Emulator I - Analog Voltage Interface

Emulator I : Analog Voltage Interface

Overview The Emulator I was released before the advent of MIDI in 1983. The MIDI specification was created by Sequential Circuits and Yamaha, and E-mu Systems were not able to add their influence. They were after a RS422 serial protocol - which is much faster than MIDI. This is why early Emulators and Emax's had the RS422 serial interface - which allowed connection to Mac computers. Dave Rossum (quite rightly) thought this was a better and faster interface than MIDI. However MIDI won the day, and the faster RS422 standard never took hold.

So although the Emulator I eventually gained a JLCooper MIDI external interface, for the first few years owners were after a CV/Gate interface to enable the Emulator to be driven from other keyboards and most importantly from the new microprocessor digital sequencers - such as the Roland MC4 and MC8. Thus was born the Analog Voltage Interface, model number 6040.

Tomita The original Analog Voltage Interface was probably commissioned by Tomita for use in his 1981 Album of Orchestral music, with the Emulator playing Timpani from a MC4B or MC8. The Steve Miller Band used an E1 and this interface on their early 1980's albums. Vince Clarke used one in 1983, probably with his famous MC4B.

Blue Box The Analog Voltage Interface is a large metal blue box with a sloping front. There are 8 sets of CV and Gate jack inputs, located right on the front panel, one for each of the eight voice channels of the Emulator I. Below these inputs are eight toggle switches which control the mode of each channel. The three modes are:

Test - manually switches the channel CV into the E1
Internal - switches the test CV off
External - external gates control the E1

The Blue box links up to the Emulator I via a standard RS232 serial cable. The socket is round the back of the AVI. The voltage per octave can be trimmed via a trimmer which can be accessed through a small hole in the AVI front panel. The AVI must be used with the correct Emulator OS software, or samples can be damaged.

AVI Software The special Emulator OS version for the AVI box has some additional functionality.

Mono Mode - monophonic mode on channel 1
Disable/Enable - turns AVI control on and off
Gate Test LED - GET SEQ LED shows key on/off
Scan Rate Control - speeds up the response time to CV's

Technical The AVI has a Z80 micro-processor running at 5MHz with a 2716 EPROM for the simple operating system. The control voltages are read by an ADC0809 8-bit analog to digital converter. The AVI software behaves as if it were the internal sequencer, so this functionality is disabled in the Emulator. The keyboard is still active, but its best to switch it off using the Scan Rate Control, as the response to CV/gates improves by 10ms to 3 - 4ms.

Success ? Well this box is pretty rare, probably around 50 or so were produced in 1981/83. We know of only three in existence today. When we spoke with Dave Rossum in July 2000, he commented that it was one of the more unusual and less successful items that E-mu Systems made in the 1980's. However low demand for a CV/Gate interface, is understandable, especially once MIDI took off.

Resources

AVI User Manual

Connections

The AVI is connected to the Emulator via a RS232 serial interface and cable. The Emulator acts as the DCE and has a DB25 female socket. The AVI acts as the DTE and has a male socket.

The communication protocol is very basic with only TX, RX and GND signals being used by the AVI, although the Emulator has a more complete RS232 implementation.

The RS232 socket is wired to the Emulator digital board via a ribon cable, and it enters the board via a DIL header called IC41.

Therefore a a standard serial cable wired as follows is required. Only the lower 3 connections need to be made.

E1 DB25

Cable has Male Plug

EI
IC41 pin

AVI DB25
Cable has
Female Socket

DCE Ready

20?

DTE Ready

RTS

CTS

GND