Guitar compressor / gate pedal with studio-grade control capabilities
By Phil O'Keefe
There has been two main "camps" in terms of guitar compressor pedals, with each tracing their roots back to either the orange squeezer type of circuit and sound, or the grey box Ross type of sound. Both units offered minimal controls - just a knob or two at most. While some modern compressor variations have elaborated on the one or two knob control layout, few have taken things to the degree that Australia's MI Effects have with their Compressor--one of the most fully featured compressor pedals on the market.
Figure 1: The MI Effects Compressor
Housed in a 4.6" X 3.6" X 2.2" die cast metal box, and featuring true bypass switching, the light lime green powder coating with burnt orange silkscreened lettering on the Compressor immediately caught my eye. Pictures do not do it justice. It's certainly "different" - whether it's bold and daring, or slightly queasy and unsettling is a matter of opinion, but on a pedal with this many controls, I at least appreciated its legibility; it's really easy to see what control you're adjusting. The knob spacing is also set up for ease of use, with plenty of room to get your fingers in between the controls. And that was the second thing I noticed (after the color) - there are a lot of knobs on this compressor pedal; six in total, plus one internal trim pot--which is an unusually high amount of controls for a pedal compressor.
According to MI Effects, they started with a full wave, transistor rectified control signal, which is similar in principle to the old Ross, and then added studio type features that generally aren't found on Ross style compressors--or for that matter, on most compressor pedals of any type. These types of controls are far more commonly found on compressors that are designed for studio use, where flexibility and versatility are in high demand.
For power, the Compressor offers the choice of using the 2.1mm ("barrel style") negative center pin 9V DC jack or 9V battery power. When using an adapter, you can hit it with up to 25V DC without harming the pedal. I didn't have a 25V DC adapter handy, but I did have a go at using an 18V DC power supply, and as I expected, the headroom and "openness" of the pedal improved, and the output increased noticably.
While the large Volume and Sustain knobs feel beefy and firm, there's a bit of wobble to the four smaller knobs. Their location is about as far away from the Compressor's main bypass footswitch as you could possibly get, but they're still somewhat exposed, so if your clumsy friend with the big boots and "bad footswitch aim" wants to borrow your Compressor, you might want to say no; lest he return it with a snapped knob or two. The good news is that MI Effects has opted to use sealed potentiometers, so the controls should stay clean and crackle-free for a long time. The parts and construction appear to be of very high quality, in keeping with MI Effects reputation for first-rate pedal builds; high tolerance (better than 2.5\%) polypropylene and polyester capacitors, metal film resistors and beefy PCB construction are all in evidence, and it doesn't look like any corners were cut to try to save a few bucks.
The MI Effects Compressor should be "dialed in" for each guitar you use with it, which means an extra knob to adjust if you switch between guitars on stage a lot. The idea is to set the sensitivity of the pedal to best match the output level of the pickups. The process is similar to "gain staging" studio processors. You adjust the input Level control until the red Overload LED only flashes on the loudest peaks. The LED actually is calibrated conservatively, and lights up well before the onset of audible distortion, so occasional flashes of red as you play is acceptable. With some single coil equipped guitars, I was unable to get the LED to flash at all, even with the control set all the way up, but when I switched to a guitar with much hotter output humbuckers, I had to turn it down almost half way for best results, so there should be plenty of range available, no matter what kind of pickups you use. Once you have the input dialed in, you can set the output level with the large Volume knob. Setting it for unity gain--so it's equal in volume with the bypassed signal--is the usual approach, but if you like to use your compressor as a solo boost, there's enough level on hand for a pretty sizable volume increase.
ATTACK, RELEASE AND SUSTAIN
Studio engineers and recording enthusiasts will be familiar with attack and release controls. Attack allows you to adjust how much of the note attack--the very beginning transient of the sound--will pass through unaffected before the compressor circuit starts compressing the signal. As you turn the Compressor's attack knob further clockwise, the compressor allows less and less of the note attack to pass through un-modified; the compression "kicks in" faster, and tightens up the note attacks more and more. MI Effects recommends starting with the fastest setting and adjusting it to taste from there, and for general use, the fastest setting provided smooth and even results. However, if you want a little more "cluck to your pluck", you can roll off the Attack a bit and get some great Country approved "chicken picking" tones.
The Release knob controls how fast the compressor "lets go" of the signal. The higher it is set, the longer the compression is maintained, and the slower the compressor's release. A faster release time is generally better for fast playing, and a slower release can help with long, held-out chords, although in real-world use, I was able to leave the Release knob near the middle of its range and still get good general purpose results. By adjusting the attack and release, a wide variety of different compression effects can be achieved - everything from slower attack, fast release poppy chicken pickin' to fast attack and slower release settings for maximum sustain on long notes and chords. The Attack and Release controls tend to interact with the Sustain control in a fairly interactive way, so you will have to play with them a bit to get a feel for how they affect each other. Speaking of the Sustain control, I found it helpful to think of it as kind of a "compression amount" control. It seems to be somewhat similar in function to a combined ratio and "threshold" knob; the amount of compression increases and the onset of compression happens sooner with higher settings on the Sustain knob.
MI Effects recommends using only as much Sustain as you need, and no more. For general level control and dynamics taming, you only need to turn it up about 1/3rd of the way. At around noon on the Sustain knob, Nashville comes a calling. Crank it up, and it sustains for a long time; perfect for flowing, sustain heavy leads and big power ballad power chords. However, as you increase the amount of Sustain, the tone will sound more and more "processed." Rather than viewing this as a negative, I felt it was a great point in the MI Effects Compressor's favor. If you want subtle and transparent compression, this pedal will definitely give it to you, but it will also give you mangled and squashed too, which is exactly as it should be with a compressor that is designed for maximum versatility. The MI Effects Compressor doesn't force its sound on you--it allows you to find your own sound.
Compressors, by their very nature, tame your dynamics; lowering the level of loud peaks while bringing up the relative level of softer signals--including noise. The more compression (by way of the Sustain knob) you add, and the more make-up gain (Volume) you use, the worse the noise level will get. This will be further amplified and accentuated if you place an overdrive, distortion or other high-gain pedal after the compressor. A compressor in front of a Dirt pedal can be loads of fun, but it will amplify any hum or noise in your signal. This is just a byproduct of compression in general, and not a design fault with the MI Effects Compressor. In order to address this issue, MI Effects has included a noise gate. This gate automatically mutes your signal once it falls below a certain minimum volume threshold, which is set by adjusting the Gate knob. I found the gate "chattered" (rapidly opened and closed) a bit as it reached the threshold and closed--especially with high amounts of Sustain, but a little adjustment of the internal gate release time trimpot helped to smooth it out. (Figure 2) It would have been nice to have this seventh control mounted externally, but to be fair, it really is generally a "set it and forget it" type of control, and most people won't need to be making constant adjustments.
Figure 2: An internal trimpot (red arrow) adjusts the Gate release time
As with all gates, the trick with this one is to set the threshold level low enough to allow all of your notes--even the softly played ones--to pass through the gate, but just high enough so that low-level noise signals won't trigger and open it. I must admit to not being a big fan of gating in general, but that comes from my background as a recording engineer. I prefer to capture everything, and then get rid of what I don't need later, rather than rely on a device to make those decisions for me--but in a live situation, a gate can be a real lifesaver, and when properly set, the onboard gate does a good job of keeping background hiss silenced when you're not playing. Having the Gate included is a nice bonus, but you can always turn it off if you don't need it by turning the Gate knob fully clockwise; even MI Effects recommends using the gate judiciously, and only when needed, in the pedal's manual. Speaking of the manual, it is a single sheet of roughly standard sized paper, printed front and back, and it does a very good job of explaining the pedal and its features and functions.
As you may have guessed by now, I'm not particularly crazy about the color of the pedal. That might be due to it clashing with my Sea Foam Green guitar (Figure 3), but who cares? It's not what it looks like that matters--it's all about the sound.
Figure 3: Am I really going to complain about the color of the pedal clashing with my guitar? When there's not much else to complain about, this is what you get
This is a compressor connoisseurs' pedal. If you demand "turn-it-up and go" simplicity, then the MI Effects Compressor is not for you. But if you need a wide variety of different compression effects, or you want to dial in your own individual "sound", and you know how to use (or are willing to learn) the extra controls, then you're going to love this compressor. The degree of tonal flexibility far exceeds that of most ordinary compressor and sustain pedals. While it will do more subtle and restrained compression sounds too, if you're a fan "squishy" tones like I am, you'll have lots of fun. Either way, this is a compressor pedal that lets you decide how you want it to sound. About the only thing it's missing is a "blend" knob (so you can do "parallel compression"), and maybe an alternative color scheme, but you'd still be hard-pressed to find a more versatile or better sounding compressor in pedal format. It may be a bit ugly, but it sounds fantastic!
Dimensions: 3.6"W x 4.6"D x 2.2"H
Bypass: True bypass with heavy duty 3PDT switch and clear lens amber LED for on / off status indication
Warranty: Five year limited warranty