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The Sound Station |
My 20 year experience with Nelson Pass's products has been invaluable. He is such a great designer. He shares his knowledge with all and is a asset to our industry. He has left a great legacy of products like Threshold, Alaph, X series, Rushmore and many unclaimed designs used by others in kits and hobby projects. Thank you Nelson! |

XA.5 SERIES - Class A Models
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X.5 SERIES - high bias AB |
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Pass labs continues to improve its power amplifiers. After five years, these acquired enough mass to warrant a change in designation and the X.5 series was announced. The improvements are: |
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Cascode JFET Symmetric front end – input differential MOSFETs have been replaced by the same JFETs we use for the input devices on our MM and MC phono stages. They have very much less noise, higher input impedance, and greater linearity. They operate self-biased in a symmetric quad topology, each device cascoded and level shifted to form the full voltage gain stage of the amplifier. |
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More power output devices – Greater quantities of matched complementary power Mosfets operated as followers, giving more current and power handling, and also improved linearity.
Single-ended Class A bias – The output stage not only uses a heavy bias current for push-pull Class A operation to a large portion of the rated power, but also has a single-ended bias source for single-ended Class A at low wattage. |
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New bias circuit – A newly developed bias generator has eliminated three sources of variation in bias current in the output stage. It also allows approximately 20% greater power output for a given supply voltage. |
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Improved power supplies – The power supplies have been given greater storage capacitance, larger / quieter power transformers, fast recovery rectifiers (twice as many), and improved harmonic filtering in both the primary and secondary supply circuits. |
Other links
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Better layout – All portions of the amplifier circuitry have been refined with respect to wiring and circuit board layout so as to achieve lower noise and distortion and greater reliability and serviceability. |
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INTEGRATED Amps |
INT-150 |
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In performance, the INT-150 boasts an excellent dynamic range and fast response. Rated at 150 watts-per-channel into 8 ohms, and 300 watts into 4 ohms, it moves easily from black background to explosive transients, then back again, adding realism and authenticity to recorded materials. | ||||||
| It performs with authority and stability regardless of loudspeaker load. Smooth and transparent, the INT-150 provides clean, expansive sound at an affordable price. | |||||||
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PREAMPS |
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The new XP series pre-amplifiers are more true to state of the art recordings than our previous product. Highly dynamic passages typically have more weight; bass lines are more clearly, cleanly, and accurately delineated. |
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Instruments and voice are presented in a more refined spatial envelope, and with better spectral balance. Fine nuances and details become apparent -- even in loud and highly complex musical passages. | ||||||
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The XP-15 is a single chassis successor to Pass Labs’s award-winning Xono phono-stage. It features lower noise levels, greater resolution, better base control and an attractive single-chassis design. It’s superb construction only suggests the quality of the listening experience it delivers — a lush, smooth sound with a wide stage and firm bass. | ||||||
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The XP-15 is easy to set up and a pleasure to use, especially given that the best of today’s vinyl is significantly better than what was available when vinyl was the mass-market audio media of choice |
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The new SR1 is Pass Labs’ second loudspeaker, following the Rushmore, its exceptionally dynamic introductory speaker. The new SR1, a four-way floor standing system, is equally uncompromising. Its highly refined sound stage, deep awareness of micro-detail, and effortless dynamics deliver superb, accurate musical reproduction. |
SPEAKERS SR-1 |
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The SR1’s drivers are the best available, and employ Nextel-coated cones and a Crescendo tweeter from the renowned Seas of Norway. They present the best combination of low distortion, high dynamics, and predictable performance. It takes a minimum of four sizes of these drivers to span the SR1’s 10-octave audio range without significantly leaving the “piston” region. The SR1 uses dual enclosures. A large bass enclosure with ten-inch and eight-inch drivers handles the bottom four octaves, and an adjustable smaller enclosure carries the mid range and the tweeter. The Seas of Norway drivers are complemented by a set of crossovers to elicit the drivers’ best performance. |
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