BRAND: Pass Labs

SERIES: HPA-1 Power amplifiers
TYPE: Power Amplifier, Lifestyle

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. The amplifier was highly acclaimed, and was called the “Amplifier of the Decade” in Stereophile magazine.

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.

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Gain (dB)   
8 dB

Power Consumption(W)
6 Output

Power into 20 ohms 
3500 mW

Output Power into 300 ohms
200 mW

Frequency Response 10hz -100k
-1 dB

THD + Noise   
< 0.005 at 1V out

Input Impedance  
50K Ohm

Output Impedance  
< 2 ohms

Dimensions (W x H x D)  
4.5 x 11 x 13 nich

Unit Weight (LBS)