Emulator III : Technical
Description
Architecture The Emulator
III is a 16-voice, 16-bit, polyphonic digital sampling
keyboard, which uses a National 32016 main CPU, clocked at 10MHz.
The EIII is entirely controlled by computer software which is loaded
from disk when it is powered on. The EIII kept with the overall EII
design, using a micro controller for sample access, a main CPU and a
scanner CPU (Rockwell 6502 processor with 192 bytes of RAM! - as
used in the Emax II). The 32016 main processor and
32081 floating point coprocessor run the operating system from 128k
bytes of DRAM in overlay mode (each module is loaded from disk when
needed). The 32016 boots from two 27128 EEPROM's, this is the
firmware that can be seen loading on the LCD when the EIII is first
powered up.
The F Chip To cut down on costs and to reduce the amount of complex
circuitry, E-mu Systems developed their own F-chip to act as a
custom timer for each channel and a 2x oversampler for the
DAC.
Digital Sampling The EIII samples at 16-bit
resolution, and stores samples into memory (and disk) as 16 bits.
The EIII makes extensive use of TTL integrated circuits and CMOS
memory with some custom chips produced by Emu, and some Programmable
Logic Arrays (PAL's). The large number of chips are held in a
horizontal card frame of 5 large PCB's. The frame is isolated from
shocks by flexible mounts on the main casing.
The EIII's can
be tempremental (often requiring an annual service), and some of the
connections to the PCB's can cause problems. This is really a studio
instrument which you should avoid gigging, not least due to the
expense of anything going wrong. Parts are not cheap and servicing
can be time consuming. Take care of this baby !
Support
Chips There is a
floppy disk interface handled by a WD1772 chip, with SCSI handled by
a 5380 chip, and a 82530 for serial communications to MIDI and
RS422.
Sample Memory The 4 or 8 MB of sample memory on the EIII consists of 16 x
256kbyte (150nS DRAM), 4 or 8 x 1 MB (120nS DRAM) fitted on
the top circuit board. Memory prices had reduced since the EII was
manufactured (1024kbyte max.) but the costs are still unbelievable
today, with 4 MB costing $1800 in 1988. See the Upgrades section for
memory expansion information.
Engineering
Changes The Emulator
III has had a number of minor circuit board changes to address early
problems with MIDI, SCSI and a revised mounting for the internal
Hard Drive (to increase its isolation from the case - thereby
improving its chance of survival in a shock).
Digital
Converters The stereo
ADC is a Sony 20018 (rather surprising !) and the 16 voice DAC's are
PCM53JGI's. Not your run of the mill Analog Devices in this one !
Analog Filters The
EIII has 16 analog filters (a Curtis CEM3387) which combine a 3 pole
low pass filter, a 4 pole low pass filter with Q, plus gain and pan
VCA's. That adds up to a 7 pole analog filter ! They sound very
pleasant. The main 32016 CPU generates software envelopes for the
filters and VCA's - they are therefore consistent and they can be
fast. |