Software induced jitter is nonsense with any reasonable hardware (and by that I mean even cheap sound cards). But those who are worried about that should probably use DOS, or some special real-time operating system, as they will not get perfect software timing on a multi-tasking operating system that runs hundreds of threads, and is not designed for hard real-time applications. However, even the earliest Sound Blasters (those that only supported mono 8-bit audio) allowed for the use of DMA transfers and buffering, so that the actual audio playback is clocked by the hardware, and for the software the only requirement is to respond to the interrupts from the sound card fast enough that the buffer always gets filled with new audio data in time. Only on old 8-bit computers like the C64 was the software responsible for the timing of individual samples in digital playback. As long as the buffer does not underrun, the timing of filling it does not matter, and when it does, there are obvious breakups in the audio output.
Now of course some will worry about software affecting jitter through electrical interference, but interference always happens anyway, regardless of what program you are running (and a modern multi-tasking OS runs a lot of things all the time). The DAC or sound card should be designed to be insensitive enough to interference.
. The main advantage of this software is it allows you to easily evaluate different settings that would otherwise be much harder to test so you can decide whether it is worth finding a more permanent way of making these changes.
