Emulator IIIx : Technical Description

Architecture The Emulator IIIx is a 32 voice, 16 bit, polyphonic digital sampler which uses a National 32CG16 main CPU, clocked at 30MHz. The EIIIx is entirely controlled by computer software (the operating system) which is loaded from 2 Mbytes of CPU RAM when it is powered on. This eliminates the "overlay" delay between modules that is encountered on previous Emulators.

The EIIIx continues with the overall EII/III design, but uses custom E-mu Systems chips for sample access (replacing the complex micro controller circuitry), a main CPU and a scanner CPU (The same as the Emax II - a Rockwell 6502 processor with 192 bytes of RAM!). The 32CG16 main processor runs without a floating point coprocessor (although there is space on the main PCB for one), and boots from two 27C010 EEPROM's with a total of 256 kbytes. A known EPROM version is 3892, and the PCB's went up to at least Rev A.4.

The G Chip To simplify the design and to reduce costs E-mu Systems developed their own custom silicon - the G chip. This is the main digital audio processor, which provides 32 channels of pitch shifting, sound memory addressing and volume scaling,. This frees up the main CPU from this core task

The H Chip Emu also added two H chips which implement 32 digital
4 pole filters as well as the final volume contours. There are two spare slots on the main PCB for further H Chips - they were never filled. They were left free to add further filter technology - we would have to wait until the release of the Emulator 4 to see complex filters.

Sample Memory Up to 32 MB of sample RAM can be fitted to the EIIIx. The sample memory consists of 64 ZIP sockets which can be filled with up to 64 1MB x 4 DRAM 80nS memory chips.
See the Upgrades section for memory expansion information.

Support Chips Two standard 6850 UART chips provide MIDI and RS422 serial interfacing. The EIII SMPTE has been dropped. The floppy disk gets a WD1772 controller, whilst SCSI is handled by a 5380 chip.

Engineering Changes The Emulator IIIx may have had a number of engineering changes - they are currently unknown.

Digital Sampling The EIIIx samples at 16 bit resolution via a Crystal Semiconductor 5326 stereo ADC (64 times oversampling Sigma/Delta), and stores the samples into memory (and disk) as 16 bits. The EIIIx replays at 18 bit resolution via Analog Devices AD1860 DAC's.

The use of the G and H chip custom silicon vastly reduces the complexity of the EIIIx compared with previous Emulators. The circuitry can now fit onto just 2 PCB's. This also increases reliability, reduced heat, and means the EIIIx can be used in live rigs, rather than just the studio.

Digital Filters The EIIIx has 32 digital 4 pole filters, which are a very close approximation to the EIII analog filters, they even have resonance!

Digital Ins and Outs The EIIIx is the first Emulator with digital audio interfacing. The connections are via balanced XLR connectors and they can be set via software for AES/EBU or SPDIF.

SCSI Whilst the Operating System has minor improvements on the EIII, the SCSI implementation is improved. The internal SCSI path length is much shorter, and the SCSI bus arbitration is sorted in the initial release. Two EIIIx's can simultaneously read from the same single SCSI device.

Weaknesses  The EIIIx is innovative from a hardware perspective offering a great sound at a new price point. However the operating system has just a few extra features over the EIII, and it fails to keep E-mu Systems at the leading edge. The use of ZIP memory (which was hard to locate even in 1992) was a backward step from the EIII SIMM's, reflecting Emu's belief that users should not upgrade their samplers (as per the locked up Emax's). Whilst this was to some degree accurate in the days prior to PC users taking their beige boxes apart, it is a loss of the edge that E-mu Systems are famous for.

The EIIIx can suffer from audible noise in the audio outputs generated from the SCSI bus. See the Tech Tips for a resolution.