Vox Cooltron "Snake Charmer": This is one of the most "effect-like" comp pedals I've ever tried. At its most minimum settings, it is as squashy as an Orange Squeezer. At its maximum settings, it is like the Boss Slow Gear, a backwards envelope effect. In between, it makes your instrument sound like it is being played with a rubber mallet, underwater. Percussive yet dark and gloopy like molasses.
There is no loss of lows at all, and in fact the low end can get pretty massive. The highs are rolled off drastically the more each note is compressed; since most of each note will be above the threshold, that means the highs are reduced most of the time, to varying degrees. But the tone will brighten at the beginning and end of notes, whenever they are below the threshold. In this way it acts a bit like an envelope filter. The lows and mids are very strong though, so the overall EQ shape is exaggerated and unnatural (though cool as an effect). Aside from the EQ shaping, the tone is thick and tubey. There is not much noise from the unit itself, but at the high ratio setting any background noise or hum already present in your signal gets amplified quite a bit. At low ratio it's not bad at all.
The controls include volume (output level), attack, release, "emphasis", compression, and a high/low ratio switch. The emphasis knob controls the amount of the high frequencies fed into the compression circuit. However what that really means is that at maximum emphasis the highs are merely blanketed during envelope peaks, while at zero emphasis they are absolutely buried. Again though the tone does open back up as the envelope releases. The compression knob controls the threshold, going clockwise from high threshold to low. The manual claims this knob also controls the ratio, but they base that on a misunderstanding of how the word "ratio" should be used. The actual ratio control is just a high-low switch. The difference between high and low here is huge! At low ratio the compression is almost normal, but at high ratio we are fully in effect-land, with deep swoops below unity. Make-up gain here is automatic, so that the lower you set the threshold, the higher the makeup gain. I was dubious about this system at first, but it actually works quite well. It effectively allows you to make any changes in compression amount without having to adjust the output level to compensate.
Compared to some other tube pedals:
The Markbass is much cleaner and more transparent, and capable of much greater subtlety, with less extreme envelope-changing on the "funkier" end of the threshold range.
The Maxon RCP and the Guyatone Flip both have similar tube tone coloration, but with far better high end--though they are also far noisier. Neither of them has the extreme envelope range of the Vox.
The EHX Black Finger can be pretty similar in both tone and effect, though less dark-sounding and more noisy.
The Retrospec is in a much higher class of tone quality, but the Vox can achieve a "rubbery percussion" effect similar to the Retrospec.
This pedal runs on standard Boss-type 9VDC. Vox claims to have developed a system that allows its 12AU7 tube to operate optimally at that low voltage, running cool rather than sending high current to the heater component, hence the name "Cooltron". I can't say whether they succeeded, necessarily, since this pedal sounds so different from the other tube compressors I have used recently or currently. But it does have thick warm tone, without any obvious clipping.
The pedal is huge, it's even bigger than the Markbass. The construction quality is mixed--some parts seem rugged, other parts don't. For example four of the body panels are steel but the other two are plastic. There are blue LEDs lighting up the tube; on the one hand I hate when companies light up the tubes to make them seem more excitingly active, but on the other hand at least it's not "fake tube glow" from an orange LED, as some others have done. The footswitch is "true bypass".
If you want compression "as an effect", the Vox will do that for you better than most others.
Price in USD: $50-$100 used, no longer available new.
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