Doshi Audio Evolution Stereo

Nick Doshi is cautiously reserved when he talks about his amplifiers, preferring to let the products speak for themselves.

- KEN MICALLEF

At every show I've heard them at, from Chicago to DC to Munich, they have done exactly that: Every system I've heard featuring a Doshi amp has delivered great sound. When I pressed him as to why, he just smiled.

So it was with a little trepidation that I asked to review the hybrid Doshi Audio Evolution Stereo Amplifier ($24,995), a push-pull, hybrid solid state/tube amplifier that operates its first 50Wpc in class-A into 5 ohms, up to 65Wpc in class-AB.

The amp exhibits the best qualities of a triode, Doshi insisted.

I asked Nick Doshi about this. engineer—“to show how a 300B push-pull amp should really be done,” Nick answered in an email. “It used 8B output transformers, which piqued my interest. I did some research and saw the similarities in the curves and tried an experiment involving a set of separate screen windings to deliver power from the screens of an EL34/6CA7 tube.”

Continuing the narrative from the Doshi Audio site: “Employing an extremely expensive output transformer custom-designed to Doshi's specifications, a discrete, tertiary transformer winding is connected directly to the grids of each output tube. As a result, when used at low power, the Doshi Stereo Amplifier provides sonic and electrical performance identical to a push-pull 300B amplifier!”

I've enjoyed many great triode-based amplifiers over the years. If Doshi’s claims about the sound of the Evolution Stereo Amplifier are accurate, I'm all in and all ears.

Class-AB stereo amplifiers are characterized by bias current that determines how much of the amplifier’s total power is delivered in class-A. The Doshi Evolution has not one but two notable transitions: It runs class-A up to 50W, and it acts like a triode amplifier for the first 10–12W.