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 are the specs for the X600.5?

Power output:
600 watts into 8Ω (mono)
Frequency response:
0Hz to 100kHz
Total harmonic distortion:
Damping factor:
30 dB
483 x 559 x 292mm

What else to know about the X600.5?

The Pass Laboratories TM X600.5 stereo amplifier embodies the de- sign technology and refinements of the “X” series amplifiers includ- ing extensions of the patented SupersymmetryTM circuit. Additionally selected refinements of the XA series amplifiers have been incorpo- rated into the X600.5 to significantly improve this products sonic performance in comparison to it’s immediate predecessor, the Pass LaboratoriesTM X600. The SupersymmetryTM circuit topology was granted a U.S. patent in 1994, and was the result of 19 years of effort by legendary analog designer and company founder Nelson Pass. The amplifier uses highly matched components in a classically simple single ended Class A circuit. The amplifier contains only two simple stages: the first is a balanced Class A gain stage. Its output drives a bank of high power devices operated as followers.

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

StereoBuyers has purchased tens of thousands worth Pass Labs brand equipment since 2014, with individual buys ranging from $100 to well over $50,000. If you are moving, ready to upgrade, or have Pass Labs equipment you do not or will not be using, why not contact us today to find out if it is worth good money?

If you are interested in selling your used Pass Labs equipment to us in the greater NYC area or Colorado, please click here to fill out a Free Quote Form and we will get back to you. If we agree on terms, we come to meet you where you want, and pay cash.

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