Nelson Pass & Linear Systems: The B1 Buffer Preamp
- JC - Linear Systems
- Sep 25
- 3 min read
Few names in audio design inspire as much respect as Nelson Pass. For decades, Nelson has pushed the boundaries of amplifier and preamp design with simple, elegant circuits that deliver extraordinary sound quality. His work has shaped the way audiophiles, DIY builders, and even professional engineers think about high-end audio.
One of his most enduring contributions is the B1 Buffer Preamp. At first glance, it looks deceptively simple: a unity-gain buffer with just a handful of components. But simplicity is part of the magic. The B1’s performance comes directly from the quality of the devices at its heart — JFETs, chosen for their unmatched noise and linearity characteristics.
Why JFETs?
JFETs are ideal for front-end and buffer applications because of their:
High input impedance – preventing loading on delicate audio sources.
Low output impedance – ensuring strong, stable drive into power amps.
Low noise and excellent linearity – crucial for preserving the subtle details in music.
Nelson Pass has long relied on Linear Systems’ JFETs in this role. In the B1, the complementary pair of N-channel and P-channel JFETs provides transparency and neutrality — qualities that have made the circuit famous in the audio DIY community.
Linear Systems Inside
The classic B1 buffer used the 2SK170 and 2SJ74, but as those parts became scarce, Nelson and the DIY community turned to Linear Systems’ equivalents:
LSK170 – N-channel JFET, ultra-low noise, high transconductance, widely used in audio and precision instrumentation.
LSJ74 – P-channel complement, designed as a low-noise, high-performance match to the LSK170.
LSK389 – dual, monolithic version of the LSK170, offering superb device matching and thermal tracking in a single package.
By integrating these parts, the B1 achieves a combination of clarity, drive, and quiet backgrounds that has made it a reference design for both commercial and DIY preamps.
Design Philosophy: Simple but Brilliant
The B1 isn’t about flashy complexity or an endless parts list. It’s about getting the fundamentals right. Nelson has often said that he prefers simple circuits with the best possible devices, and the B1 reflects that philosophy.
With Linear Systems’ JFETs, the B1 offers:
Musical transparency – nothing added, nothing taken away.
Reliability and stability – thanks to tightly controlled device specifications.
Enduring accessibility – DIYers and builders around the world continue to build and enjoy this design.
A Partnership Built on Trust
Nelson Pass has been a longtime friend of Linear Systems, and his decision to use our JFETs reflects a deep trust in their performance and consistency. From phono stages to amplifiers to buffers like the B1, Linear Systems devices have become a staple in Pass designs.
That legacy continues today, as both professional audio engineers and hobbyists choose LSK170, LSJ74, and LSK389 as drop-in solutions for their high-end audio projects.
Learn More & Build It Yourself
The full B1 Buffer schematic and project description are available directly from Nelson Pass at PassDIY – B1 Buffer.
Whether you’re an audiophile, a designer, or a curious DIY builder, the B1 is a perfect example of how great devices make great circuits possible.
At Linear Systems, we’re proud to see our JFETs featured at the core of such a beloved design.
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