28 April 2013

Pedal Effects: T-Rex Compnova and MXR Dyna Com comparison


Note: this entry was already published in my old Spanish version of this blog, around March 2011. I am just revisiting it here.

From all the pedal effects I've ever tried, compressors were always the most arcane and mysterious. I wasn't never able to understand what a compressor is and, for what or when to use it.
Only when I've started my own home studio and had to deal with tracks and their Peak and RMS levels is when I've started to understand what a compressor does.

Some time ago, I bought a T.Rex Comp Nova, just to have a "complete" pedalboard that "should" include a compressor effect. Doesn't it comes with any multi-effect pedalboard?, it should be important, then!. You know...

Now, with clear ideas, I've decided to give an oportunity to this kind of effect and, I wanted to compare that pedal (bought because of its transparency and dummy-proof controls) against one of the mythic compressors: the MXR Dyna Comp.

And that's all about this entry: how a compressor works, what's its use and, a comparison between a very transparent one (Comp Nova) and a coloring one (Dyna Comp).

What the heck a compressor is useful for?

Let see a very typical situation.
Someday, we see that one of our friends loads a compressor on his pedalboard and, that he/her even uses it so, with lots of curiosity we ask our friend to let us to check that effect.
Usually, he doesn't known how to explain what it does further than "it compresses the sound" or "gives some sustain" or we don't understand a single thing about what he/she is talking about.
Anyway, we switch on the pedal, tweak the knobs and, finally, we don't see how could it be useful for us so, we kindly thank him/her generosity and time and, we go back home thinking: "what the heck wants he/she that pedal for?. I don't get it!".

To not repeat myself, I would like you to read this previous published entry (in Home Studio section), which will let you understand how a compressor works and what it is useful for:

T-Rex Comp Nova and MXR Dyna Comp: similar but different

Pedal Effect compressor are more limited in controls than Studio compressors and, in some cases there is just a knob that controls several aspects of the compression: ratio / attack and sustain. In other cases, there is more control over each individual aspect.
Every compressor does basically same function but, none does it in the same way.

T-Rex Comp Nova

The ¨T.Rex Comp Nova is a very transparent compressor. That means that doesn't color the signal and, the signal remain unaffected when the pedal is switched off (true bypass).
It's a modern compressor and, in principle, not based on the design of any of the 3 mythical compressors but, in a new brand design.

It has 3 control knobs: Volume, Comp and Attack.

With the Attack knob, we increase the delay time between the instant were the sound goes over the threshold and the instant were compressor starts its work. More attack, means more delay and, therefore, more transients or peaks so, more punch and natural compression.

With the Comp knob, we determine the compression ratio or, how much the sound that exceeds the threshold will be compressed, once the delay time selected with Attack passed. The more Comp, the more we will drop down peaks and will tame the percussive sound or punch.

The Volume knob is really the Gain or Make Up control of this compressor and, it's responsible to raise the level of the sound in some dB before the compressor does its job so, it determined the output loudness but, also, which part of the sound is over or below the threshold level (fixed inside the compressor).

On its booster mode (Comp rolled off and Attack at max), it has way low gain increase than the MXR unit. Just 3 dB maximum.

For clean stuff, it's lack of special character (colorless) makes it to sound a bit boring, when you compare it against the sound richness that the MXR generates and, therefore, this is where I like it less.
Combined with the Vibe effect, sounds a tad cool and sharp.

Where it shines best is when paired with gain pedals (fuzz, overdrive and distortion), its transparency and smoothness leave a greater dynamic range to a kind of pedals that, by nature, are already compressing the signal (well, clipping the peaks).
Overall, is a friendly pedal, easy to tweak, with a very transparent sound and, this is its greater virtue and defect. That transparency avoid any sonic fingerprint over your own sound and, as a clean booster works well, rising a bit the overall signal and feeding the rest of pedals with a stronger signal.

MXR '74 Vintage Dyna Comp re-issue

It seems that everybody who knew the vintage unit will say that the sound you can achieve with modern versions of the Dyna Comp isn't the same. One of the main reasons is that the new units have a new chip.

Well, it seems that neither this re-issue of this mythical pedal still doesn't sound the same as the original. In comparisons I was able to hear in Youtube, there is clearly a difference in the sound that the reissue edition produces, compared to the original one. The original one is richer in nuances but, in any case, the reissue version sounds way better than the modern Dyna Comp.

So, not having the money and time to source an original Dyna Comp, I went for the reissue version and, well, it has practically all the goods of the original one and all the bad.

It seems that the chip is the same as in the original. They had to source some NOS chips and therefore, this reissues are limited to the number of available chips. So, I bought it before those chips disappear.

Like in the original, there is no plug for an AC transformer so, you can run this pedal just using batteries. You know, if the battery dies, your complete chain of effects disappear (not true bypass).
I made an small hole on the base, to throw there a battery-clip wire (that comes with the Voodoo Lab Power Pedal Plus 2), because if you don't remove the input jack, you battery will dead in short.

As the original it lacks of a led that indicates to you when the pedal is active, so it's a mess when you are working with subtle compression settings. If you end your session with the effect switched on, next time you use your pedalboard the effect will be active without notice (no led).

This pedal has two knobs, highly interdependent. Any change in any of the knobs impacts in the other knob so, any adjust must involve both knobs to achieve the wanted effect. In this sense, the T.Rex is more friendly to achieve the wanted effect.

The Sensitivity knob seems to work over the whole compression character (ratio), while the Output knob controls the Make Up Gain. It seems that the Attack time is fixed inside the unit.

In booster mode, it adds a warm and musical color and has a gain range at least 3 times the range of the T.Rex.

This pedal sounds fantastic with clean stuff (is THE sound) and, perfectly combines with weak effects, as the Vibe or Phaser. Where I don't like it so much is paired with gain pedals (distortion, fuzz), where the compressed signal has a very limited dynamic range.
But used as a booster combined with gain pedals give a nice warm, musical and colorful resulting sound .

The main issue with this pedal is its high noise level. Its gain is so powerful that the existing floor noise is raised in the same amount. Even that you don't notice it so much during playing, the noise clearly pops up when you stop playing and, more specially, with single coils.

Soft compression levels or a "clean" boosting, make the Stratocaster to sound full bodied and with same authority than a Les Paul, maintaining those sweet strato trebles but, with greater richness.


The compressor should be the first pedal in the chain, at least that it enters in conflict with Wah and / or Fuzz. This is the best position because is the spot were the floor noise is the less and, because it modifies the natural dynamics of your guitar, before applying any other effect.
Well, when I bought that MXR reissue, I wasn't very confident of its sound but, it impressed me so good that I've substituted the T.Rex with this MXR.
Anyway, the original issues are still there and, only the time will say if it will remain in my pedalboard.

If you work mainly with clean stuff, the MXR will do a better job but, if you work mainly with gain pedals then, you will love the smoothness and transparency of the T.Rex.
Update Note:  After several compressors, my definitive compressor is the Wampler EGO. My search ended there so, be sure to check that one.


As music is very subjective, I prefer that everyone can see how each compressor works and decide by itself which one better suits its particular needs.

Part 1

In this part, I am describing first the function of a compressor effect and, I start comparing both pedals working with very similar compression levels, to clearly hear how each one colors the signal.
Both pedals are tested with a clean signal and then, with gain pedals (RAT 2 and OCD).

Part  2

In this part, I am comparing both pedals paired with a Vibe and a Fuzz, were we can see very clear differences respect of their work.

Part 3

This third part is exclusively dedicated to explore the possibilities of the MXR Dyna Comp alone.

Part 4

The forth part is dedicated to explore the possibilities of the T.Rex comp Nova.

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