Like many ampsandsound creations, the Zion, named for Zion National Park, began with a classic design known for its fidelity and absolute bandwidth from Stu Hegman of Harmon Kardon. Using the Citation V circuit as a touch point, we sought to find refinement through improved transformers and power supply optimizations.
The Citation V may appear as a simplified Citation II which serves as the bases of our Arch Push-Pull Flagship, but it still represents a high degree of sophistication and understanding of push pull amplification. It differs form the Arch with fewer gain-stages, shorter signal path and less feedback. This reduces output power, and linearity but adds a degree of humanity. Where the Arches are source accurate in reproduction without grain or sibilance, the Zions add a hint of warm while maintaining the all the detail and scale.
In building the Zions, we chose a chassis large enough with room for layout and acquisition without compromise. There are no space constraints or thermal considerations and as such, wire layout is optimized for performance not compactness. When looking at the power transformer, we sought to exceed the requirements of stereo amplifier with the capacity of our mono power transformer.
The degree of over specification was intentional to ensure greater regulation under normal operating conditions or at full use, in short the Zions like to be pushed and sound best being challenged. Vacuum tube rectification was chosen to completely remove any silicone from the amplifier and reduce opportunities for grain to creep into the signal. Careful attention was paid to the output transformers, as the original Freed transformers are simple in design, but phenomenally built.
This circuit demands exceptional transformers. The Zion transformers are quite special, achieving a bandwidth of 4hz to khz without consequential frequency response deviations. This wide bandwidth matches well with the circuit, which utilizes a 12BY7A Video Pentode capable of exceptionally wide frequency response. The Zion was also an early experiment in constructing a sophisticated amplifier on turret boards with point-to-point wiring, which most consider the standard-bearer for tube amplifier builds.
