FROM WIKIPEDIA: The Fender Twin Reverb is an all-tube guitar amplifier with two 12″, 8 ohm speakers made by various suppliers. The more common speakers found in Fender Twin Reverbs include Jensen C12Ns, Oxford 12T6s, JBL D-120Fs (an upgrade at the factory), Utahs and, in later years, CTS and Eminence models. Some twins were fitted with EVM 12L variant speakers known as EVM 12Fs. Unlike most Electrovoice speakers, they were fitted with metal dustcovers like the JBL D-120Fs. The Twin Reverb is frequently shortened in conversation to ‘Fender Twin’ or simply ‘Twin’, though it shouldn’t be confused with the Tweed or Blonde era Twin amplifiers which had vastly different circuits and no reverb. The Fender Twin Reverb is considered a standard model for players seeking a clean sound, and it is especially known for the quality of its built-in spring reverb. All Twin Reverbs feature a solid state rectifier.