TubeTone-2A — A 2W Single-Ended 6V6 Preamplifier + Amplifier

The above micro-power Amplifier utilizes a small Webtronics EM-02 Enclosure, a 160V heavily filtered power-supply, a DC Filament supply, a singele 12AX7 two-stage preamp, and a single 6V6 Power Tube to deliver ~2W into 8 ohms. It has a Drive control which sets the preamp drive level into the Power stage, a feedback Contour control, and a Side-Chain Output Level control which is tapped off a lifted cathode in the second preamp stage, inside the feedback contour loop.

The Contour control utilizes a specialized feedback arrangement to provide a tightening of tone of the single-ended stage for cleaner smoother characteristics, or when backed off allows for an open-loop single-ended overdrive tone.

Use of a 6V6 provides a very smooth and sweet overdrive tone when driven hard, or a silky smooth clean tone when backed off.

Micro-Power Amplifiers are typically utilized in studio-style signal chains to provide a nice final stage of tube-tone to the system. At 2W it is sufficient for driving a mic'ed speaker cab, or driving into a speaker-emulator load/attenuator and then into the mix. A Comp switch is placed on the output for use in direct drive applications without a speaker load. When engaged the Comp switch places a 30 ohm resistance across the speaker load taming the resonances at the output and tightening the voicing when driving high-Z loads directly. A Side-Chain output is also provided at odB gain levels nominally from the input yet retaining the tube voicing of both the preamp and power amp sections by being inside the contour loop.

Inputs of the Tubetone-2A are at standard line levels, requiring ~0dBu for full drive. The front panel input is designed for quick-patch checks and over-rides the rear input for testing and patching checks. The entire unit fits on a shelf within 2U rack height, and is ~8.25"W, ~5.8"D, and ~3.3"H. Both tubes are fully enclosed within the vented chassis enclosure for protection and ease of portability.

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