Original Design: Linear "Dynamic-Locked-Loop" (c)2007 JC Maillet

To my knowledge this is the first comp/limiter design that employs a linear gain control block in conjunction with a linear controller inside an NFB servo loop ... analogous to how Phase-Locked Loops operate (with acquisition and lock ranges) the Linear Dynamic-Locked Loop circuit avoids the offset/drift inducing mechanisms seen in opto and FET voltage divider based circuits and non-linear controller based loops which tend to over-squash when driving the input too hard (Orange Squeezer, MXR Dynacomp, etc ...) ... this circuit also avoids using a averaging cap charger circuit ... these aspects help guarantee a response that is devoid of secondary "humping" artifacts ...

the signal path makes use of a circuit idea that produces a zero-phase distortion signal path response as well as a variable gain amplifier that maintains it's dynamic headroom to over 40db of gain reduction - not that it's necessary - and also maintains a high Signal-to-Noise ratio over the whole gain range ... to my knowledge there is no gain reduction circuit that exhibits such a wide dynamic linearity range, constant noise behavior and zero phase distortion all at once ... the combination of characteristics combine to produce what could be a theoretical upper limit for active-circuit based transparency in compressor/limiter designs ...

The controls are quite intuitive and in fact both necessary and sufficient in setting the repsonse characteristics of the loop ... from left to right: Input (Pre) Signal Gain, Sidechain sensitivity - a redundant control that can help compensate for weaker sources, Ratio, and Threshold ... the switch at the top selects between Limiter and True-Compressor modes ...

NOTE: there is a LOT of confusion about how to define Limiting versus Compression action. Limiting is simple, it does nothing until the signal reaches a certain envelope power level (threshold) and then the gain block starts attenuating the transfer gain as a means of preventing the output from getting too large - by how much it reduces the gain in response to signal levels translates into a form of Ratioing. Varying the Threshold and Ratio levels simply gives different limiting characteristics. True Compression on the other hand aims ALSO to make soft passages sound equaly loud inversely similar as when loud passages made less loud by the dynamic equalization process - most so-called compressors sold on the market are really limiters. While a limiter will exhibit fixed gain when signal lies below a threshold level, the compressor will reverse it's dynamic action and increase the gain of its amplifier in response to a decaying signal when approaching the cutoff Threshold level from above. Because the open-loop (compressor) gain has different characteristics than the closed-loop (limiter) gain the Threshold control plays a slightly different role and needs to be adjusted accordingly. True compressor circuits are not typically found on the market because they can get weird if you let them run off on you and let the gain drift to super high levels - it's a balancing act that can be tamed by inserting some string noise every so often. The C/L switch on this L-DLL circuit switches between Limiter and true-Compressor (floating gain) modes ... it is now my favorite Limiter to stick between a single-coil PU and a Single-Ended amp, you can't tell it's there when set right ...