In this Letter, we present an experimental demonstration of an all-fiber ring Mamyshev oscillator (MO) that delivers a 300 mW optical power at a repetition rate of 45 MHz. Numerical design has shown that more than 70 MHz repetition rate is achievable in a ring cavity configuration using standard step-index fibers and components. Interest of WDM type filtering on pulse duration is especially shown. This demonstration of a high repetition rate ring Mamyshev oscillator working with the simplest transmission filter paves the way to very simple and cost-effective all-standard-PM-fiber Mamyshev oscillators.