strikes me as either misconveyed, mislearned, or worse, misunderstood by the instructor. Trust me, if I pick a threshold that only applies to the input signal maybe 1% of the time (i.e., the signal will only meet or fall above that threshold on rare peaks), the difference between a compression ratio of 2:1, 5:1, 10:1, or infinity will be barely audible under most listening conditions. In contrast if I apply a gain-reduction strategy to the entire signal range, differences of 2:1 vs 3:1 will be *quite* audible. So, ultimately, the perceptual consequence of the dynamic restriction will depend not only on how much you squeeze, but also how broadly that squeeze is applied across the entire range of possible signal amplitudes. Limiters CAN be made to sound similar, but when conforming to their original definitions they sound very different.

I posted an adapted version of the classic Armstrong Orange Squeezer that is intended to provide either peak limiting OR compression by selecting either feedforward or feedback control signals. I haven't tested it, but there is no ap priori reason anyone has been able to find yet why it wouldn't work. It would probably be quieter than the original too.

http://hammer.ampage.org/files/Tangerine_Peeler.gif



> Like I said, guitar stomp boxes may work differently and may combine the compressor and expander into a single circuit, but that would be a compressor/expander, sometimes called a compander.


Nah. Companders are used for encoding/decoding purposes, where the signal is treated one way at one point (input) and another way at a different point (output). The SSM2166 chip and its counterparts are intended to provide a blend of just about any dynamic control function, whether limiting, compression or some unnamed function. VERY smart and flexible chip. Take a gander at the appnotes and you'll be very impressed. Pity it isn't more widely available.

http://www.analog.com/UploadedFiles/Data_Sheets/SSM2166.pdf


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## Robboman (Oct 14, 2006)

*Noise Gate*

To the OP: just use a noise gate at the end of your pedal chain. When you mute the strings your amp is dead quiet. Done!

I've always used a comp at the beginning of my pedalboard chain and a gate at the end. First, minimize noise as much as you can, then dial in your noise gate so that it's threshold is just above the noise floor. Modern gates dont just cut your signal off instantly, they roll off gradually as the threshold is crossed. This is so it sounds more natural when you let a note sustain until it fades away.

What's a good noisegate pedal? No idea, I just use whatever is built in to the cheap digital multi-fx unit at the end of my chain (currently a Zoom G2). Some guys laugh when they see my board, it's got a nice vintage wah, analog comp and several boutique overdrives followed by that cheap plastic mass-market Zoom! But the gate works great, and its also my tuner, clean boost and eq. Sometimes I use it's delay and mod effects, (but never it's distortions.. they suck!)


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## mhammer (Nov 30, 2007)

Personally, I'm an advocate of using two noise-reduction devices, one at the start (or near to it) of the signal path and a second near the end.

The rationale is that guitar signals (as does everything, I suppose) have multiple sources of noise and "nonsignal" some, like hum, tend to be acquired early in the signal path, while others, like cumulative hiss, tend to snowball as you move from pedal to pedal along the patchcord highway.

The rather infamous reputation that noise-gates tend to have is because they are used at one point as a way of eliminating ALL sources of noise. Attempting to do that tends to require a very heavy-handed approach which in turn tends to impact on the "naturalness" of the signal and one's playing.

So, it is wise to have some gentle noise-reduction at the start of the signal path, and maybe curtail that hum when it isn't being amplified by that compressor and the distortion pedal or booster after it. "Head it off at the pass", so to speak, because once that initially modest hum gets amplified by subsequent pedals, you'll have to set the turn-on threshold of the gate so high that you'll lose beginnings and ends of notes.

In tandem with gentle hum-reduction at the start of the signal path would come noise-filtering just ahead of the amp itself. Noise-filtering is a kind of auto-wah that exploits the principle of auditory masking. When the signal is hotter, the filter "opens up" to allow the full spectrum through. Under those circumstances, the audibility of noise in the signal is reduced as the listener is essentially distracted by the musical signal. As the signal amplitude declines, the filter rolls off the highs. Happily, and if set up right, this is the point where a) the hiss now starts to be noticeable, and b) loss of treble content starts to be unnoticeable because the guitar string has "settled down" and is mostly fundamental without much harmonic content.

One of the problems that just about ANY noise-gate or noise-filter encounters is that as you progress along the signal path, there are more and more restraints on signal dynamics. Compressors steal dynamics. Distortion and overdrives steal dynamics. Phasers, and choruses with limited headroom steal dynamics, and so on. As the dynamic range gets more and more restricted, it becomes that much harder to identify the point or threshold at which action should be taken by any of these devices I like to classify as "signal hygiene" devices.

Consequently, it is advisable, though not always feasible, to feed one's gutar to an initial buffer stage that will detect the amplitude envelope of the signal, and feed THAT envelope, with all picking dynamics intact, to the sidechain input of any noise-reduction device inserted later on. In a perfect world, this would be something that has one send-return loop with noise reduction prior to send, and noise reduction after return. Guitar goes in. Loop sends a cleaned up signal to booster, compressor, etc., and what comes back to the station from your last pedal in line gets cleaned up again to eliminate the audio hash acquired over 4 or 8 or 12 pedals as the case may be. Though the rectified envelope signal would be the same, one ought to be able to adjust the sensitivity of each of the two complementary noise-control devices independently.


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## sproul07 (Jun 23, 2007)

Wow. Lots of great info. Thanks guys. Compressors are definatly the hardest pedal to work with


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## mhammer (Nov 30, 2007)

I wouldn't describe them as the *hardest* to work with, necessarily. However, I would agree with you that thinking about what the impact of dynamics is, rather than an in-your-face tonal change, can be hard for many musicians, and especially beginning guitarists. It's a bit like the difference between learning to cook with salt or chili peppers, and learning to cook with saffron. The one requires more insight into the _whole recipe_, and not just a single flavour.

Back in the day (late 70's), my "pedalboard" consisted of a Univox compressor, an Electro-Harmonix Hot Foot (that I would use to control the compressor output level), an MXR 6-band EQ, and MXR Envelope Filter, an MXR Noise Gate, and a small Vibratone/Leslie (though maybe something that comes after your amp shouldn't be thought of as "pedalboard"). One of the things I was able to do was to use my compressor to limit the dynamic fluctuation "just so", such that if I set the controls on my envelope filter just right, the filtering would essentially waffle rather than sweep in an overt way. I was able to nail some of the sounds Todd Rundgren was producing on guitar at that time. 

Another thing the judicious use of the compressor allowed me to do was achieve some pretty decent "tape-reverse" effects. I would set the envelope filter for slowest attack, and moderate sensitivity, feed it into the 6-band EQ, and set the EQ for full boost on the top 4 bands and full cut on the lower 2. The compressor would be set for moderate compression and reasonably hot output. The result was that the envelope filter would sweep fairly smoothly and a little slower from the low end (which was radically cut, remember) to the mids and above (which were boosted to the point of clipping when taking the full brunt of the compressor output). Much like real reverse-tape, the sound would go from much softer and less bright, to much louder and containing more harmonics. Fundamentally, it was the compressor that allowed me to do it.

My sense is that too many guitarists have been led to have a too simplistic conception of what compressors are and do, and this limits their creative thinking and tonal options. Compressors CAN be very friendly devices, but the first step in them becoming so is understanding how they work.


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