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ESI-4000 : Technical Description
Architecture
The ESI4000 is a 64 voice, 16-bit polyphonic digital sampler, based very closely on the electronic design of the Emulator IIIx, but with a cost reduced hardware platform.
The main processor is a 32-bit Motorola 68306 clocked
at 16 MHz The ESI4000 is entirely controlled by computer software (the operating system) which is loaded from 2 EPROM's at power on, into a single 512k bytes of OS memory. This is the first time that E-mu Systems used an OS held only
in silicon, with no ability for updates from floppy diskette. Each new OS requires a new pair of EPROM's to be fitted.
Non Volatile Memory The ESI4000 stores a variety of settings, such as LCD angle and MIDI settings,
in a small 128 byte 93C64 EEPROM. This ensures the setting are maintained during power downs.
The DSP Chips
E-mu Systems continued their exploitation of custom designed DSP chips for the core sampling technology in the ESI4000. This time round the sampler makes use of a Version 2 G-chip for 32 channels of pitch shifting, sound memory addressing and volume scaling,. This frees up the main CPU from this core task. The other DSP is a Version 1.5 H-chip for the digital filtering and volume shaping. This chip is move powerful than that used in the Emax II and Emulator IIIx, enabling a wider range of filter type to be implemented.
Sample Memory Up to 128 MB of sample RAM can be fitted to the ESI-4000 in two 72-pin SIMM sockets mounted at the front of the motherboard.
Support Chips
MIDI is now managed directly by the main processor, aleavating the need for UART chips. The floppy disk is interfaced using an Intel 82078 controller, whilst SCSI is handled by a NCR 53C80 chip.
Digital Sampling The
ESI-4000 samples at 16-bit resolution, and at 44.1kHz, via a Philips SAA7360 analog-to-digital converter (ADC) using 3rd order Sigma-Delta modulation, 128 times oversampling and a four stage digital decimation filter. There is a simple
single pole anti-aliasing lowpass filter in front of the ADC. The ADC doubles up, when not sampling it reads the volume pot voltage!
Sample Replay
The ESI-4000 replays 64 voices via a stereo main output and a sub-mix stereo output. All outputs are at 18-bit resolution. Four Analog Devices AD1860 DAC's are used, with a 3-pole reconstruction filter over the output to smooth the "stairsteps" of the signal. The cut off of this filter is 19.5kHz. The DAC's are the same converters as employed in the EIIIx and Emax II.
OS The Operating System is a minor refinement of the OS used in the Emulator III and IIIx. The re-use of the EIII code base reduced the development costs of the ESI range.
PCB's
The ESI-4000 has a motherboard for all the primary electronics. There is a daughterboard for the TURBO card. The front panel has its own PCB.
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