TEA1 Series 2 Phono Preamplifier
The TEA1 Series 2 triode equalization amplifier is a stand-alone vacuum-tube phono stage designed to satisfy the expectations of the most demanding music lovers.
The TEA1s2 features a zero loop feedback circuit with passive RIAA equalization. It offers two phono inputs, one with switch selectable resistive and capacitive loading allowing the user to fine-tune performance to the chosen phono cartridge. The other input is fitted with premium wide-bandwidth audio transformers installed on the PHONO 1 input to provide the higher gain and very low noise required by low output moving coil cartridges. Designed to precisely track the prescribed RIAA equalization curve, the TEA-1s2 assures absolute tonal accuracy. The low-gain audio circuit of the TEA-1s2 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. Careful implementation of this fundamentally simple circuit results in extremely wide bandwidth and low distortion, without resorting to negative feedback.
The ideal dc power supply circuit is simply a zero impedance path to ground.
Any deviation from this ideal is fully reflected in the audio circuits. Thus the power supplies are as important to audio performance as the audio circuits and must be accorded equal attention in design. In the TEA-1s2, each stage has its own discrete regulated DC power supply. These power supplies have been carefully designed for minimum impedance, even at the highest audio frequencies, to prevent the power supplies from degrading music reproduction.
The TEA1s2 is optionally available as the TEA1s2b with the step-up transformers deleted. This version of the TEA1s2 has two direct inputs, one with variable loading and one with fixed loading.
The full potential of any circuit design can only be realized if executed with the highest quality parts.
The audio circuits of the TEA-1s2 use only conrad-johnson’s proprietary Teflon capacitors. In the power supplies, all capacitors are polypropylene or Teflon – there are no electrolytic capacitors anywhere in the audio circuits or their dc power supplies. The audio circuits and related power supplies both use high-precision laser trimmed metal-foil resistors, designed for ultra-low inductance. All parts in the RIAA compensation network are 1% tolerance, to assure precise tracking of the RIAA curve. Input and output connectors are gold-plated, machined oxygen free copper. Even the hookup wiring has been carefully selected for optimal audio performance. Thoughtful engineering, specification of the finest available component parts, and painstaking care taken in production make the TEA-1s2 a phono equalization preamplifier without peer in music reproduction.