Compressor Effect Pedals

What’s The Difference In Compressors?

When the Compressor Pro came out many people thought that it was just an advancement of the old 4 Knob compressor into a bigger box with some controls added.  That couldn’t have been further from reality.  The Compressor Pro is a very different type of compression than the original Keeley Compressor.  So what’s the difference in Compressor Effect Pedals?  One is a compressor-limiter and the other is a compressor-expander.

With the new Compressor Plus coming out we want people to make an informed decision about which compressor they might want and if there might even be a very useful and powerful reason to have both on their boards.

Compressor Effect Pedals

Compressor Limiter

Compressor Pro White Face Keeley


Compressor limiters (Comp Pro or GC-2) can be used in a variety of places in the signal chain.  Since they don’t add lots of noise in the signal and they serve to limit peaks you can find them in mixing boards and recording consoles and a variety of places other than ‘first in your guitar path’.  We have found that lots of pros like to use the Keeley Limiting Amp (a simplified version of the Compressor Pro) at the end of their chain to make sure their volume stays within a certain limit and their entire rig has a polished sound.

Compressor Sustainer

Compressor Effect Pedal

2014 Keeley Compressor C4

Compressors with expanders or sustainer circuits like the old 2 or 4 knob and the new Compressor Plus have circuits that add sustain by increasing the gain as the notes decay.  As your notes fade out imagine there is a guy turning up the volume on your amp at just the right time to make it seem like your notes are ringing out longer!  The little magic engineer turns down the loud parts and turns up the low parts just about as fast as you can pick!

So there’s one difference in Compressor Effect Pedals, some add sustain some don’t.  Some have expanders and some don’t.  Ones that don’t have expanders have the tendency to be very quite, almost noise free like the Compressor Pro.  Others like the old 2 or 4 knob Keeley Compressors add more and more noise (when you’re not playing) as you increase the Sustain.

Compressor Effect vs. Compressor Tool

I like to think of the old Keeley Compressor Effect Pedals as just that; a compressor “effect”.  You can do great funk riffs with them.  Sounds just like the records.  You can do crazy sounding chicken-picken’ riffs and sound just like you’re favorite country star.  Those are compression effects.  Just like the “bloom” you hear on slide players recordings when they use a compressor (or two)!  It’s an effect.  Then, there’s the compression you hear on just about every recording that’s ever been made.  You don’t think of it as an effect but rather a studio tool to even things out and make things sound more polished.  It’s easier to listen to a recording that has a certain amount of compression to it.  The highs are brought down to make transitions easier to digest.

Can you use both?  Yes!  Most certainly.  There are many of our customers that use two compressors.  One for sustain and one for the end of their board to be the “pro-engineer” in their mix.

Back in the day when Harmony Central reviews were a great place to hear from customers…Keeley Compressor Review

Here’s a link to the very first Keeley Compressor page (back in the AOL days)!


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