The Sweet Spot- Nelson Pass 10/10/09 Introduction Every audiophile understands the concept of the “sweet spot”, that happy balance of conditions that elicits the best possible sound. It can be a particular listening spot, the best positioning of loudspeakers, or the fortuitous combination of components which complement each other perfectly.…

Audio distortion and feedback- Nelson Pass 11/1/08 Introduction Audiophiles seem to revel in minor controversies – vinyl vs CD's, tubes versus solid state, capacitor, wires, magic dots... and negative feedback. At one extreme, the position is that “feedback makes amplifiers perfect”. At the other extreme, “feedback is a menacing succubus…

Leaving Class A- The meters on our amplifiers are different. They reflect the current consumption of the amplifier, and when the amplifier is operating, they don’t go down to zero like the meters on other amplifiers. This is because the electrical current consumption of our circuits has a fairly high value at all times, a property called the…

Like Peanut Butter and Chocolate- Sometimes two designs complement each other so well that you are surprised they weren’t invented together. So it is with the X Super- Symmetric amplifier and the Aleph single-ended Class A output circuit. The Super-Symmetric “X” amplifier repeatedly demonstrates the possibilities for very high power, dramatic dynamic…

Power Supplies: Commentary for Consumers- (c) Nelson Pass, Pass Labs Intro: Electricity and Hydraulics Lots of people don't understand electricity, but they do understand plumbing. Hydraulics provides a good analogy in understanding basic electrical flow. Wire is a pipe. Water pressure is voltage. Water flow is electrical current. Lakes and storage tanks are capacitors.…

Trouble shooting for dummies- Rev 0.2, December 4, 2002 - (c) Kent English, Pass Labs Pre-Amplifiers Within the Pass Labs pre-amplifier family we typically see two installation errors, both involving cable issues. The most common error concerns improper sequence of cable connection for our pre-amplifiers with dedicated outboard power supplies. The last cable…

Ground Loops- (c) Kent English, Pass Labs Introduction Your brand new component is hooked up, fresh from the box, and the first time you power it up is a sonic disaster; it hums, it buzzes and in general sounds absolutely dreadful. Glaring at your equipment or dealer doesn’t help and twisting knobs only makes the noise worse; what now? From…

Super Symmetric Amplification- (c) 1998 Nelson Pass, Pass Labs U.S. Patent # 5376899 describes a new amplifying circuit topology that takes advantage of the character of special matched balanced amplifiers that are cross-coupled to provide cancellation of distortion and noise. The result provides high performance with very simple linear circuits, better than previous…

Single-Ended Class A- (c) Nelson Pass, Pass Labs Single-Ended Class A amplifiers have certainly hit it big in the four years since we began testing the first Aleph 0. So is this just another audio fad, or is there something fundamental about this kind of design, justifying a revival of the old approaches to amplification? When I started designing amplifiers…

Phase coherent crossover networks- by Nelson Pass drawings by Kirk Rader The importance of phase response in the audio chain has been brought to greater focus recently by equipment claims of phase coherency, (the output signal has the same phase relationships as the input signal). It is not particularly obvious that two different frequency components of a signal can…

SPEAKER CABLES: Science or Snake Oil- Speaker Builder, 2/1980 Nelson Pass AUDIOPHILES RECENTLY BEGAN re-examining the performance of every link in the audio playback chain, and before long their attention turned to the lowly loudspeaker cable. In response to demand, a number of companies are producing or distributing new and exotic cables claimed to improve audio power…

Cascode Amp Design- (c) Nelson Pass, Pass Labs Introduction Lowering distortion in power circuits without compromising their transient response remains a primary problem for designers of audio power amplifiers. Until fairly recently, the favorite technique for removing distortion components in linear amplifiers was to cascade many gain stages to form…