Keeley Electronics is perhaps the most well-known name in stompbox compression. After all, Robert Keeley’s classic 4-Knob and (recently discontinued) 2-knob Compressors have been going strong for over a decade, surpassing well over 40,000 guitar pedals sold. So when Keeley Electronics finally released their “Guitar Compressor #2”, or GC-2 as it’s called, it raised more than a few eyebrows. But the GC-2 Limiting Amplifier isn’t to be mistaken as a replacement for the legendary 4-Knob Compressor. As the name implies, this pedal’s focus is more so limiting as opposed to general compression. What’s the difference? Glad you asked…
Compression Vs. Limiting
Compression and limiting are essentially variations of the same thing: dynamic control that reduces volume peaks in audio. Basically, these effects make loud sounds quieter. A useful side effect of this is that quiet sounds will appear louder as your peaks are reduced in volume, essentially evening out your overall volume level a bit. This can also result in clean sustain which is very sought after among guitarists. Of course an unwanted side effect of compression/limiting can be that low level noise gets louder as well, making it important to use such effects with restraint and with understanding of how their parameters work.
Essentially, guitar compressors are typically used on the front-end of your effects signal chain. Compression helps even out your playing dynamics for a consistent signal that can be louder, punchier, smoother, and generally more flattering depending on what you’re going for. As limiting guitar pedals like the GC-2 are pretty uncommon, it’s important to understand how limiting is typically used in the studio to figure out how to best make use of such a pedal.
Limiting is one of the most important effects used on mixes and final masters of audio recordings. A limiter is typically the last effect used in an audio path on the master mix bus to put the final touches on the overall dynamics of a recording. Also, the technique of “brickwall” limiting is often used to put an aggressive ceiling on dynamics that prevents any volume peaks from crossing the selected threshold. Being a limiter in pedal form, the idea of using the Keeley GC-2 Limiting Amplifier as an end-of-signal-chain pedal opens up a few possibilities that typical stompbox compressors lack. All of that will be mentioned soon in our review.
The Legendary dbx 160A Compressor/Limiter… at your feet!
The GC-2 packs another surprise under the hood: its “extreme high-fidelity THAT Corp. 4320” chip. These chips were conceived and created by former dbx engineers and deliver performance and response that rival the legendary dbx 160A, widely considered one of the best compressors of all time. The diminutive GC-2 Limiting Amplifier even sports a similar 3-knob control set and hard-kneed compression style as its dbx predecessor. Thanks to this chip and other ultra-high quality components, the GC-2 has a frequency response that extends far outside the typical range of guitar, making this truly a studio-grade pedal. This means two things: your tone will not be compromised and you can potentially use this pedal with other instruments and line signals for a style of compression/limiting that’s reminiscent of that dbx 160 sound. Very cool.
Now let’s run down the features and find out if this is the best limiter pedal around in our Keeley Electronics GC-2 Limiting Amplifier review.
- Studio-grade compression in a pedal
- User-friendly controls so you can find your perfect sound
- Contains THAT Corp. 4320 chip
- Controls for Ratio, Threshold, & Level
- Attack Time: typically 15ms for 10dB, 5ms for 20dB, 3ms for 30dB
- Release Time: typically 8ms for 1dB, 40ms for 5dB, 80ms for 10dB, 160ms for 20dB, 240ms for 30dB
- Powered by batter or 9VDC power adapter (current draw: 15mA)
Sound & Performance:
First, I’m going to evaluate the merits of using the GC-2 Limiting Amplifier as a front-of-signal-chain compression effect. The GC-2 is actually a modified version of Keeley’s Bassist Limiting Amplifier, a pedal designed for extremely smooth and even compression response, essential for consistent bass signals. The GC-2 differs from the Bassist in that it is designed to be less responsive to those ultra-low bass frequencies, instead responding within a range more suitable to guitar. It also has a “snappier” response and a quicker Attack & Release than Keeley’s Bassist Limiting Amplifier. But the idea is that it can really give you a level of compression that’s more even and consistent than what you may have experienced with other compression pedals.
When setting the Threshold and Gain knobs at around noon, you’ll typically achieve a setting that’s pretty much at unity volume with your bypassed signal. And with the Ratio knob rolled all the way down, the GC-2’s compression is at 1:1, producing no noticeable effect on your signal. If the Threshold Indicator LED is flashing red on any hard strumming or plucking, kicking the Threshold up a little towards 1 o’clock or higher ensures it stays green and isn’t compressing at all. From here I noticed something quite amazing. The GC-2 is perhaps the most transparent effect pedal I’ve ever heard. This is a very big deal. Most compressors, even considerably transparent ones including Keeley’s own 4-Knob Compressor, often impart their own sound, however subtle, on your signal. This can be a good thing in some cases and is often a part of what gives certain compressors their sought-after sound. But it’s really refreshing just how “not there” the GC-2 can be when engaged. I A/B’d the GC-2 without compression against my bypassed signal repeatedly and could never accurately tell when it was active or not. It doesn’t get more transparent than this.
When cutting the Threshold down to where the Threshold Indicator LED begins to illuminate red, the GC-2 will begin compressing your signal at a ratio set by the Ratio knob. You’ll notice the compression coming in when rolling the Ratio from 1:1 to 2:1. The GC-2 still maintains its pristine transparency when compressing although you’ll notice it leveling off those volume peaks. Keeping the Threshold around the 10-12 o’clock range with Ratios from 2:1 to 4:1 produces more subtle effects. The compression has a hard knee and combined with the GC-2’s fast attack, produces a tight compressing effect that kicks in instantaneously. On the lightest settings, it’s barely noticeable, maybe taming a volume peak here and there. If you turn down the Threshold a bit and set the Ratio to around 4:1 or 5:1, you can get some pretty heavy compression that clamps down hard while not killing your tone. Very nice.
But the GC-2 Limiting Amplifier’s fast attack, hard knee, incredible transparency, and Infinity:1 ratio give this pedal even more utility at the other end of your signal chain. And that’s where some effects using guitarists will discover how indispensable the GC-2 really is.
If you’ve got a reasonably large pedalboard, you know how problematic it can be to constantly monitor the output levels of all your different pedals. Sometimes an output level gets set too high or maybe you activate 2 high output pedals at once that unintentionally produce a huge surge in volume. By setting the GC-2 to a pre-specified Threshold with an Infinity:1 Ratio, you can set up a “brick wall” limiting effect that will keep any high output pedal from blowing holes in your speakers or shredding your audience’s eardrums. Need a little more headroom for your boosts and overdrives? No problem. Just raise the GC-2’s Threshold to a setting that allows additional volume clearance. Yes, you can save your headroom while sparing your audience from an aural assault because you forgot to roll down the Level control on that monster fuzz pedal of yours. You could simply put it after an assortment of distortion and fuzz effects and get the job done. But there’s one more consideration…
So the GC-2 can prevent accidental walls of noise, but it can also work with such intended soundscapes. Maybe that self-oscillating delay pedal could benefit from a volume ceiling that keeps it from getting too out of hand. Now you can go on with your shoegazing and sonic experimentalism knowing that the beautiful noise you’re creating will have some sort of volume restraint. The GC-2 is perhaps the ultimate end-of-signal-chain pedal, keeping your precious tone in tact while ensuring no unwanted volume levels reach your amp and audience. I’m surprised it took this long for someone to release a pedal that does this job as efficiently as the GC-2 Limiting Amplifier. Big kudos to Robert Keeley and Co. for releasing this essential guitar compressor pedal.
The Keeley Electronics GC-2 Limiting Amplifier solves an unmet need of effects pedal using guitarists, and will find homes at the beginning and ends of many guitarist’s signal chains. (If you’re still unsure of which Keeley compression pedal to get, check out our Keeley 4-Knob Compressor review & Keeley Compressor Pro review.) Let’s see the final result.
The Keeley Electronics GC-2 Limiting Amplifier is a true stompbox limiter and the ultimate end-of-signal-chain pedal for dynamic volume control. Drawing upon the legacy of the dbx 160A, the GC-2 provides a hard-kneed compression that adds punch and clarity to your sound while maintaining absolute transparency. It can be used just as well as your go-to compressor or boost as it’s one of the purest sounding compressors around. But pedal junkies who have large pedalbaords or simply like to experiment and make beautiful noise with a variety of pedals at once will appreciate the “brick wall” limiting offered by the GC-2. Nothing passes until the GC-2 allows it to. It’s definitely the best limiting pedal available today.
That concludes our Keeley Electronics GC-2 Limiting Amplifier review. Thanks for reading.
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