Passlabs X150.5 Stereo Power Amplifier
The perfect no nonsense power amplifier. Balanced or single ended input.
The Point 5 Series represented a highpoint in the evolution of Pass Labs amplifiers. At the time the X.5 and XA.5 models were introduced, Pass Labs R&D laboratories had accumulated several significant performance improvements and were eager for their customers to experience it.
Two hallmarks of Point 5 Series amplifiers are improved power and control. They possess the dynamic range to do justice to the most advanced
recordings, the elegance to retrieve the most sensitive microdynamics loudspeakers offer, and the ability to move easily from total silence to explosive
transients without losing information. Pass Labs achieved these ends through a number of refinements. For example, they replaced the input differential MOSFETs on their amplifiers with the same JFETs they use for the input devices on the MM and MC phono stages.
The JFETs deliver less noise, higher input impedances, and greater linearity. They operate self-biased within a symmetric quad topology in which each device is cascoded and level-shifted to form the full voltage gain stage of the amplifier. Also added, are more power-output devices, especially complementary power MOSFETs that provide more current and better power handling and linearity.
In addition, our Point 5 output stages use a heavy bias current for push-pull, Class-A operation to a large portion of the rated power as well as a bias source for single-ended Class-A operation at low wattages. A newly developed bias generator is installed to eliminate three sources of bias-current variation in the output stage.
The new bias circuit also allows approximately 20 percent greater power output for a given supply voltage. Of critical importance, the Point 5 circuits resulted in lower distortion at all power levels and into all types of loads, particularly in the critical audio mid-range.
Finally, Point 5 Series amplifiers employ the acclaimed Supersymmetry™ circuit developed by Nelson Pass, which improves performance by cancelling distortion and noise. As a result, X.5 and XA.5 amplifiers embody significant improvements over their classic Pass Labs predecessors, while delivering the warmth, sweetness, depth and space that are the distinguishing characteristics of outstanding audio products. They also possess greater reliability. These amplifiers are harder to break and easier to repair if they ever do.