A legendary E-mu samplerThe E-mu SP-1200* has a sound of its own, with a low sampling resolution and theoretically imperfect ADC, DAC and detune parts. The device was designed with a relatively low price point in mind and engineering compromises had to be made that led to evident shortcomings. It appears though that these shortcomings soon became strengths in the hands of artists, leveraging that very distinctive sound to make it the signature of a whole musical genre.
Analyzing, Modeling, Implementing...We have developed an emulation process of the SP, the SP engine.
Parts of this process are based on models from the 2007 paper Physical and behavioral circuit modeling of the SP-12* sampler by David T. Yeh, John Nolting and Julius O. Smith from the Stanford Center for Computer Research in Music and Acoustics (CCRMA).
Evidently, there is more to the SP sound than some simple bitcrushing, and the whole process implies, among other things, four resampling steps and two precise filtering convolution steps.
The influence of a workflowThe limited sampling time of the E-mu device also played a big part in the final sound, as it was common practice to pitch-up the source before sampling (eg 45RPM for a LP record) and use the detune slider to lower its pitch back to normal. This was initially done to virtually extend the sampling time, but this also exacerbated the multiple aliasing artifacts responsible for that gritty sound that we have learn to recognize and love.
Emulating the sound without considering this kind of use would be a big loss, as this is the catalyst of the SP sound. The SP engine includes the source pitch at its core, and makes use of it in the SP950 effect plugin in the form of a combined RPM/detune slider, and in the SP950 web app with a "speed" option.
Another interesting combo was the association of an Akai* S900 or S950 sampler with its steep low-pass filter. The digitally-controlled analog 6th order Butt filter is also emulated inside the SP engine, and put to good use in the two aforementioned SP950 pieces of software.