Pass Labs is one of the most dependable brand names when it comes to high-end audio systems. For years the brand has been recognized by audiophiles throughout the world as equipment that delivers clear and consistent quality in music.

What else to know about the Aleph 1.2?

"The Aleph 1.2 is the most powerful of the newest generation of amplifiers from Pass Labs. This design results from my commitment to create the best sounding product, a simple circuit having the most natural characteristic. The Aleph 1.2 integrates power Mosfet devices and pure single ended Class A operation in a simple two-gain-stage topology with the sole purpose of recreating subjectively natural sound. "The Aleph 1.2 is unique in a number of ways: Unlike the early Aleph amplifiers, it operates in pure single-ended mode over its entire operating region, and does not incorporate a “pull” stage for additional current beyond its bias point. When the single-ended output Mosfets (two groups of twelve in parallel) reach cutoff, the amplifier clips. "Most amplifiers on the market have between five and eight gain stages in series between the input and the output. The Aleph 1.2 has but two, and enjoys a very direct path from input to output, further enhancing the purity of the circuit and the resulting sound. Early Aleph amplifiers have three gain stages. "The output stage of the Aleph 1.2 is a unique blend of traditional design and innovation addressing the unique requirements of loudspeakers. Previous methods of loading the output stage have used networks consisting of resistors, coils, transformers, and active current sources, all of which offer an optimal load line based on a resistive load. The Aleph 1.2 has a current source topology which optimizes performance for a wide range of impedance and reactance in the load, improving all aspects of performance into real loudspeakers. Pass Labs has a US patent pending on this output stage topology." - Nelson Pass

Brief History of Pass Labs

Pass Laboratories, Inc. was founded in 1991 by Nelson Pass. Operating out of his shop at home, Pass developed prototypes of a single-ended Class A amplifier design. At the same time, he and Mike Burley were constructing an in-house machine shop with three home-built CNC milling machines with which to produce the amplifiers when the design was finished.

The first product, the Aleph 0, shipped in 1992. It was a mono-block design rated at 70 watts into 8 ohms, and was unique in using three gain stages of power Mosfets including a push-pull output stage biased by a big constant current source. The amplifier operated as single-ended Class A up to its 70 watt rating and in push pull Class A at higher wattage.

At this time, Nelson hired his next-door neighbor, Elena Tong, to help with producing the amplifiers, and she manages much of the company to this day. A stereo version called the Aleph 0s followed after, along with a preamp called the Aleph P. A larger version of the Aleph 0 called the Aleph 1 shipped the following year, and was a mono-block rated at 150 watts.

Other Pass Labs Products We Often Buy

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The following images show actual Pass Labs equipment purchased by StereoBuyers.