Extensive compressor reviews and FAQ

Gurus Optivalve: This is an optical compressor with a tube gain stage, similar to the Maxon RCP, Guyatone TCX, EHX Black Finger, Retrospec Squeezebox, and many others.
The 12AU7 tube in this pedal is powered by a low voltage, low current DC supply. As is usually the case, this results in a dull, mushy, unfocused sound. Yes it is "warm", which is what people usually want from tubes, but it sacrifices punch, articulation, balls, and other qualities people want in their tone. I've written about a couple of other tube pedals where low voltage powering works just fine, or where their sound might be mushy but it's still very cool; this is not one of those.
It's also a bit noisy at all settings. The noise isn't the worst I've heard, and in fact it might not be noticeable in an amplified band mix, but you wouldn't want to use this pedal for recording. On the plus side, there is no loss of highs or lows at all, and the frequency response is fairly flat.
The knobs include Input gain, Output volume, Ratio, and Tone. Input controls the threshold. With most of my instruments I found I had to crank the Input up near maximum in order to get a noticeable compression response. There is an LED indicator for the amount of compression, labeled "magic eye"; it works, but it only lights up noticeably when you hit it with a very strong spike, or turn the Input up high. The Ratio control goes all the way from 1:1 to infinity:1, for everything from the gentlest compression to the hardest squeezing. The action is fairly smooth, and does not do any rubbery effects or swell of sustain. The attack and release times are pre-determined by the opto component, and are fairly quick. The Tone knob is a simple EQ that just turns down the highs and high mids in a broad curve above 1 KHz. Its maximum setting is flat, no EQ.
In addition to the magic eye, the rest of the faceplate also lights up with cool backlighting. It looks quite neato. The housing is larger than the "medium" size of the standard Barber or Diamond, and the construction quality is pretty good. It runs on standard Boss-type 9V DC, or up to 12V. The footswitch is "true bypass".
Price in USD: $385 to $395 new, and about half that used.
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