SPRING 905 - is an emulation of a legendary and classic Spring reverberation effect with Moogish kind of sound. In the 1960's Spring reverberations were a very new part of the guitar sound. This was a cheap and creative solution to mimic studio reverberation effects that were avaliable in studios.
Spring reverberation is based on a tank with a few springs between two electrical transducers. The input transducer shakes the springs in response to the electrical signal. The bigger the signal, the greater the movement of the springs. This signal coming from the springs is picked up by a second transducer, which converts the motion into a new signal that is then amplified and mixed with the original signal.
Bob Moog realized that this technology could be useful in creating space and realism for electronic music. This is how the 905™ reverberation modular unit was born. This ushered in a new age of space sounds of electronic music. In the original module, only one knob controlled the effect - the reverberation knob (mix of the dry/wet signals).