Buying Guide:Keeley Compressor and 4-Knob Compressor

Studio-quality squeezeboxes for your pedalboard


By Buddy Lane, Contributor, Harmony Central


Mention compression pedals and any true gearhead will say “Keeley.” Robert Keeley has become the go-to man for clean, transparent, stompbox compression. Though he has expanded into modifying other company’s effects and creating other original pedals, the Keeley Compressor is where it all started. We had a chance to look at this classic, now with a few updates, as well as a newer model, with two additional knobs.


Squeeze me

Before we get into the pedals, a quick word about how compression works—something that can be confusing, even to professional musicians. Basically, a compressor is an automatic volume control that adjusts the gain level of the signal that is put through it. This means it can lower the attack level to keep the sound from distorting when recording, and/or raise the output level as the original signal dies to increase sustain. Guitarists use it to even out their performances and increase the ring of their notes; electric bassists might use compression to tame pops and slaps; while a keyboard player can keep LFO sweeps from getting out of hand. Occasionally employed for coloration, great compressors are generally preferred by musicians to deliver a clean, transparent signal. It is these qualities that have made Keeley’s reputation.


Parts ain’t parts

Robert Keeley based his compressor on the coveted Ross stompbox, but has refined it even further. To maintain true-bypass switching and still have an on/off light, he needed to use an expensive triple-pole, double-throw switch. His design ensures there are no ground loops. The controls and jacks are point-to-point wired. The output transistors are matched for gain within 1%. Keeley uses the Harris (Intersil) CA3080E to prevent noise and eliminate any tonal effect on the original.


The blue on/off LED employed on both pedals uses only 2.5mA of current. The overall circuit draws so little power that the company claims that a 9V battery should last four to six months, even with heavy usage.


Control issues

The two-knob and four-knob Keeley Compressor pedals are the same effect; the difference merely being that the Attack and Clipping controls now available on the inside of the two-knob unit have been moved to the outside for the four-knob model.


Attack determines how fast the compressor starts acting on the signal. If I want to hear the initial transients loud and clear when I hit the guitar strings with my pick, I set the Attack for slow (clockwise); if I want to squash that initial hit, I would set the knob for a fast attack time (counterclockwise). This doesn’t affect the sustain, which is controlled with the—you guessed it—Sustain knob.


The Clipping control (called Trim in earlier models) lets you set the input volume of the compressor. This way, if you have a Sustain and Attack setting that you like for your Stratocaster with single-coils, you can just lower the Clipping level when you plug in your humbucker-equipped Les Paul to maintain the same compression effect. Nice!


Sustain for days

I tested the two compressors with a single coil-equipped Stratocaster and a humbucker-equipped Jazzmaster into a Fender Blues Junior. The two-knob compressor was a colorful sea foam, while the four-knob version a more serious metallic silver with metal knobs.


On the two-knob model, the internal attack and clipping was set perfectly for my Strat. If I were to use this compressor regularly with a humbucker guitar, I might go under the hood to slow the decay and reduce the clipping level. But used with single coils, it squashed the initial attack just enough to even out my playing and make me sound better than I am. Or at least as good as I could be, tonally speaking.


With the Sustain up around two o’clock, chords seem to ring endlessly. Even wiggling the whammy bar, which can often kill sustain, was unable to dampen the chime.


Another way I like to use a stomp compressor is to run it into an overdrive pedal or a slightly distorted amp. This allows me to keep the gain low on the overdrive or amp while deriving my sustain from the clean compressor. I find that the notes cut through the band mix better using this approach. The Keeley was ideal for this, as it had virtually no effect on my guitar tone, sending the amp or overdrive the same frequencies as if I were plugged straight in.


The two-knob unit worked and sounded great for many applications, but as an inveterate tweaker I preferred the instant access to the additional parameters afforded by the four-knob model. For rock, I slowed the attack, letting me pile on gobs of sustain without squashing the initial strike; for imitation pedal steel licks and ambient work, I liked the volume swell effect of a fast attack.



Which Keeley Compressor you buy will depend on your penchant for regularly changing parameters. If you use compression for any or many purposes, you need only to check out either of these to discover why Keeley has become the stompbox compression standard. Whether you opt for the streamlined operation of the two-knob model or the one with tweakable Attack and Clipping controls, you will find dynamic excellence in these two Keeley compressors.


Check out two great solutions in guitar-based compression from Keeley. Order today from Musician’s Friend and get our 45-Day Total Satisfaction and Lowest Price Guarantees.