An electronic circuit for adding the effects of reverberation to a high impedance signal produced from an external audio source such as a guitar pickup or a high impedance microphone. The electronic circuit comprises a reverberation effects circuit having pre-amplifier/driver and recovery amplifier sections and a spring reverberation device coupled thereinbetween and a reverberation effects bypass at the circuit's input, prior to switchably passing the audio signal into an input of the pre-amplifier/driver section which comprises a low impedance, high current output for input into the spring reverberation device having an output for passing a low impedance signal to the recovery amplifier section, which suitably serves in increasing the impedance of the signal to a predetermined level acceptable for input into an external sound device such as an amplifier having channel inputs and audio control capabilities, and a power supply circuit having means for switching between a dc volt source and an ac volt source and supplying .+-.9 volts to integrated circuits (ICs) included in the pre-amplifier/driver and recovery amplifier sections of the reverberation effects circuit.