Фонокорректоры — Doshi Audio Evolution Phono Preamplifier

The Evolution Phono Preamplifier is a valve phono stage from Doshi Audio, the American company founded by Nick Doshi, a former recording engineer, nearly two decades ago. The power supply lives in its own box, joined by an umbilical. Doshi's philosophy is to use simple circuitry with as little feedback as possible, choosing valves or transistors wherever each works best.

Key specs that matter

Inputs can be configured as 2 MM and 1 MC or 2 MC and 1 MM, and in the standard layout the MM inputs load at 10 kohm and 47 kohm and the MC input is differential, on RCA or XLR. MM gain is about 50 to 54 dB, and the MC section adds about 20 dB, jumper adjustable to 14 dB, for a total of up to 74 dB. Outputs are RCA and XLR, quasi-balanced or transformer-balanced. Signal-to-noise is at least 80 dB below 1 V unweighted on the MC input. The SE version uses six valves per channel from the 12AX7, 12AT7 and 12DW7 types. Power consumption is 29 W, and the preamplifier and supply together weigh about 15.4 kg.

Engineering and use context

The circuit uses zero feedback and passive RIAA equalisation. The MC section uses a JFET head amplifier followed by a step-down, a 2 to 1 voltage step-down giving a 4 to 1 impedance step-down, so the stage has a very low output impedance when driving the capacitive load presented by the valve's Miller capacitance. Loading can be changed by remote control on the fly, and two MC load settings can be stored in memory. The power supply is a new design with high-stability regulation, a low noise floor and passive power correction, housed in its own chassis to isolate it from the audio circuits. Components include AudioCapX and ClarityCap CMR capacitors and point-to-point wiring. Finishes are natural or black anodised aluminium, and the main audio board holding the valves is suspended from the top of the chassis with vibration isolation. A mono switch is available as an option, and other playback equalisation curves can be added. The SE version adds front-panel loading and gain controls, a 6 dB gain reduction switch and a special umbilical cord.

Pairing

With its high total gain, the Evolution Phono suits low-output MC cartridges, while a second MM input can take an external step-up transformer. The XLR outputs connect to balanced preamplifiers such as Doshi's own Evolution Line.

Alternatives

Doshi Audio has no other phono preamplifier, and the SE version is an upgraded form of this model.