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Usher P-307A MKII Preamplifier
November 26, 2022Class A Usher R-1.5 Stereo Amplifier
A High Performer at Any Price!
The Usher R-1.5 stereo amplifier is built like a tank. Its utilitarian industrial design bears a striking resemblance to the Threshold 300 Stasis designed by audio guru Nelson Pass, which should come as no surprise.
In 1972 Usher Audio’s owner and head engineer Lien-Shui Tsai built the first Usher R-1.5 amplifier as a copy of the e300 Stasis amplifier whose patent expired and its designer, the venerated Nelson Pass, had welcomed others to use it. It began as a fun project, however it soon became a hit with customers and eventually many audio enthusiasts throughout Taiwan became proud owners of this phenomenal amplifier.
The R-1.5 amplifier is designed to drive any loudspeaker, producing warm, “tube like” sound quality. It has been constructed with premium parts, including metal film resistors and film capacitors, reinforcing Usher’s reputation for high-quality manufacturing. High-power bipolar transistors, designed by Motorola, can handle sophisticated power and current requirements. And its massive AC power transformer works with a high-capacitive filtering system for the purest sound. Other features include Burrow-Brown OPA2134P Sound Plus Series op amps, bridging switch for mono block operation, terminals that accept both banana plugs and spades, optional balanced inputs and large handles on the front and rear panel.
Massive heat sinks adorn the sides, and rows of vents line the top. At the rear are two more large handles, RCA (unbalanced) and XLR (balanced) inputs, a sliding selector switch for Balanced or Normal (Unbalanced), a sliding selector switch labeled “Operating Mode” to select Bridged Mode (Mono) or Normal Mode (Stereo), right and left speaker cord outlets, an IEC connector inlet, and an amp fuse port. Underneath, four sturdy legs provide ample support.
Technical data
- 8 Ohm: 150W(ch)
- 4 Ohm: 260W(ch)
- damping factor: >175 (single ended)
- circumgyration: >40V / uS
- power supply (4 Ohm): >16A
- transient power supply: >75A
- S/N ratio: 100 dB
- frequency (20Hz-20kHz): – 0.25dB
- (20Hz-100kHz): – 3dB
- weight: 37 kgs
- dimension (w x d x h ): 48 cm x 48 cm x 22.5 cm