Introduced November 1990, SE in December 1992
The Evolution 20 was the only preamp made by conrad johnson to bear the Evolution Series name. The Evolution Series were products of a unique nature that fit between the standard conrad-johnson product line and the exclusive Premier product line.
The EV20 was actually two mono preamplifiers with separate power supplies combined into a single stereo package sharing only the chassis, ac line cord, and power transformer. Coupling between channels is thereby held to a minimum. The circuit was an end-to-end zero feedback design derived directly from that of the flagship Premier Seven preamplifier, with minor compromises needed to fit it all into a single chassis (in contrast to the Premier Seven's four).
Built like a battleship, the EV20's superior external construction and quality feel of controls are immediately apparent. The famous "cjd" capacitors and high-precision laser trimmed metal-foil resistors are used throughout. The volume control is a 23-position switch selecting among 23 pairs of resistors never more than a single-pair of resistors are inserted in the signal path by this control. The balance control is an 11 position switch that is electrically out of the circuit in the centered position.
The EV20 had outstanding dynamic range and extended low bass along with the depth and spatial characteristics for which conrad-johnson is noted, making the EV20 one of the finest preamps available at the time.
Features: Inputs / Outputs one phono, tuner, auxiliary, CD, monitor and recording facilities for two tape decks with dubbing from Tape 1 to Tape 2. One pair power amplifier (RCA main) outputs. Controls: Selector, record, balance, volume, & power.
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Specifications:
Gain: 40 dB Phono Stage
Line Stage 25 dB
Distortion: less than .5% THD or IMD at 1.0 V output
Response: bandpass 2Hz to more than 100kHz
RIAA Equalization +/- 0.25 dB (20Hz to 20KHz)
S/N Ratio: Phono Inputs 80 dB below 10 mV input
Line Stage 94 dB below 2.5 volt output
Phase Response: Line Stage - phase inverting, Phono Stage phase correct
Mechanical: 19" X 7" x 15 _" weight 37lbs.