Evolution Line Preamplifier

The Preamplifier servers two purposes: to amplify the incoming signal from a source and to switch among the sources. The less internal noise a preamp generates the better it can achieve these goals. A key design criterion for the Doshi Evolution Preamplifier was to take the already low noise floor of the V3 Preamplifier and reduce it by a whole order of magnitude.

A significant portion of the noise reduction can be attributed to the Evolution’s new power supply that features high stability and ultra-low noise regulation of the B+ voltages, revised design of the transformer volume control and revised, and an improved output transformer.

The Evolution Preamplifier introduces new super-premium parts including Copper Matrix capacitors from ClarityCap and TKD resistors in the signal path. Vibrations are further reduced by a new aluminum constrained layer top plate. The Evolution Preamplifier has 4 inputs, each of which can be RCA or XLR, and two outputs, also RCA or XLR. A Home Theater Bypass is standard. The included remote control has discrete input selection, volume, and mute.

The color options are natural anodized aluminum or black finish.

Details

The Doshi philosophy can be expressed in one word: balance. A balance of classical and cutting-edge technologies, of eastern and western sensibilities, of professional and residential design strengths. Nowhere is this sense of balance more evident than in the Doshi 3.0 Line Preamplifier.

Designed for residential use, The Doshi Line Preamplifier nonetheless takes advantage of sophisticated techniques developed for the recording industry. Based upon legendary studio hardware including Pultec EQs and Universal Audio Compressors, Doshi has developed a transformer-coupled volume control, a technology which helps the Line Preamplifier achieve the highest performance possible. The Doshi circuit provides differential, fully isolated floating outputs, thereby eliminating the possibility of ground loops at input or output, and assures absolute freedom from ground noise: an especially important consideration with digital sources.

To meet Doshi’s mandate of design simplicity, Doshi employ a single gain stage, with one ECC99 Dual-Triode Vacuum Tube per channel: the first triode provides gain while the second is used as a “Follower” to minimize output impedance. Thanks to their rigorous circuit design, the Doshi Line Preamplifier offers zero negative feedback, low output impedance and can drive any cable and amplifier load.

The Doshi Linestage includes four differential inputs, each of which can be outfitted with XLR or RCA connectors, tailored to its owner’s needs (Two XLR and Two RCA are Standard). Inputs are relay-switched into a transformer which provides 31 precision steps. Home Theater Bypass is also provided, further augmenting versatility. Two sets of differential isolated outputs—also specified as RCA or XLR to the customer’s desires— and a 12V on/off Trigger complete this preamp’s comprehensive connectivity. Naturally, all functions of the Doshi Line Preamplifier have been placed under the control of an elegantly styled, machined aluminum remote handset.

Behind its sculpted aluminum faceplate, the chassis of the Line Preamplifier incorporates Doshi’s Three Stage Decoupling (TM) technology to virtually eliminate the influence of both external and internal resonances upon the circuits’ performance. Inside the chassis, critical audio circuits are point-to-point wired and mounted on an acoustically isolated sub-chassis. The entire chassis is suspended from a ½“ thick slab of laser-cut, DuPont Corian which, in turn, floats upon four vibration absorbing feet that are mechanically decoupled from the chassis. While many competitors build their enclosures from mild steel and aluminum, Doshi uses extremely strong 14 gauge stainless steel to create a chassis that is mechanically and electrically inert; as a result, these components provide an ideal foundation for performance.

As befits a state-of-the-art product, the Doshi Line Preamplifier includes an oversized power supply housed in a discrete, resonance-controlled chassis. Connected to the Preamplifier via a custom made cable, designed to Doshi’s proprietary specifications, the Power Supply includes a custom-built transformer. Manufactured by Toroid, this transformer has been massively over-specified to prevent resonances that occur when a transformer is run at full capacity. Avant-garde design techniques prevent modulation in the power supply.

The Doshi Line Preamplifier represents the highest level of performance ever achieved in an audio linestage. The product of timeless circuit designs, executed with the finest component parts and uncompromising build quality, the Doshi Line Preamplifier represents a lifetime investment in musical enjoyment.

Doshi EVO Line Preamplifier Manual