TEA2 Phono Equalization Preamplifier The TEA-2 triode equalization amplifier is a vacuum-tube phono stage offering an extraordinary degree of musical accuracy at a moderate price. The audio circuit of the TEA-2 is comprised of two cascaded single-ended triode amplifiers. The circuit is a zero-feedback design, to eliminate the temporal inaccuracies that negative feedback introduces. RIAA equalization is established by a passive network between the two gain stages. This network has been carefully designed and has been implemented with precision (1% tolerance) parts to precisely track the prescribed RIAA equalization curve assuring absolute tonal accuracy. Careful implementation of this fundamentally simple circuit results in extremely wide bandwidth, and low distortion, without resorting to negative feedback. A high-current MOSFET buffer stage follows the second gain stage to achieve a low output impedance (less than 200 Ohms). |