Conrad Johnson CLASSIC Phono Equalization Preamplifier

Please confirm preference of High Gain or Low Gain output version in the comments

The CLASSIC 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 CLASSIC is comprised of two cascaded single-ended triode amplifiers, and one single-ended triode cathode follower.

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 low-impedance vacuum-tube cathode follower stage follows the second gain stage to achieve a low output impedance (less than 700 Ohms).

In the CLASSIC, discrete regulated power supplies, carefully designed for minimum impedance, even at the highest audio frequencies, isolate the amplifier stages from the ac line and from each other to guarantee that power supply irregularities do not degrade the audio performance.

The CLASSIC is available in high-gain (53 dB) and low gain (40 dB) versions to match a wide range of modern phono cartridges.
The high gain version is recommended for use with cartridges with a rated output of 1.0 mV or below. The low gain version is best suited to higher output cartridges. Both versions offer switch selectable resistive loading allowing the user to fine-tune performance to the chosen phono cartridge.

The performance of any audio component is only as good as its component parts.
The audio circuits and the related regulated power supplies of the CLASSIC use polypropylene capacitors and precision metal film and metal foil resistors exclusively. All parts in the CLASSIC’s RIAA compensation network are 1%tolerance, to assure precise tracking of the RIAA curve. Input and output connectors and even hook-up wiring have been carefully selected for audio performance.

Specifications

High Gain: 53dB
Low Gain: 40dB
Overload HG: 10 mV
Overload LG: 50 mV
Hum and Noise HG <750uv
Hum and Noise LG <500uv
Phase: phase correct
Output Impedance: below 750 ohms
Mechanical
Dimensions: 13.625″D x 19″W x 3.625″H
Net Weight: 13 lb net