Peak images

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Creatives climb aspirational mountain peaks by building mental images: authors through words, composers through music, designers through styling, engineers through schematics.

The peak I aspired to climb as far back as the early 90s was solving the age old problem of volume controls. Every scheme to date was a compromise: the sliding dissimilar materials of pots, multiple contacts of stepped attenuators, irregularities of light dependent resistors, loss of sonics with electronic pots. None were perfect. All were flawed.

At that point in time, I had narrowed my design thoughts to a scheme with fewer compromises. Using nothing more than a single high-quality resistor for the sound to pass through, it would be possible to build a volume control that eliminated the contacts, distortion, moving parts, and sonic loss of prior art. After all, I reasoned, music passes through a number of resistors on its journey to the power amplifier. Why not one more?

The problem with resistors and sound quality concerns resistance levels. The greater the series resistance the signal passes through the worse music sounds. I won’t get into the particulars that any engineer reading this post would pick up upon—like the load the resistor is working into—but take my word for it. Passing music through a 100kΩ series resistor sounds much worse than through a 100Ω part. Sound quality losses are immediately apparent.

In order to make a volume control with a single series element, you need to keep that element’s resistance relatively high so the corresponding shunt elements that funnel unwanted volume away can be effective. That resistance wound up requiring 30kΩ in order to give the product a reasonable attenuation range using electronic switches for the shunt elements. 30k is a very high series resistance and we’d need something special to make that work.

The experiments to find the perfect part began as Arnie Nudell and I auditioned numerous brands and types of resistors, finally settling on one. It was a handcrafted Vishay that, at the time, cost us $30 each (when even the best were about a dime) and we would need two.

The single element scheme and the Vishay worked. The volume control sounded far better than any pot we had heard, including the much talked about Penny and Giles. The bad news was it still had a sound to it. Even without any shunt elements, the single 30kΩ $30 Vishay placed its sonic thumbprint on the music. But, it was the best we had at the time, and better than any other technology available to us. We used that volume control in a product we called the Stealth Amplifier, a massive 200 Watt per channel Class A integrated Genesis produced. But I wasn’t satisfied.

The hunt continued, the peak yet climbed. What could be simpler and cleaner sounding for a volume control than just a single resistor?