VAC Statement Phono Preamplifier

This VAC Statement dual mono triode vacuum tube phono (MM/MC, three gain modes, adjustable load, stereo/mono operation) preamplifier is designed for extreme applications. On the back panel there are two DC umbilical cords and large Amphenol aerospace connectors, a reminder of the massive dual mono power supply. There are inputs for four independent phone sources. In addition, each input may be of the conventional single-ended type or may be fully balanced.

Mechanical Design

The chassis is machined at VAC from high-grade, non-ferrous aluminum and processed through a series of plating steps. The resulting AICuNiCr chassis possesses superior RF rejection properties across a wide range of radio frequencies for greater resolution and subjectively blacker backgrounds. Similar care is taken around each of the six wideband audio transformers in each unit. In addition to the five regular line inputs, three of which may be used with balanced sources, there is also a fixed volume input for use as a slave in a multichannel home theater system, or with other sources that control their own level. The “cinema” source may also be balanced or single ended.

Electrical Design

The audio chassis is designed with distinct isolated sections dedicated to certain signal functions to prevent unwanted interactions among the circuits. Interconnecting wires are carefully routed and directed by spaced machined nonmetallic guides. The hand-wired vacuum tube audio circuit assemblies are bonded to massive brass loading plates, which in turn are isolation mounted to the main chassis for a very effective filter at audio frequencies. The avoidance of negative feedback and inclusion of input and output transformers confers the relatively unique trait of eliminating unwanted stray interactions between the source components and power amplifier, such as long chain interactions between their feedback loops which tend to coarsen the sound and flatten the sound stage.

Power Supply

A massive separate power supply is a dual mono design with substantial energy storage and high inherent regulation. Both resistive and inductive elements are used in concert with high-speed capacitor assemblies for the high voltage supplies, while active voltage stabilization is included in the four heater supplies and the 12-volt trigger supply.

Volume Control

The volume control is a massive one-pound multisection potentiometer some two inches long and nearly two inches in diameter, with machined brass shielding between the sections and against the outside world. This extraordinary part is critical in obtaining the highest fidelity in the world. A custom engineered VAC motor drive system allows the volume to be adjusted by remote control.  

Specification