This is the schematic diagram of Electro-Harmonix Small Stone Phaser guitar effect pedal. The Small Stone is somewhat special in applying Operational Transconductance Amplifiers (OTA”s) for phase shift stages rather of opamps with variable resistors. All of the IC”s are house marked EH1048, but could be replaced with CA3094 that is a combination of an OTA equal with the CA3080 as well as a darlington emitter follower. Later Small Stones put to use slightly different circuits, but all applied the OTA.
Electro-Harmonix is a New York-based company that makes high-end electronic audio processors and sells rebranded vacuum tubes. The company was founded by Mike Matthews in 1968. It is best known for a series of popular guitar effects pedals introduced in the 1970s and 1990s.
Download the schematic diagram of Electro-Harmonix Small Stone Phaser Guitar Effect from below link: