FOR APPLE AND COMPATIBLE COMPUTERS
The DIGITAL SOUND SAMPLER from COMPUTER PARTS GALORE will allow you, through the use of a high speed analog to digital converter (AD7574),to digitally sample and save a microphone or line level input. Once the sample is taken it resides in the memory of your computer as a series of eight bit bytes in a continuous string of memory locations. It is then possible to reproduce the sample by outputting the stored data to the digital to analog converter (AD7428).
Now comes the truly exciting part. Just to be able to save and playback sounds on a computer is not all that exciting, anyone with a 30 dollar cassette recorder can do the same thing. The exciting part is that since the sound is encoded digitally and resides in a continuous string of bytes you can now use the computer to analyze, modify, shift, reverse, the sampled data or perform and other process you can dream up and program. Let's now look at the specs of the interface so we can get a better idea of what it's possibilities are.
The DIGITAL SOUND SAMPLER BOARD uses an 8-Bit sample which provides 256 steps of resolution. This theoretically will allow you 35-40 db of signal to noise ratio. The current software is set up to sample at sample rates of up to 30,000 + samples a second. It is a rule of thumb of sampling theory that you have to sample twice as fast as the highest frequency you wish to capture, So 30,000 samples gives you a 15K hertz ceiling. It is interesting to note that both the AD7574 and the AD7528 chips are capable of turning over in 15us (15 micro-seconds ) which means that they are capable of sampling up to 60,000 samples a second. But don't forget that since each sample is a byte that means that at 60,000 samples a second you would fill up the APPLE's 64K of memory very quickly. Also the APPLE and its compatible compatriots are not the fastest computers available today. We will leave it to some adventurous experimenters to see just how fast the APPLE can sample using exceptionally fast code. Also the advent of the new memory boards for the IIe versions of the machine should eliminate the first of the mentioned limitations.