Minor Experiments in Electronics
by Dave


Today's Experiment

Votrax SC-01A Speech Synthesizer IC

My very own Votrax SC-01A

Developed during 1979 and marketed beginning in 1980, the Votrax SC-01A speech synthesizer chip was the first phoneme-based language chip available for consumer-grade applications. Many hobbyists, including myself, ended up with one just to mess around with. Votrax seems to have since gone out of business, but I still have my SC-01A. Here, we'll see if I can fire this old thing up one more time.

Here's the Votrax SC-01A data sheet. It was grabbed from another SC-01 webpage. Here's the Votrax SC-01A Speech Dictionary and Programming Guide. I scanned and OCR'd the programming guide myself. It's copyrighted by Votrax, but since they're out of business I can't imagine they'd object. Please let me know if you discover otherwise.

The Votrax SC-01A saw service in the Q*Bert arcade video console. Random bytes were piped to the speech chip to give the impression of another language. It sounds like complete gibberish. Here are a few examples of the SC-01 in action, Q*Bert-style:

qbert-00.wav | qbert-byebye.wav | qbert-fall-cussing.wav | qbert-ugg.wav | qbert-wrongway.wav

Okay! On with the project! Here's the plan: since it's already set up and waiting in the experimenter's breadboard, I'll use a Microchip 16F877A to handle the SC-01A's I/O and memory requirements. A 74LS164 8-bit serial-in parallel-out shift register will accept data from the PIC and parallelize it for the SC-01. The PIC will supply all 6 phoneme bits and both inflection bits. I'll pipe the 'analog' sound output from the SC-01 to the amped speakers that came with the computer monitor so I don't have to breadboard a LM386-based audio amp.

Here's the completed breadboarded project:

SC-01A Project

Well, instead of recoding anything new, I simply whipped out an old code sheet left over from when I first came into possession of this SC-01A. I was in the 10th grade at the time (1983), and the natural tendency of teenage boys is to, well, you know... act retarded. So, no matter the technical ability of an individual teenage guy, its practical use seems to be applied to the lowest form of humor! I was no exception. It seems that my dislike for a particular biology teacher comes through on my coding example from 21 years ago! So, without any further delay, here's some programming sequences and samples of the output:

Example One:

  • Programming Sequence:
    3E, 0C, 0B, 1F, 0A, 12, 3E, 2A, 33, 19, 3A, 3E, 0B, 09, 12, 3E, 06, 21, 29, 3E, 1D, 2E, 2A, 3E, 0E, 27, 2A, 10, 3E

  • Translation:
    "Mrs. Tucker is a fat bitch."

  • Sounds like:

Example Two:

  • Programming Sequence:
    3E, 11, 32, 31, 2A, 3E, 29, 34, 34, 2B, 3E, 1D, 06, 21, 29, 1F, 3E

  • Translation:
    "Shut your face."

  • Sounds like: