The serial number on the back of our review model Compressor Plus is 47061. But the digits don’t represent some cryptic in-house code. Oklahoma’s Robert Keeley Electronics has actually sold nearly 50,000 U.S.-made compressor pedals—a remarkable figure for an indie builder.

The latest iteration of Keeley’s squeezebox is the Compressor Plus, which replicates the tones of earlier Keeley models while adding several meaningful new features: a blend control, a post-compression tone circuit, and a single-coil/humbucker toggle. It runs on standard 9V power, and there’s a battery compartment.

That ’70s Squeeze
Like most of Keeley’s compressors, the Plus is based on the 1970s Ross Compressor, which was itself a near-clone of the earlier MXR Dyna-Comp. (Really. I’ve got schematics for the Ross and MXR right here, and the “two” circuits are very similar.) Both pedals had just two knobs (compression amount and volume), where many full-featured studio compressors enabled control of compression ratio, attack and release times, and more. The Compressor Plus remains a simple ’70s-style stompbox squeezer at heart. But it has some very nice new options.

The blend control is especially welcome. Players who use compression rely on the effect’s ability to even out note attacks and increase sustain, but there’s a downside: Note and chord attacks lose impact, and dynamic nuances can vanish. But with a wet/dry blend, you can have strong note attack and increased sustain.

With a wet/dry blend, you can have strong note attack
and increased sustain.

The new tone control addresses another common compressor issue. When note attacks are flattened, tones can seem darker. But here, you can add a bit of high-frequency shimmer to restore lost presence.

The final addition—the single-coil/humbucker toggle—is really just a primitive release-time control. Since humbuckers tend to put out more energy than single-coils, they can push your tones heavier into compression than single-coils, all other settings being equal. Keeley’s humbucker mode provides a shorter release time, so notes and chords rebound more quickly from compression. As a result, the humbucker setting is louder.

A Single or a Double?
There’s no reason you can’t use both release settings with both types of pickups, as heard in the demo clips that accompany the online version of this review. Clip 1 features the uncompressed sound of a guitar with humbucking TV Jones Filter’Tron pickups. Clip 2 is the same part through heavy compression at a 100 percent blend setting. For Clip 3, I’ve toggled over to single-coil mode, and as expected, the sound is a bit quieter and more dynamically flat.

Clip 4 adds the blend control at a 50/50 wet/dry mix. Big difference! While the compressor still flattens and sustains, the result is subtler and more naturalistic. For some players (well, for me, at least) this can be the difference between “yuck!” and “I can work with this!”


Fine Ross/Dyna-Comp-style compression. Added controls permit subtle settings. Great price.

Compressors gonna compress.


Ease of Use:




Keeley Compressor Plus

The first four examples feature the same neutral tone setting, while Clip 5 takes the new tone knob for a spin (first at maximum treble, then in the middle, and finally at maximum treble cut). It’s a nice, workable range suitable for most guitars and pickups. Clip 6 features a vintage Stratocaster on the single-coil setting, while Clip 7 is the same guitar in humbucker mode. The latter isn’t your archetypal clean-toned Nashville squish, but a relatively subtle and potentially useful variation.

Squishin’ Mission
It you already use vintage-style compressor stompboxes, you’ll dig Compressor Plus’ core sound while appreciating its increased flexibility. But before boarding the compressor train for the first time, it may be worth considering options that didn’t exist four decades ago, when the Ross and Dyna-Comp debuted, as well as some downsides of compressor use.

To squeeze or not to squeeze is a personal call. Many players avoid placing compression effects in front of their amps precisely because they restrict dynamic range and decrease variations in amp response. Stompbox compressors are probably most popular in modern country, where they add consistency and smoothness to clean-toned parts. (But can we please dispense with the absurd idea that compression is essential for playing funk?)

Nowadays you can get something close to studio-grade compression in stompbox form. (Keeley’s own Compressor Pro is one good example.) These devices provide more control and less lo-fi coloration—basically, they sound less “compressor-y.” But for some players, simplicity is paramount, and pumping/thumping coloration is a feature, not a bug. The Compressor Plus, to some extent, walks a path between those two worlds.

The Verdict
The Compressor Plus recreates the tones of the most popular vintage stompboxes compressors. Its added features permit relatively subtle settings without getting too fussy. The build is solid, and the $129 price is extraordinary for a quality U.S.-made pedal.

Watch the Review Demo: