When we first came out with our original phono stage for $59.95 (complete with a money back guarantee), we were building the phono using integrated circuit op amps.
At that time there weren't many choices of op amps available to us, and the story of how we went from the classic 741 to the 301, and eventually wound up with one of the oldest and best sounding op amps, the 709C starts out with a bit of history.
In the early days of analog electronics, engineers were building circuits with individual transistors, resistors, and capacitors, all wired together by hand. These circuits were thought to be bulky, expensive, and often inconsistent in performance (at least that's what we were told...but it turns out to be the opposite for us high-end folks...so hang in there).
In any case, according to convention and what we knew at the time (1974) that all changed for the better with the invention of the integrated circuit. Jack Kilby of Texas Instruments first demonstrated the concept in 1958, followed by Robert Noyce of Fairchild Semiconductor in 1959. By placing multiple components on a single silicon chip, ICs revolutionized the industry, drastically reducing cost and size while improving reliability (all true).
This breakthrough set the stage for my personal hero, Bob Widlar, one of the most colorful and brilliant figures in the world of analog design. Working at Fairchild Semiconductor, Widlar developed the first commercially successful monolithic operational amplifier (op amp) in 1963, the µA702. But it was his next creation, the µA709, introduced in 1965, that truly changed the game.
The 709 was far ahead of its time in terms of speed and performance, becoming a staple in high-end applications. It had excellent high-frequency response and could handle complex analog tasks with precision. However, it came with two catches: the 709 required external compensation to maintain stability, making it tricky to work with, especially for less experienced engineers and it's output stage was class B, and needed help to become class A/B.
But, we weren't using the 709C (not yet). Instead, we were working with another op amp, the 741. The 741 was launched in 1968, and was designed by Dave Fullagar, also at Fairchild. The 741 was a more user-friendly alternative to the 709. It was stable, forgiving, and easy to implement, which made it an immediate success in the broader electronics world. Its simplicity and reliability made it the Swiss Army knife of op amps—ubiquitous in countless designs across industries. However, the 741 was significantly slower than Widlar’s 709. Its frequency response and slew rate were limited (a real dog), meaning it couldn’t match the 709's high-performance capabilities. But, at the time, we weren't working with the 709.
More to come tomorrow.
