Предусилители — Doshi Audio Evolution Tape Preamplifier

The Evolution Tape Preamplifier is a valve preamplifier from Doshi Audio for reel-to-reel tape playback, amplifying the signal from a tape machine and applying the playback equalisation. The model is part of the Evolution series, which builds on the earlier V3 design and also contains a line preamplifier, a phono preamplifier, a stereo power amplifier and monoblocks.

Key specs that matter

There is one stereo input, supplied with both RCA and XLR connectors, of which only one can be used at a time, and the input stage is differential and balanced. Maximum gain is 60 dB and can be reduced with internal jumpers. Doshi quotes noise at least 90 dB below 1 V unweighted and an output swing of more than 80 V peak to peak before clipping. Eight valves are fitted in total, three 12AT7 and one ECC99 in each channel. Power draw is 30 W, and the preamplifier and its power supply weigh 15.9 kg together. The casework comes in natural or black anodised aluminium.

Engineering and use context

NAB and IEC equalisation are handled by separate circuits. The Evolution power supply was redesigned around high-stability, low-noise B+ regulation with a combined series and shunt regulator, Schottky rectifiers and passive power factor correction, and Doshi states it is twice as quiet as the V3 supply. Across the series, filament voltages in the input section are regulated and a large high-voltage film capacitor feeds the plate supply. Signal coupling uses ClarityCap CMR capacitors, and circuit revisions target lower distortion and more linear gain while letting the valves run conservatively for longer life. The valves sit in machined Teflon sockets, and the chassis is 14-gauge stainless steel with a machined aluminium constrained-layer top plate that replaced the Corian tops of the V3 series. Level potentiometers use conductive plastic tracks. For comparison, the earlier V3.0 Tape Stage had a 150 ohm output impedance and a passive, low-impedance EQ network covering NAB, IEC and AES 30 ips playback.

Pairing

Two stereo outputs connect the stage to a line-level preamplifier or integrated amplifier - one direct XLR output and one transformer-coupled output that the buyer can specify with XLR or RCA sockets.

Alternatives

The Doshi Audio Evolution Line Preamplifier is the line-level model of the series, offering four inputs that can be ordered as RCA or XLR in any combination, up to 12 dB of gain and two ECC99 or 12BH7 valves.