Keeley Compressor Pro Review

    Sometimes you just want tone to come through uncolored. That's where the Keeley shines.


    Like the Keeley Bassist and GC-2 Limiting Compressors the Compressor Pro is transparent and very natural sounding. It is based on the same high-fidelity THAT Corp. 4320 as the GC-2 and it uses high performance Voltage Controlled Amplifiers we well as ah on board true-RMS detector.


    You get a wide range of control to dial in your tone, or flip the Auto switch to On to bypass the onboard Attack and Release controls and let the compressor dynamically manage their timing in direct response to your playing. More on that later.



    There are 5 dials and two switches as well as an array of Compression LEDs. The Footswitch is true bypass. In and Out jacks are top mounted as is the 9-volt DC input. A power LED lights blue when the pedal is engaged and a green LED flashes red when signal is over threshold. Between the Compression LED's and Threshold LED it is easy to understand exactly what the compressor is doing.

    The Threshold knob has a range of -50db to +10db with interval markings all the way around the dial. Use this dial to control the point at which the compressor kicks in based on the incoming signal of your instrument. The Threshold LED helps you know when you are compressing your signal because the green LED will change to red as the signal crosses the threshold. There is plenty of range and will easily accommodate a wide variety of instruments.

    The Ratio knob has a range of 1:1 all the way to infinity:1 which means the Compressor Pro covers anything from light compression to limiting. At infiniti:1 the output level will never increase in output level no matter how loud the input. Every setting across the dial is useable.

    The Attack knob controls the time it takes for the Compressor Pro to start compressing and has a range of 15ms to 150ms. All the way counter clockwise will be a faster attack meaning the compressor will clamp down sooner. If you prefer a slower attack allowing more transient through you will want the dial to the right of noon. Again, every setting across the dial is useable.

    The Release knob controls the time before the Compressor Pro releases or stops compression and has a range of 15ms to 3 seconds. Rotate the dial more clockwise for slower release and more sustain. I found I really liked the release around noon.

    The gain control sets the output level of the compressor. There is plenty of gain on tap and settings above 1:00 or so will start introducing noticeable noise. This dial does not affect the compressor itself in any way. It only controls the makeup gain. +20 db of boost is possible though I can't imagine needing that much in most any case. I kept the gain at just slightly above noon for just a little bump above unity.



    If that weren't enough, you still have the Knee switch allowing you to tell the compressor to react in a hard or soft fashion. “Knee” refers to how quickly the compressor clamps down on the signal once it surpasses the threshold. Basically, if you desire to squash your signal’s transients quickly flip the switch to hard knee compression. If you want the compressor to more gently tighten up transients flip the switch to soft knee. Nice!

    Have you ever been in a situation where you just don't have sufficient time to dial in your compressor? Don't worry. That's where the Auto setting comes to save the day.

    Flip the switch to on and the Compressor Pro will dynamically manage the setting of Attack and Release times based on your playing style. This will sound natural and work in most cases. According to the manual the Compressor Pro looks at the input signals (like guitar, bass, vocals or drums) and determines the correct attack and release times depending on what you’re playing and what signal levels are being detected. In real world usage, it works too. When in auto mode, you essentially have the Keeley GC-2. Threshold, Ratio, and Gain all function in auto mode just like the GC-2.



    I really thought I would prefer using my ear to dial in my preferred settings and have little use for the Auto setting. Frankly, the auto setting just flat out works though.


    I would easily be happy with the Compressor Pro in Auto mode. So then what's the point of buying the Compressor Pro over the GC-2 (or Keeley Bassist)?

    Notably the Compression LED's for one and the Soft and Hard knee capability. But having full manual control is very nice, especially for recording scenarios or even to train your ear to compression. With the markings around the dials it is easy to understand just how you are dialing in the compressor and so even players new to compression should not fear this device.



    Transparency and natural compression is where the Keeley Compressor Pro shines. In my earlier review of the Keeley Bassist I said,


    "It [Keeley Bassist] is so easy to dial in and that makes it great for live situations or when switching between instruments. It is very transparent. What you feed it is what comes out. Just more squished. On that subject it can get pretty squashy if you set the threshold too low."

    As expected, that is true of the Compressor Pro too.


    I also said,


    "It [Keeley Bassist] is intuitive (at least for me) and not a lot of knob fiddling is needed. I also really like that they marked the knob rotation to know where you are at in terms of ratio, etc. Plus it sounds really good. Just seems very transparent but adds just enough "bump" in gain or tone or whatever."

    That is also true of the Compressor Pro. Is the additional price tag worth it over the GC-2 or Bassist? I'll leave that to you but I do really like the 7 LED Compression meter and the Hard/Soft knee switch a lot. Given the option, I prefer having manual control over my compressors and the Keeley Compressor Pro offers a lot of control but remains very easy to dial in. It's hard to make a bad sound. It's the best of both worlds — Simplicity and control.

    The compressor itself seems to be built very well with an attractive charcoal sparkle paint enclosure. There is nothing that feels or looks cheap.


    It does not have a dry/wet parallel blend but I never felt like I needed that. There really isn't any noticeable loss of lows or highs and all of my basses still sounded like themselves, just more compressed, even, and a little fuller. Don't expect "tone magic" or big punchy sound.


    It's not the Diamond, JHS Pulp 'N Peel, Cali76 CB, or Doc Lloyd Photon in that regard. But if you are looking for a natural sounding compressor and like the sound of your basses or rig already, the Keeley Compressor Pro is a compressor to be on your radar. Your tone isn't going to be significantly altered.


    There's a lot of love already for the Keeley Bassist amongst bassists and GC-2 among guitarists. The Compressor Pro just takes things further with some real nice additional variability and control. Is it a problem that the Compressor Pro is built off the GC-2 and not the Bassist? The difference is one capacitor that makes the GC-2 react less to low end peaks. The Compressor Pro sounds great down low.


    There is enough variability to use the Compressor Pro as just a little bit of light evening out in one gig all the way to limiting the spikes in another gig. It is definitely a versatile box. There's a reason why Robert Keeley is so respected in this industry. The Compressor Pro is a testimony to quality and audiophile happiness. It simply works well and I suspect it would sound great with any bass from low output to high output, passive and active, fretless and fretted.



    Retail price: $299


    Robertkeeley.com

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    Reviews by Chris Tromp 

    Bassist and Marketing Guru

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