Ranieri Audio Labs has announced the release of the Varieta preamplifier, a directly heated triode (DHT) vacuum tube amplifier designed to support a wide selection of 4-pin triodes. Built for users interested in tube experimentation, the Varieta accepts a broad range of tube types, including:
300B, 2A3/6A3, 12A/201A, 26, 30, 31, 45, 50, 71A, 801A/10Y, 275A/252A, 245, and 842/VT52.
This level of compatibility allows users to evaluate various tubes in the same system, comparing their differences in tonal characteristics, dynamics, and resolution without the need for dedicated hardware changes.
Simplified Tube Selection with Mechanical Switching
Central to the Varieta’s design is the Rotare selector, a rotary dial located on the top panel. This mechanical switch enables users to select the installed tube type, reconfiguring the circuit accordingly. Electrical parameters are automatically adjusted to match each tube’s requirements, eliminating the need for manual recalibration or circuit modification. The process is intended to reduce user error and streamline the experience of tube substitution.
Technical Design Overview
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Zero-Feedback Circuit Topology: The Varieta operates using a two-stage, zero-feedback topology with transformer-coupled outputs. This approach avoids the introduction of global feedback into the audio path, preserving each tube’s natural behavior.
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Low-Noise Operation: The internal circuit layout and component choices are aimed at minimizing noise and electromagnetic interference, enabling clearer signal transmission and lower background levels.
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Auto-Biasing: The circuit includes an automatic bias mechanism, removing the need for manual adjustment when changing tubes. This simplifies setup and ensures consistent performance across the supported tube range.
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Tube Rectification and Stabilized Power Supply: Power is delivered via a tube-rectified, linearly stabilized power supply. This configuration provides steady operation and prevents voltage fluctuation from impacting audio performance.
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Component Selection: The Varieta uses parts from established suppliers, including Lundahl (transformers), Caddock (resistors), Alps (potentiometers), and WIMA (capacitors). The selection is based on known electrical performance rather than brand recognition.
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Chassis and Build: The enclosure is machined from extruded 6061 aluminum and available in black or silver anodized finishes. The material provides mechanical strength and thermal stability without unnecessary design flourishes.
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Remote Control: Basic operational control is available via a handheld remote, allowing users to make adjustments without direct interaction with the main unit.
The Varieta is intended for experienced listeners and builders who are familiar with tube characteristics and appreciate the opportunity to evaluate different triode types in a controlled setting. While the system automates certain functions, understanding of tube behavior remains important for meaningful use.
