Extensive compressor reviews and FAQ

How to choose and set up a rack full of gear:
I recently got an email asking for a basic tutorial for beginners on how to put together a rack rig, which gear is needed, and what you'll need to know. So here is my first stab at it; I will undoubtedly edit and add to this page over time.
Rack case
Power amp (opens a new page)
Power conditioner (opens a new page)
Equalizer (EQ)
Noise reduction
Half-rack units and shelves
Order to arrange items in rack
First, my general rule of thumb for buying rack gear is "if you aren't sure you need it, you DON'T need it." At least once a week I see someone say they have an extra empty rack space and they want to know what to put in it. Don't put anything in it! You'd just be adding to the weight of your rig, and adding to the number of things that can fail or cause problems. Instead, think of the empty space as ventilation, to help keep your amp from overheating; or get a smaller rack case. People say they heard that everyone uses a power conditioner, or a compressor or whatever, so they want to know which one to buy. But first, not everyone really does use those items; and second, these are just tools to solve specific problems. If you don't have the problem, or if you don't know one way or the other, you probably don't need the tool to solve it. Even if you just want to protect against a future problem, the fact is the tool may not do any good unless you actually understand how it works. A compressor may not necessarily prevent blown speakers, and a power conditioner may not necessarily protect your amp from "bad power", the same way your car won't automatically prevent itself from crashing in traffic.
Also, think about size and weight. An eight-space rack full of gear can easily weigh 100 lbs (45 kg) or more. If you're a young macho guy, or a touring star with roadies, this is no problem--but for the rest of us, lugging a giant 100 lb cube up and down a flight of stairs can be difficult and injurious. So keep your rig as simple as possible. And remember that for any piece of gear you're considering, there may be a smaller, lighter alternative.
The flip side of everything I just said is "if you want it, who cares whether you need it". You're probably buying musical gear for your own enjoyment, not to feed the hungry people of the world. And that's fine, there are many worse things you could be doing with your money. So assuming you are going to buy some gear and arrange it in a rack, here are some suggestions:
First there's the rack itself. Unfortunately there are none I recommend to suit everyone--all of them involve compromises in terms of durability, weight, or how they fit your gear, so that you have to decide for your own situation which aspects to sacrifice. For example the typical plastic cases are light and inexpensive, but bulky and prone to cracking. The roto-molded ones are much tougher, but also bulkier, and their interior protrusions interfere with fitting some gear. Plywood cases are more rugged and less bulky, but they usually weigh a lot more. The shock-mounted cases are tempting for their extra protection of sensitive gear, but the ones with springs are huge, and the ones with foam may cause amps to overheat. So pick which compromises are most acceptable to you. My favorite racks for around-town use are custom-made from 1/4" plywood with a plastic exterior laminate, and aluminum parts protecting the edges and corners. The main thing I will suggest for everyone is to get a rack that is not too deep front-to-back. If all your gear is like 5 to 11 inches deep, a 20" deep case adds a lot of extra bulk and weight without any benefit to you. Rack cases are listed by the "rack unit" (RU), which is 1.75" of internal height; so for example a 6RU case has 10.5" of vertical interior, and an amp that is 3.5" tall fits in 2RU.
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Click here to read about power amps. The most important thing to look for is whether the power amp has an appropriate input sensitivity for your preamp. Look in the amp's specs list for low input sensitivity ratings like 0.7 V to 1 V, and avoid high ratings like 1.4 V, unless you are sure your preamp has very high output levels. Stick to the big reliable brands; the cheapest power amps, often sold as DJ gear, are just not dependable--and they often lie about their wattage output.
Click here to read about power conditioners. The short version is that you probably don't need one, but they can be useful if you get one whose actual abilities match up with a specific power problem to be solved.
Regarding compressors, well, you found this page via my compressor reviews and FAQ. Be sure to read
this article about whether you need a compressor. My "top picks" page has a section listing the rackmount units I recommend.
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How about EQ? If your racked amp or preamp doesn't have much EQ control, then maybe you would benefit from adding a more versatile rack unit. However, a lot of modern preamps already include decent EQ features like sweepable mids, or five bands of EQ, that honestly do more practical good for your on-stage tone shaping than any 15 or 31-band graphic EQ would do. Each added band of EQ is an extra opportunity to mess up the sound--partly because of phase alterations to the signal that potentially smear or muddy your tone, and partly because you may not know what exactly needs to be adjusted. With EQ, "more" is not "better". Of course it's a balancing act because if you only have a 3-band EQ then your control options may be too limited. Also remember that in most cases the EQ in your rig is just for you to hear, not the audience, because the audience will mostly hear the PA and its EQ. If a soundman sees a complicated EQ in your rack, he will usually scowl and insist on taking a DI signal from before the rack, leaving that EQ out of his mix. So really consider whether any benefit to your onstage tone, just for you, is worth carrying the extra EQ unit around.
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Rack tuners have nearly gone extinct. Most have been discontinued by the manufacturers, and you will rarely see one used onstage anymore. Even though it might look cool to have a bunch of flashing lights in your rack, and even though a large display up off the floor is easier to read, the fact is that nowadays good tuners can be so small, and so inexpensive, that almost nobody thinks a rack one is worth its bulk and weight. A clip-on tuner is easy to read, and a pedal tuner can be used as a convenient mute switch.
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"Maximizers" and "exciters" are supposed to magically make everything sound better, but too often the actual result is shrill boosted highs, boomy boosted lows, and scooped-out mids. The "enhance" on the Boss LMB-3 is just a mid-scooping EQ like that. The BBE Sonic Maximizer does the same thing, but it additionally splits the signal into high, mid, and low bands, adding an almost imperceptible amount of delay to the mids, and slightly more delay to the lows. This is intended to counteract an opposite phase effect that BBE says is created by your speakers. The Aphex Aural Exciter applies a tiny amount of delay to the highs, and compression on the lows. Turning up the "Big Bottom" knob boosts the lows into that compression, for a perception of louder lows without turning up the peak levels. Some exciter-type devices also increase the harmonic content of the high end, really a type of light distortion, to add an "edge" or "sparkle" to the highs. In all cases, the important thing is to use only a little, keep the knobs at low settings. The more you turn them up, the more fake, harsh, and scooped your sound becomes. If you like what these units do for your tone at low settings, then by all means use one for your onstage rig. It is meant to go last in the chain, after any other signal processors, right before the power amp. Don't bother sending that processed sound to the PA, because the EQ and crossovers of the PA rig will essentially undo any phase benefit from the maximizer. In my personal opinion, these gadgets can help a cheap or small amp sound better, but in general they don't do enough good to be worth lugging around.
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Noise gates are almost never the right choice for solving noise problems. Whether there's hiss from your rig now, or whether you are still planning out your rack rig, there is almost always a better way to reduce noise than to use a gate. You may be tempted to buy a particular rack compressor because it includes a noise gate, but that is not a good plan. Read this article. Although I don't like to recommend any noise gate, the very best-functioning one I have tried was a (discontinued) Ashly SG-series unit that included controls over attack, ratio, and other parameters.
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The question of whether to use racked multi-effects, and where to put them in your rig, is a bit tricky. Multi-fx offer a lot of processing power in a convenient package, but they have limited options for external routing or combining with other devices. Also, in one multi you may like some of its effects but not others--for example the reverbs and delays in multi-fx tend to be quite good, while the overdrives and distortions tend to be disappointing. This is a big part of why pedals are so popular right now, they are easy to mix and match to taste. A rack fx unit will almost always go between your preamp and the power amp, or in the fx loop of an amp head, using regular unbalanced (guitar) patch cords. It only gets complicated when you mix pedals and rack units, or when you listen to guitarists who insist that there is a particular order that effects have to go. Be sure to read the articles in my FAQ about the order of the fx chain, pedals versus rack units, and line level vs. instrument level. Another issue crops up when you want to use the stereo outputs of a rack effect but you don't have a stereo amp rig; the only answers that make any sense are either: (a) get a second amp and cabinet for a true stereo rig, or (b) forget the stereo outputs and just run your effects in mono. For most people the idea of buying a second amp and cab (and lugging it all to a gig) is too costly to be worth the "coolness" of stereo effects.
Which effects unit should you buy? They are all just colors in the great big crayon box of sonic possibilities. Some look great individually but ugly when mixed together; some mix well with one or two specific other colors, but not with the rest; and some are boring by themselves, and only become valuable when paired with other colors. Experiment, have fun--and don't forget the beauty of simple minimalism as well.
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There are some effects and preamps in a small "half rack" or "1/3 rack" format, and these can be very tempting because it seems like you could mix and match more different processors in a rack this way. Several of my personal favorite preamps and compressors are in this format. The problem is in mounting them on a shelf so they actually fit into 1RU. The shelf itself, plus the thickness of two pieces of Velcro, or foam double-sided tape, or the heads of screws, can add enough to the overall height that it won't fit into a 1.75" space, at least not without badly scratching up your other rack gear. The best case scenario is mounting multiple items from one manufacturer together, using their own proprietary racking system. For example you can buy a special shelf or rack frame to mount two Summit devices side by side, or two by FMR, two by Boss, etc. But just try to mount an FMR next to a Summit--it's a nightmare. I've been struggling with this dilemma for over twenty years. Yes it can be done, but no it won't be easy or pretty. The one lucky break is if you have a plastic rack case, they may have a little extra airspace above the top rack-unit space, and below the bottom one, so you can sometimes fit a too-thick shelf of half-rack units in the top or bottom slots.
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Keep the cables in your rack short, to avoid tangled clutter and avoid picking up excess noise. I prefer to make them as short as possible, like two or three feet, but up to 6' (2 meters) is OK. Color-coding your cables, with colorful tape or shrink tubing, can help minimize confusion. The two common cable types are balanced and unbalanced. Unbalanced cables are just regular guitar cords. Balanced cables are usually mic cords, with XLR plugs, but there are also balanced cables with 1/4" TRS plugs. You can tell them apart from guitar cords because the TRS plugs have two carved-out stripes near the tip, while a regular guitar cable plug has only one stripe. You'll need to read the manual for each piece of gear to determine which type of connection it can use. Just using a balanced cable will not make the gear inputs or outputs balanced! Usually the benefit and point of balanced cabling is that it rejects noise; but even unbalanced cables, in the very short lengths we're talking about, will not pick up too much noise. So in most cases you won't gain anything by using balanced connections among the few items in your rack. The one exception is the step going right into the power amp, where in some cases the amp can see a 6 dB stronger signal at the balanced input. Read the manual for your power amp to find out whether this is the case for you, by checking the spec page to see if it lists different sensitivity or gain specs for balanced versus unbalanced inputs.
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What order should you connect everything together? Usually it will be simple: preamp "line out" to the input of the next piece of rack gear; the output of that processor connects to the input of the next one; and then the output of the last processor in the chain goes to the input of the power amp. If you are using an amp head with an fx loop, then the loop "send" jack is the preamp output, and the "return" jack is the power amp input. In the fx chain generally you'd want your dynamically-responsive effects first (overdrive, envelope filter), then the rest in whatever order sounds good to you. Read this FAQ article about whether EQ goes before or after compression. Pay attention to the input and output levels of each unit, as they make a huge difference in how the whole setup sounds and operates.
What order should they be racked up, top to bottom? First consider weight and depth: the largest, heaviest items go on the bottom, and the smallest items go on top, to keep the rack from tipping over and falling off a table or stand. Next you can organize the units by the heat they produce, and whether they have heat vents or fans on the top or sides of the housing. Heat rises, and vents must be unobstructed. If you put a digital fx processor, for example, immediately above a unit that gets very hot, the heat could harm the digital unit or cause it to malfunction. Also some digital devices run very hot themselves! So if you happen to notice heat coming off any item in the rack, you can either leave an empty space above it for ventilation, or move it to the top of the rack. This is MOST important with the amplifier itself; some people's amps have actually caught fire onstage when their fans or vents were blocked.
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