The Votrax ML-1 Multilingual Voice System

A Votrax *DISCRETE* Speech Synthesizer!
BIG thanks to Lord Nightmare for loaning this to me!

Wowza! Here it is. The infamous Votrax ML-1. This is one of Votrax's discrete speech synthesizers. There is no custom speech chip, no microprocessor, no microcontroller. It is all 100% discrete analog and digital logic chips, along with a fleet of resistors and capacitors.

This set of pages will document my progress on reverse engineering this device from the digital logic to the analog sections, as well as hopefully a modern 100% reimplementation of everything using modern-day parts and design techniques.

The following pages are in forward chornological order, basically. I will be working on each board individually, and each board will get its own page. Complete schematics of each board will be provided as well as EPROM code (what little there is).

Inside the unit are 8 circuit boards, and 3 backplane boards, along with some power supply electronics. The power supply will not be reverse engineered or further examined since it's really old and would not be of any value. Today, the power supply would be made using some form of switching regulators or similar.

Unfortunately, no less than 4 of the PCBs are fully potted. These 4 boards comprise the main guts of the unit, of course. From what I've read and can tell, the four boards are: Vocal Tract, Timing Generator, Transition Generator, and Fricative Generator. These names sound as good as any right now. I won't know what the boards really do until they are stripped of their potting compound.

Alright, on with the show!

01/09/06: Overview of the device and my disassembly of it.
01/19/06: Audio Samples of the Votrax ML-1.
01/09/06: PCB's in the card cage.
01/18/06: RS-232 Board Part Number 1531
01/18/06: FIFO Board Part Number 1501
02/28/06: Analog/Logic Board and voiced osc. filtering Part Number 1506
02/28/06: Brown Board Phoneme long transition filters, power supply. Part# 1507 (potted)
02/28/06: Green Board Fricative source, phoneme timer, more transition filters. Part# 1508 (potted)
02/28/06: Grey Board Transition/filter/voiced osc. Part# 1509 (potted)
02/28/06: Red Board Vocal Tract. Part# 1510 (potted)
02/28/06: Backplane All 8 PCB's plug into this board.

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