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ESI-32 : Technical Description
ESI-32 Variations The original models are called the ESI-32 from a technical perspective, and the main PCB board is part number PC418. There is no onboard SCSI and the master clock
circuits were implemented with standard logic.
Later models are called technically called the ESI-33, although this was never known publicly. The ES-33 has several cost saving design changes, such as onboard SCSI and the LCD became a backlit LED, and the DSP header was removed. The ESI-33 has a main board part number of PC517.
Architecture The ESI-32 is a 32 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 ESI-32 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 ESI-32 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 ESI-32. 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 32 MB of sample RAM can be fitted to the ESI-32 within two 30-pin SIMM sockets mounted at the front of the motherboard.
Support Chips
MIDI is now managed directly by the main processor, alleviating 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-32 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 low pass filter in front of the ADC. The ADC doubles up, when not sampling it reads the volume pot voltage!
Sample Replay
The ESI-32 replays 32 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-32 has a motherboard for all the primary electronics. There is a daughterboard for both the SCSI expansion and TURBO card. The front panell has its own PCB.
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