6977 Tubes are a type of electron tube used in high-end audio equipment for several decades. They were introduced in 1961 by the RCA Corporation and were very popular with guitar amp manufacturers due to their relatively low distortion and excellent sound reproduction. 6977 Tubes are larger than other audio-grade tubes and contain a dual filament structure which helps them handle larger signal levels while providing a higher signal to noise ratio. 6977 Tubes are still being used in high-end audio setups, and many guitarists prefer them due to their ability to handle large signal levels as well as their natural-sounding signal.