Although many plug-ins and hardware effects boxes purport to deliver the “classic sound” and “analog warmth” of old favorites, few of them can begin to match the delight I felt when I first heard a bass guitar track brought to life by a Pultec EQP 1A-3. The Sintefex FX2000 analog sample digital stereo equalizer/compressor uses “dynamic convolution” to provide retro warmth with modern digital precision and maximum control. While lacking the big knobs (chicken heads on the Pultec) and heavy chassis, it’s the closest thing to a Pultec 1A-3, Fairchild 660 or Urei 1176 that I’ve used in recording and mixing.

The FX2000 is a stereo “spin-off” of the more full-featured FX8000. The FX8000 uses dynamic convolution to sample an analog process and digitally reproduce it with a highly accurate simulation of the original’s frequency response and distortion characteristics. While the concept of convolution is not simple (mathematically or empirically), one may think of the process as using audio samples to scale filter impulse responses. For those who have worked with Sonic Foundry’s Acoustic Mirror, the characteristics of an impulse response in audio will be quite familiar. (For a simple

graphical approach to convolution check out the java applet at http://plaza.harmonix.ne.jp/~tosiwata/cnv.html.)

Michael J. Kemp, co-founder of Sintefex with Mike Eden, designed the FX8000 (as well as its stereo “children” the

FX2000 and CX2000). Kemp gives an operational definition and overview of the dynamic convolution process in his

AES Pre-print, “Analysis and Simulation of Analog Dynamic Compressors and Limiters in the Digital Domain.” He

describes it as using non-linear synthesis to analyze and simulate classic hardware compressors and equalizers. This

involves using level-dependent impulse responses, measurements of attenuation characteristics against various signal

amplitudes and applying these in simulation via bilateral dynamic convolution on a sample by sample basis. It’s

immediately apparent that these Sintefex boxes require a lot of horsepower under the hood.