My EEG amplifier was a 'home brew' - a commercial machine would be far too expensive. It's not too difficult to design if you're an [electronic] engineer, the main issue is safety as it must be totally isolated from any mains powered equipment - this also helps with noise rejection as the signals are very small.

I like the idea of using hypnosis to achieve LD/SD, I was wondering if would be possible to combine this with biofeedback, i.e. achieve a hypnotic state in a feedback loop with a computer - this would need to play wav files, or flash images/messages on a screen to induce a hypnotic state - since it isn't really possible for all the people participating in such an experiment to each have a [human] hypnotherapist with them. Anyone done anything along these lines? Is inducing a hypnotic state possible without a human hypnotherapist?