When a dynamically varying signal is applied to the input of the 905, the output will consist of a series of closely spaced echoes, the subjective effect of which is similar to that of reverberation of sound. If a small amount of "echo signal" is mixed with a larger amount of "direct signal" (Reverberation Control set slightly clockwise), the effect of a typical concert hall is obtained. If the echo signal only is passed (Reverberation Control is set fully clockwise), an exaggerated echo suggesting a cave is obtained. The relative amount of echo signal and direct signal can be continuously changed from 100% direct signal to 100% echo signal.

Specifications:
Power: +12 (25mA), -12 (25mA)
Depth: 40 mm
Doepfer compatible