Valley People Dyna-Mite: This is a vintage line-level rack unit, which was available in a few different versions. There were three editions over time, and they were configured either as stereo/dual-mono, or as one mono channel combined with one of Valley's preamps. I have now owned two of them, but they were both the earliest edition with silver aluminum trim framing the face. At some later time I'll try to review the later editions, but for what it's worth I have read that they are not so different-sounding. The Dyna-mite can perform limiting, expansion, gating, and de-essing, although each channel can only perform one of those functions at a time.
The limiter is powerful and not subtle. At a high threshold setting, it does an excellent job of squashing down any big peaks, without disturbing your tone when the threshold is not crossed; though during the squashing, the high end can get a bit muffled or "darkened". Aside from that there is no loss of highs or lows. At lower threshold settings it squashes the daylights out of your signal, with obvious "pumping and breathing", and much darkening of the tone. However this is a very cool effect, and it can add a funky motion to your action, as well as allowing you to really pummel the listener. The attack is fast, but you may hear a "tic" at the beginning of each note, as it takes a few microseconds for the limiter to clamp down on the initial spike. Adding more make-up gain does raise the noise floor, but it's not too bad; and at higher thresholds, there's not much noise at all.
The gate and expander are among the best I've ever used. The attack is natural enough, the release is adjustable and smooth, and the dynamic range of the process is widely adjustable--a feature that is absolutely mandatory for the best gating or expansion results. The range controls allows you to set it up to subtly adjust the noise floor between notes, rather than hard-chopping on and off like most other gates. Or it can chop hard if you want it to. De-essing is achieved with a setting of the expander that only reacts to high frequencies, which is again subtle but very useful. The processor can also be triggered from an external source, for side-chain effects.
The controls include threshold, release, three mode/detector switches, range, and output. Each of these controls works differently than what you'll find on most other comp/limiters, so I'll have to explain them. The threshold control has an automatic make-up gain connected, so lowering the threshold automatically adds more gain, and raising it lowers the make-up gain. The output control is not a standard "volume knob"; instead it sets the maximum level of the make-up gain. In this way, once you have found the output level that best matches the rest of your system, you can adjust the threshold all you want without having to adjust the output again. For line-level use, an output setting between 0 and 5 is appropriate; if you get any clipping, turn that knob down just a bit. The release time control is normal. The first detector switch selects between internal (normal reaction to your signal); "ds/fm", which is the frequency-specific setting for de-essing; and external, for side-chaining. The mode switch selects between expansion/gating, "out" (bypass), and limiting. The out/bypass is super clean, however your level when bypassed will be at the maximum level set by the output knob, so it can be difficult to get unity gain if you plan to switch the limiter on and off during a set of tunes. The next detector switch selects between gate, peak detection, and "avg" RMS average detection. Each will get you different gating or expansion action, all potentially useful, although I find the avg setting works most smoothly. The range knob controls the dynamic range of the expansion or gating, which again makes a world of difference in the audible quality of the effect. Neither the range knob nor the second detector switch do anything at all when the mode is set to limit. It is definitely worth your time to get a copy of the manual! It's very educational.
While the Dyna-mite is intended for line-level signals, and has only balanced inputs, the combined threshold/gain control has enough range that you can send it an unbalanced instrument-level signal and still get decent results. There may be a bit more noise, and the input impedance is not ideal for passive instruments, but it works well enough.
As a compressor, the Dyna-Mite is not very versatile or transparent sounding; but for what it does well, nothing else even comes close. This is my favorite unit for gating, for squashed-with-a-sledgehammer limiting, and abusively loud sound.