conrad-johnson classic phono tube preamplifier

CLASSIC Phono Equalization Preamplifier

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.

The CLASSIC SE takes the parts quality up a notch further.

Twelve of the most critical resistors in the audio circuit are upgraded to laser-trimmed metal foil resistors. Seventeen capacitors are upgraded to CJD Teflon capacitors (chosen for their exceptionally low “memory” characteristic), including intra-stage coupling capacitors and critical “bypass” capacitors.

Thoughtful engineering, specification of quality component parts, and painstaking care in production are clearly on display in each of the CLASSIC models.

conrad-johnson Classic Phono Preamp back angle

Classic Phono

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
Owner’s Manual