The first IC amplifier circuit cheap enough for consumer electronics was the Fairchild uA703, containing three transistors and used as an IF amplifier in FM receivers. Early ones were quite unreliable, often failing within a few hours of use. As production ramped and quality improved, Fairchild went on to more complex circuits. Fairchild’s ICs were made of silicon, whereas Texas Instruments was still using germanium, and not making as much progress. The uA709 operational amplifier or op-amp was a breakthrough part for audio. It brought a huge amount of gain over a wide bandwidth in a single small package for under $20.

The 709 was considered almost impossible to use by most engineers. It didn’t act like a transistor or tube. Until the IC op-amp, circuit design had always been about achieving enough gain with as few devices as possible because tubes and transistors were expensive and required dozens of surrounding resistors, capacitors, and transformers to function. With an op-amp, design emphasis shifted to controlling the gain and achieving a stable circuit. You need to consider the whole spectrum from DC to many megahertz, not just the audio band, because the basic device amplifies it all. Articles in electronic design publications tended to say things like “Don’t wonder whether your amplifier is oscillating, but rather at what frequency it’s oscillating, and whether you can live with that.”

The articles intrigued me enough to order four of the ICs from Beverly Electronics’ parts jobber. I was Service Manager at B.E. in 1968 when these early chips became available. I built a simple amplifier consisting of a 709 followed by two stages of emitter followers to get enough current to drive a speaker. Sure enough, I had a lot of trials and errors and a few fried output transistors before I found a combination of feedback and stabilization components that worked. It was my first design that responded to DC, and small signal response extended past 100 KHz, the limit of my test gear.

While limited in power output by the +/- 15V supply, distortion was extremely low, and the lack of roll off above and below the audio band meant that deep bass and treble were reproduced with little phase shift and attenuation. I knew from experience that I like wide bandwidth amplifiers, and this amp set my path in solid state amps. It served in my bedroom stereo for several years, but didn’t replace the H/K Citation Vs as my main amps. That required a couple more generations of solid state.