Tavish Design Minotaur Quick-start Manual And Owner's Manual - 3 D
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3 D
ESCRIPTION AND
S
PECIFICATIONS
The Minotaur is an amplifier with a direct-coupled vacuum-tube signal path, direct-coupled to a
transistor output stage. The design uses 7 vacuum tubes to handle the input, voltage gain, and driver
stages of the amplifier. The high-bias class-AB (linear, non-switching) output stage uses the well-
regarded MJL3281 and MJL1302 devices in a modified Sziklai configuration for outstanding linearity, and
it operates in pure class-A up to either 1W or 5 W per channel (see Section 4.1). The vacuum tubes are
powered from regulated high voltage and heater supplies to achieve minimum noise and operating drift.
The Minotaur is configured as a stereo integrated amplifier; it features instrument-like construction with
high-quality components and connectors throughout. For user convenience, it has a wireless remote
control (no need to point, works anywhere in the house), using a classic ALPS “blue velvet” motorized
potentiometer for volume control and OMRON low-signal relays for source selection.
The Minotaur takes advantage of both the linear, high-voltage-swing capability of vacuum tubes and the
high-current-delivery capability of transistors, allowing the tubes and transistors to do what each does
best. And, the Minotaur is direct-coupled from the input stage to the output, avoiding the use of
coupling capacitors at high-signal levels, where they can cause slow recovery from overload transients.
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The Minotaur is one of very few hybrids on the market to directly couple the tubes to the transistors.
In developing the Minotaur, particular attention was paid both to achieving very low distortion, and also
to the character of whatever small distortion was produced; below clipping, the distortion spectrum is
dominated by the single-ended 12BH7 vacuum tube driver stage and is predominantly second harmonic.
The system microcontroller monitors temperature, offset, and bias conditions, and alerts the user to the
need for eventual tube replacement (see Sections 4.4 and 5.2). Output current limiting, output offset
detection, and advanced safe-operating-area protection for the output transistors result in a highly
reliable amplifier, without any of the maintenance issues sometimes associated with high power tube
amps.
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A coupling capacitor is used at the amplifier input to prevent a DC offset from the signal source from being
applied to the amplifier.