When putting together a pedal board or mix chain, people often ask "where do I put the compressor?"  While there are no set rules about it, proper placement can have significant impacts and may be the secret to helping you get the sound you're after.

The first issue to consider is dynamics.  Devices like compressors/limiters, distortions, overdrives, boosts, gates, and dynamic filters and EQ's respond to dynamics.  Devices like delays, reverbs, choruses, flangers, phasers, wahs, and static filters and EQ's do not.  If you place a dynamic device before a non-dynamic device, the non-dynamic device will perform exactly the same.  However, if you place a non-dynamic device before a dynamic device, the dynamic device will perform differently.  Furthermore, if you place a dynamic device before another dynamic device, the second dynamic device will perform differently.

A good example of this is a wah pedal.  If you place a wah pedal before a distortion, the distortion will sound differently based on the position of the wah.  The wah's peak frequencies are actually causing the diodes, transistors, and/or mosfets within the distortion to clip at different amounts and frequency points.

The second issue to consider is noise.  Compressors, limiters, and distortions as a rule lessen the difference between the loudest and quietest signals.  They bring down the sound of the loudest signal and then you bring it back up with makeup gain, bringing the noise up with it.

Back to the original question of "where do I put the compressor?", here is a little cheat sheet that can help you decide for yourself depending on what you're trying to achieve:

• Compression before distortion will cause the distortion to react more or less to transients or pick attacks, depending on how you set the compressor.  Compression after distortion can smoothe out the light distortion, although it only serves to bring up noise when used with heavy distortion.
• Compression after overdrives and boosts will diminish their effect on the amp.
• Compression before gating will make it more difficult for the gate to tell the difference between audio and noise but will lower the noise that is created by the compressor itself.  If you can place the gate's detector circuit before the compression and its gate circuit after, such as with sidechaining or a few pedals that offer this capability, this is the best possible solution.
• Compression before dynamic filters and EQ's will cause them to respond less.
• Compression after static filters and EQ's will cause the compressor to respond differently than if it is before them.
• Compression after delays and reverbs will make their trails louder.
• Compression after choruses, flangers, phasers, and wahs will only increase noise.