The speech 64 was invented in 1984 and was one of the best speech device invented for different computers version. Different speech devices where invented but the Currah version was considered far ahead of the others. The only drawback of the speech cartridge was that you need to have the hardware in order to reproduce the speech back. The one we are reviewing is the Commodore 64 version as this was the most featured version with its prebuild commands and ease of use.
The core for all Currah versions is the IC Chip from Texas Instruments SP-0256-AL2.
This chip can reproduce a robotic voice by varying an already determined music note that is impressed on the chip and with the aid of a digital filter it creates a digital output of a voice, which is reconverted to an analogue output through a low pass filter. This sounds a bit complicated but in reality this technique was already in use in the 30’s to reproduce a speech, and with just 10 key notes it could produce speech. This type of machine was called The Voder. After 30 years the Voder inspired inventors to start producing digital speech devices using computers. Most of these devices where huge and can produce the same voice as the 80’s cartridge devices, but in the 90’s all this changed due that CPU speed increased drastically and software could be used.
Back to the Currah Speech device the only difference between Machine versions where the rom commands and the allophone chip decoder. The commodore 64 version was easier to program since you can use the commands say, kon, and koff in order to reproduce the voice. While other machines you had to put the phrases to say into a variable string. The advantages of these types of cartridges is that the CPU and Sound chips are not used to reproduce the voice synthesis, while other software based speech, the CPU, and Sound card are constantly used so other operations have to wait until the voice data has been processed completely. Despite all this the cartridge was not so popular and with its price tag of $50 was considered high at the time.
Another drawback for the Commodore 64 was that you could only connect it through a TV and not to a monitor, as the cartridge has a lead to connect it through the video port to use the audio in of the Commodore 64. There was a work around for this but you had to spend another $15 for a splitter cable to use both the monitor and the cartridge. It’s true you could do it yourself for a cheaper price but at that time it was all new and nobody wanted to damage their computers. During the following years Currah reduced the price but there were other companies that produced other types of cartridges which were capable of recording human voice and music which the Currah cartridge was not able to do.
Today it is very popular with collectors especially the C64 version, but unfortunately not all of them are complete with instructions posters, manuals and most of them can be sold with damaged chips inside. Usually damaged cartridges 99% of the time is the SP-0256-AL2 chip which is still available, but if you find one that the damage is within the other 2 chips then parts will be very difficult to find especially the rom chip.